                           Privoxy 3.0.8 User Manual

   [Copyright[ (c) 2001 - 2008 by Privoxy Developers]]

   $Id: user-manual.txt,v 1.76 2008/01/20 12:57:31 fabiankeil Exp $

   The Privoxy User Manual gives users information on how to install,
   configure and use Privoxy.

   Privoxy is a non-caching web proxy with advanced filtering capabilities
   for enhancing privacy, modifying web page data, managing HTTP cookies,
   controlling access, and removing ads, banners, pop-ups and other obnoxious
   Internet junk. Privoxy has a flexible configuration and can be customized
   to suit individual needs and tastes. Privoxy has application for both
   stand-alone systems and multi-user networks.

   Privoxy is based on Internet Junkbuster (tm).

   You can find the latest version of the Privoxy User Manual at
   http://www.privoxy.org/user-manual/. Please see the Contact section on how
   to contact the developers.

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   Table of Contents

   1. Introduction

                1.1. Features

   2. Installation

                2.1. Binary Packages

                             2.1.1. Red Hat and Fedora RPMs

                             2.1.2. Debian and Ubuntu

                             2.1.3. Windows

                             2.1.4. Solaris

                             2.1.5. OS/2

                             2.1.6. Mac OSX

                             2.1.7. AmigaOS

                             2.1.8. FreeBSD

                             2.1.9. Gentoo

                2.2. Building from Source

                2.3. Keeping your Installation Up-to-Date

   3. What's New in this Release

                3.1. Note to Upgraders

   4. Quickstart to Using Privoxy

                4.1. Quickstart to Ad Blocking

   5. Starting Privoxy

                5.1. Red Hat and Fedora

                5.2. Debian

                5.3. Windows

                5.4. Solaris, NetBSD, FreeBSD, HP-UX and others

                5.5. OS/2

                5.6. Mac OSX

                5.7. AmigaOS

                5.8. Gentoo

                5.9. Command Line Options

   6. Privoxy Configuration

                6.1. Controlling Privoxy with Your Web Browser

                6.2. Configuration Files Overview

   7. The Main Configuration File

                7.1. Local Set-up Documentation

                             7.1.1. user-manual

                             7.1.2. trust-info-url

                             7.1.3. admin-address

                             7.1.4. proxy-info-url

                7.2. Configuration and Log File Locations

                             7.2.1. confdir

                             7.2.2. templdir

                             7.2.3. logdir

                             7.2.4. actionsfile

                             7.2.5. filterfile

                             7.2.6. logfile

                             7.2.7. jarfile

                             7.2.8. trustfile

                7.3. Debugging

                             7.3.1. debug

                             7.3.2. single-threaded

                7.4. Access Control and Security

                             7.4.1. listen-address

                             7.4.2. toggle

                             7.4.3. enable-remote-toggle

                             7.4.4. enable-remote-http-toggle

                             7.4.5. enable-edit-actions

                             7.4.6. enforce-blocks

                             7.4.7. ACLs: permit-access and deny-access

                             7.4.8. buffer-limit

                7.5. Forwarding

                             7.5.1. forward

                             7.5.2. forward-socks4 and forward-socks4a

                             7.5.3. Advanced Forwarding Examples

                             7.5.4. forwarded-connect-retries

                             7.5.5. accept-intercepted-requests

                             7.5.6. allow-cgi-request-crunching

                             7.5.7. split-large-forms

                7.6. Windows GUI Options

   8. Actions Files

                8.1. Finding the Right Mix

                8.2. How to Edit

                8.3. How Actions are Applied to Requests

                8.4. Patterns

                             8.4.1. The Domain Pattern

                             8.4.2. The Path Pattern

                             8.4.3. The Tag Pattern

                8.5. Actions

                             8.5.1. add-header

                             8.5.2. block

                             8.5.3. client-header-filter

                             8.5.4. client-header-tagger

                             8.5.5. content-type-overwrite

                             8.5.6. crunch-client-header

                             8.5.7. crunch-if-none-match

                             8.5.8. crunch-incoming-cookies

                             8.5.9. crunch-server-header

                             8.5.10. crunch-outgoing-cookies

                             8.5.11. deanimate-gifs

                             8.5.12. downgrade-http-version

                             8.5.13. fast-redirects

                             8.5.14. filter

                             8.5.15. force-text-mode

                             8.5.16. forward-override

                             8.5.17. handle-as-empty-document

                             8.5.18. handle-as-image

                             8.5.19. hide-accept-language

                             8.5.20. hide-content-disposition

                             8.5.21. hide-if-modified-since

                             8.5.22. hide-forwarded-for-headers

                             8.5.23. hide-from-header

                             8.5.24. hide-referrer

                             8.5.25. hide-user-agent

                             8.5.26. inspect-jpegs

                             8.5.27. kill-popups

                             8.5.28. limit-connect

                             8.5.29. prevent-compression

                             8.5.30. overwrite-last-modified

                             8.5.31. redirect

                             8.5.32. send-vanilla-wafer

                             8.5.33. send-wafer

                             8.5.34. server-header-filter

                             8.5.35. server-header-tagger

                             8.5.36. session-cookies-only

                             8.5.37. set-image-blocker

                             8.5.38. treat-forbidden-connects-like-blocks

                             8.5.39. Summary

                8.6. Aliases

                8.7. Actions Files Tutorial

                             8.7.1. default.action

                             8.7.2. user.action

   9. Filter Files

                9.1. Filter File Tutorial

                9.2. The Pre-defined Filters

   10. Privoxy's Template Files

   11. Contacting the Developers, Bug Reporting and Feature Requests

                11.1. Get Support

                11.2. Reporting Problems

                             11.2.1. Reporting Ads or Other Configuration
                             Problems

                             11.2.2. Reporting Bugs

                11.3. Request New Features

                11.4. Other

   12. Privoxy Copyright, License and History

                12.1. License

                12.2. History

                12.3. Authors

   13. See Also

   14. Appendix

                14.1. Regular Expressions

                14.2. Privoxy's Internal Pages

                             14.2.1. Bookmarklets

                14.3. Chain of Events

                14.4. Troubleshooting: Anatomy of an Action

1. Introduction

   This documentation is included with the current stable version of Privoxy,
   v.3.0.8.

   --------------------------------------------------------------------------

  1.1. Features

   In addition to the core features of ad blocking and cookie management,
   Privoxy provides many supplemental features, that give the end-user more
   control, more privacy and more freedom:

     * Can be run as an "intercepting" proxy, which obviates the need to
       configure browsers individually.

     * Sophisticated actions and filters for manipulating both server and
       client headers.

     * Can be chained with other proxies.

     * Integrated browser based configuration and control utility at
       http://config.privoxy.org/ (shortcut: http://p.p/). Browser-based
       tracing of rule and filter effects. Remote toggling.

     * Web page filtering (text replacements, removes banners based on size,
       invisible "web-bugs", JavaScript and HTML annoyances, pop-up windows,
       etc.)

     * Modularized configuration that allows for standard settings and user
       settings to reside in separate files, so that installing updated
       actions files won't overwrite individual user settings.

     * Support for Perl Compatible Regular Expressions in the configuration
       files, and a more sophisticated and flexible configuration syntax.

     * Improved cookie management features (e.g. session based cookies).

     * GIF de-animation.

     * Bypass many click-tracking scripts (avoids script redirection).

     * Multi-threaded (POSIX and native threads).

     * User-customizable HTML templates for all proxy-generated pages (e.g.
       "blocked" page).

     * Auto-detection and re-reading of config file changes.

     * Improved signal handling, and a true daemon mode (Unix).

     * Every feature now controllable on a per-site or per-location basis,
       configuration more powerful and versatile over-all.

     * Many smaller new features added, limitations and bugs removed, and
       security holes fixed.

   --------------------------------------------------------------------------

2. Installation

   Privoxy is available both in convenient pre-compiled packages for a wide
   range of operating systems, and as raw source code. For most users, we
   recommend using the packages, which can be downloaded from our Privoxy
   Project Page.

   Note: On some platforms, the installer may remove previously installed
   versions, if found. (See below for your platform). In any case be sure to
   backup your old configuration if it is valuable to you. See the note to
   upgraders section below.

   --------------------------------------------------------------------------

  2.1. Binary Packages

   How to install the binary packages depends on your operating system:

   --------------------------------------------------------------------------

    2.1.1. Red Hat and Fedora RPMs

   RPMs can be installed with rpm -Uvh privoxy-3.0.8-1.rpm, and will use
   /etc/privoxy for the location of configuration files.

   Note that on Red Hat, Privoxy will not be automatically started on system
   boot. You will need to enable that using chkconfig, ntsysv, or similar
   methods.

   If you have problems with failed dependencies, try rebuilding the SRC RPM:
   rpm --rebuild privoxy-3.0.8-1.src.rpm. This will use your locally
   installed libraries and RPM version.

   Also note that if you have a Junkbuster RPM installed on your system, you
   need to remove it first, because the packages conflict. Otherwise, RPM
   will try to remove Junkbuster automatically if found, before installing
   Privoxy.

   --------------------------------------------------------------------------

    2.1.2. Debian and Ubuntu

   DEBs can be installed with apt-get install privoxy, and will use
   /etc/privoxy for the location of configuration files.

   --------------------------------------------------------------------------

    2.1.3. Windows

   Just double-click the installer, which will guide you through the
   installation process. You will find the configuration files in the same
   directory as you installed Privoxy in.

   Version 3.0.5 beta introduced full Windows service functionality. On
   Windows only, the Privoxy program has two new command line arguments to
   install and uninstall Privoxy as a service.

   Arguments:

           --install[:service_name]

           --uninstall[:service_name]

   After invoking Privoxy with --install, you will need to bring up the
   Windows service console to assign the user you want Privoxy to run under,
   and whether or not you want it to run whenever the system starts. You can
   start the Windows services console with the following command:
   services.msc. If you do not take the manual step of modifying Privoxy's
   service settings, it will not start. Note too that you will need to give
   Privoxy a user account that actually exists, or it will not be permitted
   to write to its log and configuration files.

   --------------------------------------------------------------------------

    2.1.4. Solaris

   Create a new directory, cd to it, then unzip and untar the archive. For
   the most part, you'll have to figure out where things go.

   --------------------------------------------------------------------------

    2.1.5. OS/2

   First, make sure that no previous installations of Junkbuster and / or
   Privoxy are left on your system. Check that no Junkbuster or Privoxy
   objects are in your startup folder.

   Then, just double-click the WarpIN self-installing archive, which will
   guide you through the installation process. A shadow of the Privoxy
   executable will be placed in your startup folder so it will start
   automatically whenever OS/2 starts.

   The directory you choose to install Privoxy into will contain all of the
   configuration files.

   --------------------------------------------------------------------------

    2.1.6. Mac OSX

   Unzip the downloaded file (you can either double-click on the file from
   the finder, or from the desktop if you downloaded it there). Then,
   double-click on the package installer icon named Privoxy.pkg and follow
   the installation process. Privoxy will be installed in the folder
   /Library/Privoxy. It will start automatically whenever you start up. To
   prevent it from starting automatically, remove or rename the folder
   /Library/StartupItems/Privoxy.

   To start Privoxy by hand, double-click on StartPrivoxy.command in the
   /Library/Privoxy folder. Or, type this command in the Terminal:

     /Library/Privoxy/StartPrivoxy.command


   You will be prompted for the administrator password.

   --------------------------------------------------------------------------

    2.1.7. AmigaOS

   Copy and then unpack the lha archive to a suitable location. All necessary
   files will be installed into Privoxy directory, including all
   configuration and log files. To uninstall, just remove this directory.

   --------------------------------------------------------------------------

    2.1.8. FreeBSD

   Privoxy is part of FreeBSD's Ports Collection, you can build and install
   it with cd /usr/ports/www/privoxy; make install clean.

   If you don't use the ports, you can fetch and install the package with
   pkg_add -r privoxy.

   The port skeleton and the package can also be downloaded from the File
   Release Page, but there's no reason to use them unless you're interested
   in the beta releases which are only available there.

   --------------------------------------------------------------------------

    2.1.9. Gentoo

   Gentoo source packages (Ebuilds) for Privoxy are contained in the Gentoo
   Portage Tree (they are not on the download page, but there is a Gentoo
   section, where you can see when a new Privoxy Version is added to the
   Portage Tree).

   Before installing Privoxy under Gentoo just do first emerge rsync to get
   the latest changes from the Portage tree. With emerge privoxy you install
   the latest version.

   Configuration files are in /etc/privoxy, the documentation is in
   /usr/share/doc/privoxy-3.0.8 and the Log directory is in /var/log/privoxy.

   --------------------------------------------------------------------------

  2.2. Building from Source

   The most convenient way to obtain the Privoxy sources is to download the
   source tarball from our project download page.

   If you like to live on the bleeding edge and are not afraid of using
   possibly unstable development versions, you can check out the
   up-to-the-minute version directly from the CVS repository.

   To build Privoxy from source, autoconf, GNU make (gmake), and, of course,
   a C compiler like gcc are required.

   When building from a source tarball, first unpack the source:

    tar xzvf privoxy-3.0.8-src* [.tgz or .tar.gz]
    cd privoxy-3.0.8

   For retrieving the current CVS sources, you'll need a CVS client
   installed. Note that sources from CVS are typically development quality,
   and may not be stable, or well tested. To download CVS source, check the
   Sourceforge documentation, which might give commands like:

  cvs -d:pserver:anonymous@ijbswa.cvs.sourceforge.net:/cvsroot/ijbswa login
  cvs -z3 -d:pserver:anonymous@ijbswa.cvs.sourceforge.net:/cvsroot/ijbswa co current
  cd current

   This will create a directory named current/, which will contain the source
   tree.

   You can also check out any Privoxy "branch", just exchange the current
   name with the wanted branch name (Example: v_3_0_branch for the 3.0 cvs
   tree).

   It is also strongly recommended to not run Privoxy as root. You should
   configure/install/run Privoxy as an unprivileged user, preferably by
   creating a "privoxy" user and group just for this purpose. See your local
   documentation for the correct command line to do add new users and groups
   (something like adduser, but the command syntax may vary from platform to
   platform).

   /etc/passwd might then look like:

     privoxy:*:7777:7777:privoxy proxy:/no/home:/no/shell

   And then /etc/group, like:

     privoxy:*:7777:

   Some binary packages may do this for you.

   Then, to build from either unpacked tarball or CVS source:

    autoheader
    autoconf
    ./configure      # (--help to see options)
    make             # (the make from GNU, sometimes called gmake)
    su               # Possibly required
    make -n install  # (to see where all the files will go)
    make -s install  # (to really install, -s to silence output)

   Using GNU make, you can have the first four steps automatically done for
   you by just typing:

     make

   in the freshly downloaded or unpacked source directory.

   To build an executable with security enhanced features so that users
   cannot easily bypass the proxy (e.g. "Go There Anyway"), or alter their
   own configurations, configure like this:

    ./configure  --disable-toggle  --disable-editor  --disable-force

   Then build as above. In Privoxy 3.0.7 and later, all of these options can
   also be disabled through the configuration file.

   WARNING: If installing as root, the install will fail unless a non-root
   user or group is specified, or a privoxy user and group already exist on
   the system. If a non-root user is specified, and no group, then the
   installation will try to also use a group of the same name as "user". If a
   group is specified (and no user), then the support files will be installed
   as writable by that group, and owned by the user running the installation.

   configure accepts --with-user and --with-group options for setting user
   and group ownership of the configuration files (which need to be writable
   by the daemon). The specified user must already exist. When starting
   Privoxy, it must be run as this same user to insure write access to
   configuration and log files!

   Alternately, you can specify user and group on the make command line, but
   be sure both already exist:

    make -s install  USER=privoxy GROUP=privoxy

   The default installation path for make install is /usr/local. This may of
   course be customized with the various ./configure path options. If you are
   doing an install to anywhere besides /usr/local, be sure to set the
   appropriate paths with the correct configure options (./configure --help).
   Non-privileged users must of course have write access permissions to
   wherever the target installation is going.

   If you do install to /usr/local, the install will use
   sysconfdir=$prefix/etc/privoxy by default. All other destinations, and the
   direct usage of --sysconfdir flag behave like normal, i.e. will not add
   the extra privoxy directory. This is for a safer install, as there may
   already exist another program that uses a file with the "config" name, and
   thus makes /usr/local/etc cleaner.

   If installing to /usr/local, the documentation will go by default to
   $prefix/share/doc. But if this directory doesn't exist, it will then try
   $prefix/doc and install there before creating a new $prefix/share/doc just
   for Privoxy.

   Again, if the installs goes to /usr/local, the localstatedir (ie: var/)
   will default to /var instead of $prefix/var so the logs will go to
   /var/log/privoxy/, and the pid file will be created in
   /var/run/privoxy.pid.

   make install will attempt to set the correct values in config (main
   configuration file). You should check this to make sure all values are
   correct. If appropriate, an init script will be installed, but it is up to
   the user to determine how and where to start Privoxy. The init script
   should be checked for correct paths and values, if anything other than a
   default install is done.

   If install finds previous versions of local configuration files, most of
   these will not be overwritten, and the new ones will be installed with a
   "new" extension. default.action, default.filter, and standard.action will
   be overwritten. You will then need to manually update the other installed
   configuration files as needed. The default template files will be
   overwritten. If you have customized, local templates, these should be
   stored safely in a separate directory and defined in config by the
   "templdir" directive. It is of course wise to always back-up any important
   configuration files "just in case". If a previous version of Privoxy is
   already running, you will have to restart it manually.

   For more detailed instructions on how to build Redhat RPMs, Windows
   self-extracting installers, building on platforms with special
   requirements etc, please consult the developer manual.

   --------------------------------------------------------------------------

  2.3. Keeping your Installation Up-to-Date

   As user feedback comes in and development continues, we will make updated
   versions of both the main actions file (as a separate package) and the
   software itself (including the actions file) available for download.

   If you wish to receive an email notification whenever we release updates
   of Privoxy or the actions file, subscribe to our announce mailing list,
   ijbswa-announce@lists.sourceforge.net.

   In order not to lose your personal changes and adjustments when updating
   to the latest default.action file we strongly recommend that you use
   user.action and user.filter for your local customizations of Privoxy. See
   the Chapter on actions files for details.

   --------------------------------------------------------------------------

3. What's New in this Release

   There are many improvements and new features since Privoxy 3.0.6, the last
   stable release:

     * Two new actions server-header-tagger and client-header-tagger that can
       be used to create arbitrary "tags" based on client and server headers.
       These "tags" can then subsequently be used to control the other
       actions used for the current request, greatly increasing Privoxy's
       flexibility and selectivity. See tag patterns for more information on
       tags.

     * Header filtering is done with dedicated header filters now. As a
       result the actions "filter-client-headers" and "filter-server-headers"
       that were introduced with Privoxy 3.0.5 to apply content filters to
       the headers have been removed. See the new actions
       server-header-filter and client-header-filter for details.

     * There are four new options for the main config file:

          * allow-cgi-request-crunching which allows requests for Privoxy's
            internal CGI pages to be blocked, redirected or (un)trusted like
            ordinary requests.

          * split-large-forms that will work around a browser bug that caused
            IE6 and IE7 to ignore the Submit button on the Privoxy's
            edit-actions-for-url CGI page.

          * accept-intercepted-requests which allows to combine Privoxy with
            any packet filter to create an intercepting proxy for HTTP/1.1
            requests (and for HTTP/1.0 requests with Host header set). This
            means clients can be forced to use Privoxy even if their proxy
            settings are configured differently.

          * templdir to designate an alternate location for Privoxy's locally
            customized CGI templates so that these are not overwritten during
            upgrades.

     * A new command line option --pre-chroot-nslookup hostname to initialize
       the resolver library before chroot'ing. On some systems this reduces
       the number of files that must be copied into the chroot tree. (Patch
       provided by Stephen Gildea)

     * The forward-override action allows changing of the forwarding settings
       through the actions files. Combined with tags, this allows to choose
       the forwarder based on client headers like the User-Agent, or the
       request origin.

     * The redirect action can now use regular expression substitutions
       against the original URL.

     * zlib support is now available as a compile time option to filter
       compressed content. Patch provided by Wil Mahan.

     * Improve various filters, and add new ones.

     * Include support for RFC 3253 so that Subversion works with Privoxy.
       Patch provided by Petr Kadlec.

     * Logging can be completely turned off by not specifying a logfile
       directive.

     * A number of improvements to Privoxy's internal CGI pages, including
       the use of favicons for error and control pages.

     * Many bugfixes, memory leaks addressed, code improvements, and logging
       improvements.

   For a more detailed list of changes please have a look at the ChangeLog.

   --------------------------------------------------------------------------

  3.1. Note to Upgraders

   A quick list of things to be aware of before upgrading from earlier
   versions of Privoxy:

     * The recommended way to upgrade Privoxy is to backup your old
       configuration files, install the new ones, verify that Privoxy is
       working correctly and finally merge back your changes using diff and
       maybe patch.

       There are a number of new features in each Privoxy release and most of
       them have to be explicitly enabled in the configuration files. Old
       configuration files obviously don't do that and due to syntax changes
       using old configuration files with a new Privoxy isn't always possible
       anyway.

     * Note that some installers remove earlier versions completely,
       including configuration files, therefore you should really save any
       important configuration files!

     * On the other hand, other installers don't overwrite existing
       configuration files, thinking you will want to do that yourself.

     * standard.action now only includes the enabled actions. Not all actions
       as before.

     * In the default configuration only fatal errors are logged now. You can
       change that in the debug section of the configuration file. You may
       also want to enable more verbose logging until you verified that the
       new Privoxy version is working as expected.

     * Three other config file settings are now off by default:
       enable-remote-toggle, enable-remote-http-toggle, and
       enable-edit-actions. If you use or want these, you will need to
       explicitly enable them, and be aware of the security issues involved.

     * The "filter-client-headers" and "filter-server-headers" actions that
       were introduced with Privoxy 3.0.5 to apply content filters to the
       headers have been removed and replaced with new actions. See the
       What's New section above.

   --------------------------------------------------------------------------

4. Quickstart to Using Privoxy

     * Install Privoxy. See the Installation Section below for platform
       specific information.

     * Advanced users and those who want to offer Privoxy service to more
       than just their local machine should check the main config file,
       especially the security-relevant options. These are off by default.

     * Start Privoxy, if the installation program has not done this already
       (may vary according to platform). See the section Starting Privoxy.

     * Set your browser to use Privoxy as HTTP and HTTPS (SSL) proxy by
       setting the proxy configuration for address of 127.0.0.1 and port
       8118. DO NOT activate proxying for FTP or any protocols besides HTTP
       and HTTPS (SSL) unless you intend to prevent your browser from using
       these protocols.

     * Flush your browser's disk and memory caches, to remove any cached ad
       images. If using Privoxy to manage cookies, you should remove any
       currently stored cookies too.

     * A default installation should provide a reasonable starting point for
       most. There will undoubtedly be occasions where you will want to
       adjust the configuration, but that can be dealt with as the need
       arises. Little to no initial configuration is required in most cases,
       you may want to enable the web-based action editor though. Be sure to
       read the warnings first.

       See the Configuration section for more configuration options, and how
       to customize your installation. You might also want to look at the
       next section for a quick introduction to how Privoxy blocks ads and
       banners.

     * If you experience ads that slip through, innocent images that are
       blocked, or otherwise feel the need to fine-tune Privoxy's behavior,
       take a look at the actions files. As a quick start, you might find the
       richly commented examples helpful. You can also view and edit the
       actions files through the web-based user interface. The Appendix
       "Troubleshooting: Anatomy of an Action" has hints on how to understand
       and debug actions that "misbehave".

     * Please see the section Contacting the Developers on how to report
       bugs, problems with websites or to get help.

     * Now enjoy surfing with enhanced control, comfort and privacy!

   --------------------------------------------------------------------------

  4.1. Quickstart to Ad Blocking

   Ad blocking is but one of Privoxy's array of features. Many of these
   features are for the technically minded advanced user. But, ad and banner
   blocking is surely common ground for everybody.

   This section will provide a quick summary of ad blocking so you can get up
   to speed quickly without having to read the more extensive information
   provided below, though this is highly recommended.

   First a bit of a warning ... blocking ads is much like blocking SPAM: the
   more aggressive you are about it, the more likely you are to block things
   that were not intended. And the more likely that some things may not work
   as intended. So there is a trade off here. If you want extreme ad free
   browsing, be prepared to deal with more "problem" sites, and to spend more
   time adjusting the configuration to solve these unintended consequences.
   In short, there is not an easy way to eliminate all ads. Either take the
   easy way and settle for most ads blocked with the default configuration,
   or jump in and tweak it for your personal surfing habits and preferences.

   Secondly, a brief explanation of Privoxy's "actions". "Actions" in this
   context, are the directives we use to tell Privoxy to perform some task
   relating to HTTP transactions (i.e. web browsing). We tell Privoxy to take
   some "action". Each action has a unique name and function. While there are
   many potential actions in Privoxy's arsenal, only a few are used for ad
   blocking. Actions, and action configuration files, are explained in depth
   below.

   Actions are specified in Privoxy's configuration, followed by one or more
   URLs to which the action should apply. URLs can actually be URL type
   patterns that use wildcards so they can apply potentially to a range of
   similar URLs. The actions, together with the URL patterns are called a
   section.

   When you connect to a website, the full URL will either match one or more
   of the sections as defined in Privoxy's configuration, or not. If so, then
   Privoxy will perform the respective actions. If not, then nothing special
   happens. Furthermore, web pages may contain embedded, secondary URLs that
   your web browser will use to load additional components of the page, as it
   parses the original page's HTML content. An ad image for instance, is just
   an URL embedded in the page somewhere. The image itself may be on the same
   server, or a server somewhere else on the Internet. Complex web pages will
   have many such embedded URLs. Privoxy can deal with each URL individually,
   so, for instance, the main page text is not touched, but images from
   such-and-such server are blocked.

   The most important actions for basic ad blocking are: block,
   handle-as-image, handle-as-empty-document,and set-image-blocker:

     * block - this is perhaps the single most used action, and is
       particularly important for ad blocking. This action stops any contact
       between your browser and any URL patterns that match this action's
       configuration. It can be used for blocking ads, but also anything that
       is determined to be unwanted. By itself, it simply stops any
       communication with the remote server and sends Privoxy's own built-in
       BLOCKED page instead to let you now what has happened (with some
       exceptions, see below).

     * handle-as-image - tells Privoxy to treat this URL as an image.
       Privoxy's default configuration already does this for all common image
       types (e.g. GIF), but there are many situations where this is not so
       easy to determine. So we'll force it in these cases. This is
       particularly important for ad blocking, since only if we know that
       it's an image of some kind, can we replace it with an image of our
       choosing, instead of the Privoxy BLOCKED page (which would only result
       in a "broken image" icon). There are some limitations to this though.
       For instance, you can't just brute-force an image substitution for an
       entire HTML page in most situations.

     * handle-as-empty-document - sends an empty document instead of
       Privoxy's normal BLOCKED HTML page. This is useful for file types that
       are neither HTML nor images, such as blocking JavaScript files.

     * set-image-blocker - tells Privoxy what to display in place of an ad
       image that has hit a block rule. For this to come into play, the URL
       must match a block action somewhere in the configuration, and, it must
       also match an handle-as-image action.

       The configuration options on what to display instead of the ad are:

       pattern - a checkerboard pattern, so that an ad replacement is
       obvious. This is the default.

       blank - A very small empty GIF image is displayed. This is the
       so-called "invisible" configuration option.

       http://<URL> - A redirect to any image anywhere of the user's
       choosing (advanced usage).

   Advanced users will eventually want to explore Privoxy filters as well.
   Filters are very different from blocks. A "block" blocks a site, page, or
   unwanted contented. Filters are a way of filtering or modifying what is
   actually on the page. An example filter usage: a text replacement of
   "no-no" for "nasty-word". That is a very simple example. This process can
   be used for ad blocking, but it is more in the realm of advanced usage and
   has some pitfalls to be wary off.

   The quickest way to adjust any of these settings is with your browser
   through the special Privoxy editor at
   http://config.privoxy.org/show-status (shortcut: http://p.p/show-status).
   This is an internal page, and does not require Internet access.

   Note that as of Privoxy 3.0.7 beta the action editor is disabled by
   default. Check the enable-edit-actions section in the configuration file
   to learn why and in which cases it's safe to enable again.

   If you decided to enable the action editor, select the appropriate
   "actions" file, and click "Edit". It is best to put personal or local
   preferences in user.action since this is not meant to be overwritten
   during upgrades, and will over-ride the settings in other files. Here you
   can insert new "actions", and URLs for ad blocking or other purposes, and
   make other adjustments to the configuration. Privoxy will detect these
   changes automatically.

   A quick and simple step by step example:

     * Right click on the ad image to be blocked, then select "Copy Link
       Location" from the pop-up menu.

     * Set your browser to http://config.privoxy.org/show-status

     * Find user.action in the top section, and click on "Edit":

       Figure 1. Actions Files in Use

     * You should have a section with only block listed under "Actions:". If
       not, click a "Insert new section below" button, and in the new section
       that just appeared, click the Edit button right under the word
       "Actions:". This will bring up a list of all actions. Find block near
       the top, and click in the "Enabled" column, then "Submit" just below
       the list.

     * Now, in the block actions section, click the "Add" button, and paste
       the URL the browser got from "Copy Link Location". Remove the http://
       at the beginning of the URL. Then, click "Submit" (or "OK" if in a
       pop-up window).

     * Now go back to the original page, and press SHIFT-Reload (or flush all
       browser caches). The image should be gone now.

   This is a very crude and simple example. There might be good reasons to
   use a wildcard pattern match to include potentially similar images from
   the same site. For a more extensive explanation of "patterns", and the
   entire actions concept, see the Actions section.

   For advanced users who want to hand edit their config files, you might
   want to now go to the Actions Files Tutorial. The ideas explained therein
   also apply to the web-based editor.

   There are also various filters that can be used for ad blocking (filters
   are a special subset of actions). These fall into the "advanced" usage
   category, and are explained in depth in later sections.

   --------------------------------------------------------------------------

5. Starting Privoxy

   Before launching Privoxy for the first time, you will want to configure
   your browser(s) to use Privoxy as a HTTP and HTTPS (SSL) proxy. The
   default is 127.0.0.1 (or localhost) for the proxy address, and port 8118
   (earlier versions used port 8000). This is the one configuration step that
   must be done!

   Please note that Privoxy can only proxy HTTP and HTTPS traffic. It will
   not work with FTP or other protocols.

   Figure 2. Proxy Configuration Showing Mozilla/Netscape HTTP and HTTPS
   (SSL) Settings

   With Firefox, this is typically set under:

    Tools -> Options ->  Advanced -> Network ->Connection -> Settings


   Or optionally on some platforms:

    Edit -> Preferences -> General -> Connection Settings -> Manual Proxy
   Configuration


   With Netscape (and Mozilla), this can be set under:

    Edit -> Preferences -> Advanced -> Proxies -> HTTP Proxy


   For Internet Explorer v.5-7:

    Tools -> Internet Options -> Connections -> LAN Settings

   Then, check "Use Proxy" and fill in the appropriate info (Address:
   127.0.0.1, Port: 8118). Include HTTPS (SSL), if you want HTTPS proxy
   support too (sometimes labeled "Secure"). Make sure any checkboxes like
   "Use the same proxy server for all protocols" is UNCHECKED. You want only
   HTTP and HTTPS (SSL)!

   Figure 3. Proxy Configuration Showing Internet Explorer HTTP and HTTPS
   (Secure) Settings

   After doing this, flush your browser's disk and memory caches to force a
   re-reading of all pages and to get rid of any ads that may be cached.
   Remove any cookies, if you want Privoxy to manage that. You are now ready
   to start enjoying the benefits of using Privoxy!

   Privoxy itself is typically started by specifying the main configuration
   file to be used on the command line. If no configuration file is specified
   on the command line, Privoxy will look for a file named config in the
   current directory. Except on Win32 where it will try config.txt.

   --------------------------------------------------------------------------

  5.1. Red Hat and Fedora

   A default Red Hat installation may not start Privoxy upon boot. It will
   use the file /etc/privoxy/config as its main configuration file.

    # /etc/rc.d/init.d/privoxy start

   Or ...

    # service privoxy start

   --------------------------------------------------------------------------

  5.2. Debian

   We use a script. Note that Debian typically starts Privoxy upon booting
   per default. It will use the file /etc/privoxy/config as its main
   configuration file.

    # /etc/init.d/privoxy start

   --------------------------------------------------------------------------

  5.3. Windows

   Click on the Privoxy Icon to start Privoxy. If no configuration file is
   specified on the command line, Privoxy will look for a file named
   config.txt. Note that Windows will automatically start Privoxy when the
   system starts if you chose that option when installing.

   Privoxy can run with full Windows service functionality. On Windows only,
   the Privoxy program has two new command line arguments to install and
   uninstall Privoxy as a service. See the Windows Installation instructions
   for details.

   --------------------------------------------------------------------------

  5.4. Solaris, NetBSD, FreeBSD, HP-UX and others

   Example Unix startup command:

    # /usr/sbin/privoxy /etc/privoxy/config

   --------------------------------------------------------------------------

  5.5. OS/2

   During installation, Privoxy is configured to start automatically when the
   system restarts. You can start it manually by double-clicking on the
   Privoxy icon in the Privoxy folder.

   --------------------------------------------------------------------------

  5.6. Mac OSX

   During installation, Privoxy is configured to start automatically when the
   system restarts. To start Privoxy manually, double-click on the
   StartPrivoxy.command icon in the /Library/Privoxy folder. Or, type this
   command in the Terminal:

     /Library/Privoxy/StartPrivoxy.command


   You will be prompted for the administrator password.

   --------------------------------------------------------------------------

  5.7. AmigaOS

   Start Privoxy (with RUN <>NIL:) in your startnet script (AmiTCP), in
   s:user-startup (RoadShow), as startup program in your startup script
   (Genesis), or as startup action (Miami and MiamiDx). Privoxy will
   automatically quit when you quit your TCP/IP stack (just ignore the
   harmless warning your TCP/IP stack may display that Privoxy is still
   running).

   --------------------------------------------------------------------------

  5.8. Gentoo

   A script is again used. It will use the file /etc/privoxy/config as its
   main configuration file.

    /etc/init.d/privoxy start


   Note that Privoxy is not automatically started at boot time by default.
   You can change this with the rc-update command.

    rc-update add privoxy default


   --------------------------------------------------------------------------

  5.9. Command Line Options

   Privoxy may be invoked with the following command-line options:

     * --version

       Print version info and exit. Unix only.

     * --help

       Print short usage info and exit. Unix only.

     * --no-daemon

       Don't become a daemon, i.e. don't fork and become process group
       leader, and don't detach from controlling tty. Unix only.

     * --pidfile FILE

       On startup, write the process ID to FILE. Delete the FILE on exit.
       Failure to create or delete the FILE is non-fatal. If no FILE option
       is given, no PID file will be used. Unix only.

     * --user USER[.GROUP]

       After (optionally) writing the PID file, assume the user ID of USER,
       and if included the GID of GROUP. Exit if the privileges are not
       sufficient to do so. Unix only.

     * --chroot

       Before changing to the user ID given in the --user option, chroot to
       that user's home directory, i.e. make the kernel pretend to the
       Privoxy process that the directory tree starts there. If set up
       carefully, this can limit the impact of possible vulnerabilities in
       Privoxy to the files contained in that hierarchy. Unix only.

     * --pre-chroot-nslookup hostname

       Specifies a hostname to look up before doing a chroot. On some
       systems, initializing the resolver library involves reading config
       files from /etc and/or loading additional shared libraries from /lib.
       On these systems, doing a hostname lookup before the chroot reduces
       the number of files that must be copied into the chroot tree.

       For fastest startup speed, a good value is a hostname that is not in
       /etc/hosts but that your local name server (listed in
       /etc/resolv.conf) can resolve without recursion (that is, without
       having to ask any other name servers). The hostname need not exist,
       but if it doesn't, an error message (which can be ignored) will be
       output.

     * configfile

       If no configfile is included on the command line, Privoxy will look
       for a file named "config" in the current directory (except on Win32
       where it will look for "config.txt" instead). Specify full path to
       avoid confusion. If no config file is found, Privoxy will fail to
       start.

   On MS Windows only there are two additional command-line options to allow
   Privoxy to install and run as a service. See the Window Installation
   section for details.

   --------------------------------------------------------------------------

6. Privoxy Configuration

   All Privoxy configuration is stored in text files. These files can be
   edited with a text editor. Many important aspects of Privoxy can also be
   controlled easily with a web browser.

   --------------------------------------------------------------------------

  6.1. Controlling Privoxy with Your Web Browser

   Privoxy's user interface can be reached through the special URL
   http://config.privoxy.org/ (shortcut: http://p.p/), which is a built-in
   page and works without Internet access. You will see the following
   section:



   Privoxy Menu

     View & change the current configuration

     View the source code version numbers

     View the request headers.

     Look up which actions apply to a URL and why

     Toggle Privoxy on or off

     Documentation


   This should be self-explanatory. Note the first item leads to an editor
   for the actions files, which is where the ad, banner, cookie, and URL
   blocking magic is configured as well as other advanced features of
   Privoxy. This is an easy way to adjust various aspects of Privoxy
   configuration. The actions file, and other configuration files, are
   explained in detail below.

   "Toggle Privoxy On or Off" is handy for sites that might have problems
   with your current actions and filters. You can in fact use it as a test to
   see whether it is Privoxy causing the problem or not. Privoxy continues to
   run as a proxy in this case, but all manipulation is disabled, i.e.
   Privoxy acts like a normal forwarding proxy. There is even a toggle
   Bookmarklet offered, so that you can toggle Privoxy with one click from
   your browser.

   Note that several of the features described above are disabled by default
   in Privoxy 3.0.7 beta and later. Check the configuration file to learn why
   and in which cases it's safe to enable them again.

   --------------------------------------------------------------------------

  6.2. Configuration Files Overview

   For Unix, *BSD and Linux, all configuration files are located in
   /etc/privoxy/ by default. For MS Windows, OS/2, and AmigaOS these are all
   in the same directory as the Privoxy executable.

   The installed defaults provide a reasonable starting point, though some
   settings may be aggressive by some standards. For the time being, the
   principle configuration files are:

     * The main configuration file is named config on Linux, Unix, BSD, OS/2,
       and AmigaOS and config.txt on Windows. This is a required file.

     * default.action (the main actions file) is used to define which
       "actions" relating to banner-blocking, images, pop-ups, content
       modification, cookie handling etc should be applied by default. It
       also defines many exceptions (both positive and negative) from this
       default set of actions that enable Privoxy to selectively eliminate
       the junk, and only the junk, on as many websites as possible.

       Multiple actions files may be defined in config. These are processed
       in the order they are defined. Local customizations and locally
       preferred exceptions to the default policies as defined in
       default.action (which you will most probably want to define sooner or
       later) are probably best applied in user.action, where you can
       preserve them across upgrades. standard.action is only for Privoxy's
       internal use.

       There is also a web based editor that can be accessed from
       http://config.privoxy.org/show-status (Shortcut:
       http://p.p/show-status) for the various actions files.

     * "Filter files" (the filter file) can be used to re-write the raw page
       content, including viewable text as well as embedded HTML and
       JavaScript, and whatever else lurks on any given web page. The
       filtering jobs are only pre-defined here; whether to apply them or not
       is up to the actions files. default.filter includes various filters
       made available for use by the developers. Some are much more intrusive
       than others, and all should be used with caution. You may define
       additional filter files in config as you can with actions files. We
       suggest user.filter for any locally defined filters or customizations.

   The syntax of the configuration and filter files may change between
   different Privoxy versions, unfortunately some enhancements cost backwards
   compatibility.

   All files use the "#" character to denote a comment (the rest of the line
   will be ignored) and understand line continuation through placing a
   backslash ("\") as the very last character in a line. If the # is preceded
   by a backslash, it looses its special function. Placing a # in front of an
   otherwise valid configuration line to prevent it from being interpreted is
   called "commenting out" that line. Blank lines are ignored.

   The actions files and filter files can use Perl style regular expressions
   for maximum flexibility.

   After making any changes, there is no need to restart Privoxy in order for
   the changes to take effect. Privoxy detects such changes automatically.
   Note, however, that it may take one or two additional requests for the
   change to take effect. When changing the listening address of Privoxy,
   these "wake up" requests must obviously be sent to the old listening
   address.

   --------------------------------------------------------------------------

7. The Main Configuration File

   Again, the main configuration file is named config on Linux/Unix/BSD and
   OS/2, and config.txt on Windows. Configuration lines consist of an initial
   keyword followed by a list of values, all separated by whitespace (any
   number of spaces or tabs). For example:

     confdir /etc/privoxy

   Assigns the value /etc/privoxy to the option confdir and thus indicates
   that the configuration directory is named "/etc/privoxy/".

   All options in the config file except for confdir and logdir are optional.
   Watch out in the below description for what happens if you leave them
   unset.

   The main config file controls all aspects of Privoxy's operation that are
   not location dependent (i.e. they apply universally, no matter where you
   may be surfing).

   --------------------------------------------------------------------------

  7.1. Local Set-up Documentation

   If you intend to operate Privoxy for more users than just yourself, it
   might be a good idea to let them know how to reach you, what you block and
   why you do that, your policies, etc.

   --------------------------------------------------------------------------

      7.1.1. user-manual

   Specifies:

           Location of the Privoxy User Manual.

   Type of value:

           A fully qualified URI

   Default value:

           Unset

   Effect if unset:

           http://www.privoxy.org/version/user-manual/ will be used, where
           version is the Privoxy version.

   Notes:

           The User Manual URI is the single best source of information on
           Privoxy, and is used for help links from some of the internal CGI
           pages. The manual itself is normally packaged with the binary
           distributions, so you probably want to set this to a locally
           installed copy.

           Examples:

           The best all purpose solution is simply to put the full local PATH
           to where the User Manual is located:

           user-manual /usr/share/doc/privoxy/user-manual

           The User Manual is then available to anyone with access to
           Privoxy, by following the built-in URL:
           http://config.privoxy.org/user-manual/ (or the shortcut:
           http://p.p/user-manual/).

           If the documentation is not on the local system, it can be
           accessed from a remote server, as:

           user-manual http://example.com/privoxy/user-manual/

           +---------------------------------------------------------+
           |                         Warning                         |
           |---------------------------------------------------------|
           | If set, this option should be the first option in the   |
           | config file, because it is used while the config file   |
           | is being read on start-up.                              |
           +---------------------------------------------------------+

   --------------------------------------------------------------------------

      7.1.2. trust-info-url

   Specifies:

           A URL to be displayed in the error page that users will see if
           access to an untrusted page is denied.

   Type of value:

           URL

   Default value:

           Two example URLs are provided

   Effect if unset:

           No links are displayed on the "untrusted" error page.

   Notes:

           The value of this option only matters if the experimental trust
           mechanism has been activated. (See trustfile below.)

           If you use the trust mechanism, it is a good idea to write up some
           on-line documentation about your trust policy and to specify the
           URL(s) here. Use multiple times for multiple URLs.

           The URL(s) should be added to the trustfile as well, so users
           don't end up locked out from the information on why they were
           locked out in the first place!

   --------------------------------------------------------------------------

      7.1.3. admin-address

   Specifies:

           An email address to reach the Privoxy administrator.

   Type of value:

           Email address

   Default value:

           Unset

   Effect if unset:

           No email address is displayed on error pages and the CGI user
           interface.

   Notes:

           If both admin-address and proxy-info-url are unset, the whole
           "Local Privoxy Support" box on all generated pages will not be
           shown.

   --------------------------------------------------------------------------

      7.1.4. proxy-info-url

   Specifies:

           A URL to documentation about the local Privoxy setup,
           configuration or policies.

   Type of value:

           URL

   Default value:

           Unset

   Effect if unset:

           No link to local documentation is displayed on error pages and the
           CGI user interface.

   Notes:

           If both admin-address and proxy-info-url are unset, the whole
           "Local Privoxy Support" box on all generated pages will not be
           shown.

           This URL shouldn't be blocked ;-)

   --------------------------------------------------------------------------

  7.2. Configuration and Log File Locations

   Privoxy can (and normally does) use a number of other files for additional
   configuration, help and logging. This section of the configuration file
   tells Privoxy where to find those other files.

   The user running Privoxy, must have read permission for all configuration
   files, and write permission to any files that would be modified, such as
   log files and actions files.

   --------------------------------------------------------------------------

      7.2.1. confdir

   Specifies:

           The directory where the other configuration files are located.

   Type of value:

           Path name

   Default value:

           /etc/privoxy (Unix) or Privoxy installation dir (Windows)

   Effect if unset:

           Mandatory

   Notes:

           No trailing "/", please.

   --------------------------------------------------------------------------

      7.2.2. templdir

   Specifies:

           An alternative directory where the templates are loaded from.

   Type of value:

           Path name

   Default value:

           unset

   Effect if unset:

           The templates are assumed to be located in confdir/template.

   Notes:

           Privoxy's original templates are usually overwritten with each
           update. Use this option to relocate customized templates that
           should be kept. As template variables might change between
           updates, you shouldn't expect templates to work with Privoxy
           releases other than the one they were part of, though.

   --------------------------------------------------------------------------

      7.2.3. logdir

   Specifies:

           The directory where all logging takes place (i.e. where logfile
           and jarfile are located).

   Type of value:

           Path name

   Default value:

           /var/log/privoxy (Unix) or Privoxy installation dir (Windows)

   Effect if unset:

           Mandatory

   Notes:

           No trailing "/", please.

   --------------------------------------------------------------------------

      7.2.4. actionsfile

   Specifies:

           The actions file(s) to use

   Type of value:

           Complete file name, relative to confdir

   Default values:

             standard.action     # Internal purposes, no editing recommended
             default.action      # Main actions file
             user.action         # User customizations

   Effect if unset:

           No actions are taken at all. More or less neutral proxying.

   Notes:

           Multiple actionsfile lines are permitted, and are in fact
           recommended!

           The default values include standard.action, which is used for
           internal purposes and should be loaded, default.action, which is
           the "main" actions file maintained by the developers, and
           user.action, where you can make your personal additions.

           Actions files contain all the per site and per URL configuration
           for ad blocking, cookie management, privacy considerations, etc.
           There is no point in using Privoxy without at least one actions
           file.

           Note that since Privoxy 3.0.7, the complete filename, including
           the ".action" extension has to be specified. The syntax change was
           necessary to be consistent with the other file options and to
           allow previously forbidden characters.

   --------------------------------------------------------------------------

      7.2.5. filterfile

   Specifies:

           The filter file(s) to use

   Type of value:

           File name, relative to confdir

   Default value:

           default.filter (Unix) or default.filter.txt (Windows)

   Effect if unset:

           No textual content filtering takes place, i.e. all +filter{name}
           actions in the actions files are turned neutral.

   Notes:

           Multiple filterfile lines are permitted.

           The filter files contain content modification rules that use
           regular expressions. These rules permit powerful changes on the
           content of Web pages, and optionally the headers as well, e.g.,
           you could try to disable your favorite JavaScript annoyances,
           re-write the actual displayed text, or just have some fun playing
           buzzword bingo with web pages.

           The +filter{name} actions rely on the relevant filter (name) to be
           defined in a filter file!

           A pre-defined filter file called default.filter that contains a
           number of useful filters for common problems is included in the
           distribution. See the section on the filter action for a list.

           It is recommended to place any locally adapted filters into a
           separate file, such as user.filter.

   --------------------------------------------------------------------------

      7.2.6. logfile

   Specifies:

           The log file to use

   Type of value:

           File name, relative to logdir

   Default value:

           Unset (commented out). When activated: logfile (Unix) or
           privoxy.log (Windows).

   Effect if unset:

           No logfile is written.

   Notes:

           The logfile is where all logging and error messages are written.
           The level of detail and number of messages are set with the debug
           option (see below). The logfile can be useful for tracking down a
           problem with Privoxy (e.g., it's not blocking an ad you think it
           should block) and it can help you to monitor what your browser is
           doing.

           Depending on the debug options below, the logfile may be a privacy
           risk if third parties can get access to it. As most users will
           never look at it, Privoxy 3.0.7 and later only log fatal errors by
           default.

           For most troubleshooting purposes, you will have to change that,
           please refer to the debugging section for details.

           Your logfile will grow indefinitely, and you will probably want to
           periodically remove it. On Unix systems, you can do this with a
           cron job (see "man cron"). For Red Hat based Linux distributions,
           a logrotate script has been included.

           Any log files must be writable by whatever user Privoxy is being
           run as (on Unix, default user id is "privoxy").

   --------------------------------------------------------------------------

      7.2.7. jarfile

   Specifies:

           The file to store intercepted cookies in

   Type of value:

           File name, relative to logdir

   Default value:

           Unset (commented out). When activated: jarfile (Unix) or
           privoxy.jar (Windows).

   Effect if unset:

           Intercepted cookies are not stored in a dedicated log file.

   Notes:

           The jarfile may grow to ridiculous sizes over time.

           If debug 8 (show header parsing) is enabled, cookies are also
           written to the logfile with the rest of the headers. Therefore
           this option isn't very useful and may be removed in future
           releases. Please report to the developers if you are still using
           it.

   --------------------------------------------------------------------------

      7.2.8. trustfile

   Specifies:

           The name of the trust file to use

   Type of value:

           File name, relative to confdir

   Default value:

           Unset (commented out). When activated: trust (Unix) or trust.txt
           (Windows)

   Effect if unset:

           The entire trust mechanism is disabled.

   Notes:

           The trust mechanism is an experimental feature for building
           white-lists and should be used with care. It is NOT recommended
           for the casual user.

           If you specify a trust file, Privoxy will only allow access to
           sites that are specified in the trustfile. Sites can be listed in
           one of two ways:

           Prepending a ~ character limits access to this site only (and any
           sub-paths within this site), e.g. ~www.example.com allows access
           to ~www.example.com/features/news.html, etc.

           Or, you can designate sites as trusted referrers, by prepending
           the name with a + character. The effect is that access to
           untrusted sites will be granted -- but only if a link from this
           trusted referrer was used to get there. The link target will then
           be added to the "trustfile" so that future, direct accesses will
           be granted. Sites added via this mechanism do not become trusted
           referrers themselves (i.e. they are added with a ~ designation).
           There is a limit of 512 such entries, after which new entries will
           not be made.

           If you use the + operator in the trust file, it may grow
           considerably over time.

           It is recommended that Privoxy be compiled with the
           --disable-force, --disable-toggle and --disable-editor options, if
           this feature is to be used.

           Possible applications include limiting Internet access for
           children.

   --------------------------------------------------------------------------

  7.3. Debugging

   These options are mainly useful when tracing a problem. Note that you
   might also want to invoke Privoxy with the --no-daemon command line option
   when debugging.

   --------------------------------------------------------------------------

      7.3.1. debug

   Specifies:

           Key values that determine what information gets logged.

   Type of value:

           Integer values

   Default value:

           0 (i.e.: only fatal errors (that cause Privoxy to exit) are
           logged)

   Effect if unset:

           Default value is used (see above).

   Notes:

           The available debug levels are:

  debug         1 # log each request destination (and the crunch reason if Privoxy intercepted the request)
  debug         2 # show each connection status
  debug         4 # show I/O status
  debug         8 # show header parsing
  debug        16 # log all data written to the network into the logfile
  debug        32 # debug force feature
  debug        64 # debug regular expression filters
  debug       128 # debug redirects
  debug       256 # debug GIF de-animation
  debug       512 # Common Log Format
  debug      1024 # debug kill pop-ups
  debug      2048 # CGI user interface
  debug      4096 # Startup banner and warnings.
  debug      8192 # Non-fatal errors

           To select multiple debug levels, you can either add them or use
           multiple debug lines.

           A debug level of 1 is informative because it will show you each
           request as it happens. 1, 4096 and 8192 are recommended so that
           you will notice when things go wrong. The other levels are
           probably only of interest if you are hunting down a specific
           problem. They can produce a hell of an output (especially 16).

           Privoxy used to ship with the debug levels recommended above
           enabled by default, but due to privacy concerns 3.0.7 and later
           are configured to only log fatal errors.

           If you are used to the more verbose settings, simply enable the
           debug lines below again.

           If you want to use pure CLF (Common Log Format), you should set
           "debug 512" ONLY and not enable anything else.

           Privoxy has a hard-coded limit for the length of log messages. If
           it's reached, messages are logged truncated and marked with "...
           [too long, truncated]".

           Please don't file any support requests without trying to reproduce
           the problem with increased debug level first. Once you read the
           log messages, you may even be able to solve the problem on your
           own.

   --------------------------------------------------------------------------

      7.3.2. single-threaded

   Specifies:

           Whether to run only one server thread.

   Type of value:

           None

   Default value:

           Unset

   Effect if unset:

           Multi-threaded (or, where unavailable: forked) operation, i.e. the
           ability to serve multiple requests simultaneously.

   Notes:

           This option is only there for debugging purposes. It will
           drastically reduce performance.

   --------------------------------------------------------------------------

  7.4. Access Control and Security

   This section of the config file controls the security-relevant aspects of
   Privoxy's configuration.

   --------------------------------------------------------------------------

      7.4.1. listen-address

   Specifies:

           The IP address and TCP port on which Privoxy will listen for
           client requests.

   Type of value:

           [IP-Address]:Port

   Default value:

           127.0.0.1:8118

   Effect if unset:

           Bind to 127.0.0.1 (localhost), port 8118. This is suitable and
           recommended for home users who run Privoxy on the same machine as
           their browser.

   Notes:

           You will need to configure your browser(s) to this proxy address
           and port.

           If you already have another service running on port 8118, or if
           you want to serve requests from other machines (e.g. on your local
           network) as well, you will need to override the default.

           If you leave out the IP address, Privoxy will bind to all
           interfaces (addresses) on your machine and may become reachable
           from the Internet. In that case, consider using access control
           lists (ACL's, see below), and/or a firewall.

           If you open Privoxy to untrusted users, you will also want to make
           sure that the following actions are disabled: enable-edit-actions
           and enable-remote-toggle

   Example:

           Suppose you are running Privoxy on a machine which has the address
           192.168.0.1 on your local private network (192.168.0.0) and has
           another outside connection with a different address. You want it
           to serve requests from inside only:

             listen-address  192.168.0.1:8118

   --------------------------------------------------------------------------

      7.4.2. toggle

   Specifies:

           Initial state of "toggle" status

   Type of value:

           1 or 0

   Default value:

           1

   Effect if unset:

           Act as if toggled on

   Notes:

           If set to 0, Privoxy will start in "toggled off" mode, i.e. mostly
           behave like a normal, content-neutral proxy with both ad blocking
           and content filtering disabled. See enable-remote-toggle below.

           The windows version will only display the toggle icon in the
           system tray if this option is present.

   --------------------------------------------------------------------------

      7.4.3. enable-remote-toggle

   Specifies:

           Whether or not the web-based toggle feature may be used

   Type of value:

           0 or 1

   Default value:

           0

   Effect if unset:

           The web-based toggle feature is disabled.

   Notes:

           When toggled off, Privoxy mostly acts like a normal,
           content-neutral proxy, i.e. doesn't block ads or filter content.

           Access to the toggle feature can not be controlled separately by
           "ACLs" or HTTP authentication, so that everybody who can access
           Privoxy (see "ACLs" and listen-address above) can toggle it for
           all users. So this option is not recommended for multi-user
           environments with untrusted users.

           Note that malicious client side code (e.g Java) is also capable of
           using this option.

           As a lot of Privoxy users don't read documentation, this feature
           is disabled by default.

           Note that you must have compiled Privoxy with support for this
           feature, otherwise this option has no effect.

   --------------------------------------------------------------------------

      7.4.4. enable-remote-http-toggle

   Specifies:

           Whether or not Privoxy recognizes special HTTP headers to change
           its behaviour.

   Type of value:

           0 or 1

   Default value:

           0

   Effect if unset:

           Privoxy ignores special HTTP headers.

   Notes:

           When toggled on, the client can change Privoxy's behaviour by
           setting special HTTP headers. Currently the only supported special
           header is "X-Filter: No", to disable filtering for the ongoing
           request, even if it is enabled in one of the action files.

           This feature is disabled by default. If you are using Privoxy in a
           environment with trusted clients, you may enable this feature at
           your discretion. Note that malicious client side code (e.g Java)
           is also capable of using this feature.

           This option will be removed in future releases as it has been
           obsoleted by the more general header taggers.

   --------------------------------------------------------------------------

      7.4.5. enable-edit-actions

   Specifies:

           Whether or not the web-based actions file editor may be used

   Type of value:

           0 or 1

   Default value:

           0

   Effect if unset:

           The web-based actions file editor is disabled.

   Notes:

           Access to the editor can not be controlled separately by "ACLs" or
           HTTP authentication, so that everybody who can access Privoxy (see
           "ACLs" and listen-address above) can modify its configuration for
           all users.

           This option is not recommended for environments with untrusted
           users and as a lot of Privoxy users don't read documentation, this
           feature is disabled by default.

           Note that malicious client side code (e.g Java) is also capable of
           using the actions editor and you shouldn't enable this options
           unless you understand the consequences and are sure your browser
           is configured correctly.

           Note that you must have compiled Privoxy with support for this
           feature, otherwise this option has no effect.

   --------------------------------------------------------------------------

      7.4.6. enforce-blocks

   Specifies:

           Whether the user is allowed to ignore blocks and can "go there
           anyway".

   Type of value:

           0 or 1

   Default value:

           0

   Effect if unset:

           Blocks are not enforced.

   Notes:

           Privoxy is mainly used to block and filter requests as a service
           to the user, for example to block ads and other junk that clogs
           the pipes. Privoxy's configuration isn't perfect and sometimes
           innocent pages are blocked. In this situation it makes sense to
           allow the user to enforce the request and have Privoxy ignore the
           block.

           In the default configuration Privoxy's "Blocked" page contains a
           "go there anyway" link to adds a special string (the force prefix)
           to the request URL. If that link is used, Privoxy will detect the
           force prefix, remove it again and let the request pass.

           Of course Privoxy can also be used to enforce a network policy. In
           that case the user obviously should not be able to bypass any
           blocks, and that's what the "enforce-blocks" option is for. If
           it's enabled, Privoxy hides the "go there anyway" link. If the
           user adds the force prefix by hand, it will not be accepted and
           the circumvention attempt is logged.

   Examples:

           enforce-blocks 1

   --------------------------------------------------------------------------

      7.4.7. ACLs: permit-access and deny-access

   Specifies:

           Who can access what.

   Type of value:

           src_addr[/src_masklen] [dst_addr[/dst_masklen]]

           Where src_addr and dst_addr are IP addresses in dotted decimal
           notation or valid DNS names, and src_masklen and dst_masklen are
           subnet masks in CIDR notation, i.e. integer values from 2 to 30
           representing the length (in bits) of the network address. The
           masks and the whole destination part are optional.

   Default value:

           Unset

   Effect if unset:

           Don't restrict access further than implied by listen-address

   Notes:

           Access controls are included at the request of ISPs and systems
           administrators, and are not usually needed by individual users.
           For a typical home user, it will normally suffice to ensure that
           Privoxy only listens on the localhost (127.0.0.1) or internal
           (home) network address by means of the listen-address option.

           Please see the warnings in the FAQ that Privoxy is not intended to
           be a substitute for a firewall or to encourage anyone to defer
           addressing basic security weaknesses.

           Multiple ACL lines are OK. If any ACLs are specified, Privoxy only
           talks to IP addresses that match at least one permit-access line
           and don't match any subsequent deny-access line. In other words,
           the last match wins, with the default being deny-access.

           If Privoxy is using a forwarder (see forward below) for a
           particular destination URL, the dst_addr that is examined is the
           address of the forwarder and NOT the address of the ultimate
           target. This is necessary because it may be impossible for the
           local Privoxy to determine the IP address of the ultimate target
           (that's often what gateways are used for).

           You should prefer using IP addresses over DNS names, because the
           address lookups take time. All DNS names must resolve! You can not
           use domain patterns like "*.org" or partial domain names. If a DNS
           name resolves to multiple IP addresses, only the first one is
           used.

           Denying access to particular sites by ACL may have undesired side
           effects if the site in question is hosted on a machine which also
           hosts other sites (most sites are).

   Examples:

           Explicitly define the default behavior if no ACL and
           listen-address are set: "localhost" is OK. The absence of a
           dst_addr implies that all destination addresses are OK:

             permit-access  localhost

           Allow any host on the same class C subnet as www.privoxy.org
           access to nothing but www.example.com (or other domains hosted on
           the same system):

             permit-access  www.privoxy.org/24 www.example.com/32

           Allow access from any host on the 26-bit subnet 192.168.45.64 to
           anywhere, with the exception that 192.168.45.73 may not access the
           IP address behind www.dirty-stuff.example.com:

             permit-access  192.168.45.64/26
             deny-access    192.168.45.73    www.dirty-stuff.example.com

   --------------------------------------------------------------------------

      7.4.8. buffer-limit

   Specifies:

           Maximum size of the buffer for content filtering.

   Type of value:

           Size in Kbytes

   Default value:

           4096

   Effect if unset:

           Use a 4MB (4096 KB) limit.

   Notes:

           For content filtering, i.e. the +filter and +deanimate-gif
           actions, it is necessary that Privoxy buffers the entire document
           body. This can be potentially dangerous, since a server could just
           keep sending data indefinitely and wait for your RAM to exhaust --
           with nasty consequences. Hence this option.

           When a document buffer size reaches the buffer-limit, it is
           flushed to the client unfiltered and no further attempt to filter
           the rest of the document is made. Remember that there may be
           multiple threads running, which might require up to buffer-limit
           Kbytes each, unless you have enabled "single-threaded" above.

   --------------------------------------------------------------------------

  7.5. Forwarding

   This feature allows routing of HTTP requests through a chain of multiple
   proxies.

   Forwarding can be used to chain Privoxy with a caching proxy to speed up
   browsing. Using a parent proxy may also be necessary if the machine that
   Privoxy runs on has no direct Internet access.

   Note that parent proxies can severely decrease your privacy level. For
   example a parent proxy could add your IP address to the request headers
   and if it's a caching proxy it may add the "Etag" header to revalidation
   requests again, even though you configured Privoxy to remove it. It may
   also ignore Privoxy's header time randomization and use the original
   values which could be used by the server as cookie replacement to track
   your steps between visits.

   Also specified here are SOCKS proxies. Privoxy supports the SOCKS 4 and
   SOCKS 4A protocols.

   --------------------------------------------------------------------------

      7.5.1. forward

   Specifies:

           To which parent HTTP proxy specific requests should be routed.

   Type of value:

           target_pattern http_parent[:port]

           where target_pattern is a URL pattern that specifies to which
           requests (i.e. URLs) this forward rule shall apply. Use / to
           denote "all URLs". http_parent[:port] is the DNS name or IP
           address of the parent HTTP proxy through which the requests should
           be forwarded, optionally followed by its listening port (default:
           8080). Use a single dot (.) to denote "no forwarding".

   Default value:

           Unset

   Effect if unset:

           Don't use parent HTTP proxies.

   Notes:

           If http_parent is ".", then requests are not forwarded to another
           HTTP proxy but are made directly to the web servers.

           Multiple lines are OK, they are checked in sequence, and the last
           match wins.

   Examples:

           Everything goes to an example parent proxy, except SSL on port 443
           (which it doesn't handle):

             forward   /      parent-proxy.example.org:8080
             forward   :443   .

           Everything goes to our example ISP's caching proxy, except for
           requests to that ISP's sites:

             forward   /                  caching-proxy.isp.example.net:8000
             forward   .isp.example.net   .

   --------------------------------------------------------------------------

      7.5.2. forward-socks4 and forward-socks4a

   Specifies:

           Through which SOCKS proxy (and optionally to which parent HTTP
           proxy) specific requests should be routed.

   Type of value:

           target_pattern socks_proxy[:port] http_parent[:port]

           where target_pattern is a URL pattern that specifies to which
           requests (i.e. URLs) this forward rule shall apply. Use / to
           denote "all URLs". http_parent and socks_proxy are IP addresses in
           dotted decimal notation or valid DNS names (http_parent may be "."
           to denote "no HTTP forwarding"), and the optional port parameters
           are TCP ports, i.e. integer values from 1 to 64535

   Default value:

           Unset

   Effect if unset:

           Don't use SOCKS proxies.

   Notes:

           Multiple lines are OK, they are checked in sequence, and the last
           match wins.

           The difference between forward-socks4 and forward-socks4a is that
           in the SOCKS 4A protocol, the DNS resolution of the target
           hostname happens on the SOCKS server, while in SOCKS 4 it happens
           locally.

           If http_parent is ".", then requests are not forwarded to another
           HTTP proxy but are made (HTTP-wise) directly to the web servers,
           albeit through a SOCKS proxy.

   Examples:

           From the company example.com, direct connections are made to all
           "internal" domains, but everything outbound goes through their
           ISP's proxy by way of example.com's corporate SOCKS 4A gateway to
           the Internet.

  forward-socks4a   /              socks-gw.example.com:1080  www-cache.isp.example.net:8080
  forward           .example.com   .

           A rule that uses a SOCKS 4 gateway for all destinations but no
           HTTP parent looks like this:

             forward-socks4   /               socks-gw.example.com:1080  .

           To chain Privoxy and Tor, both running on the same system, you
           would use something like:

             forward-socks4a   /               127.0.0.1:9050 .

           The public Tor network can't be used to reach your local network,
           if you need to access local servers you therefore might want to
           make some exceptions:

             forward         192.168.*.*/     .
             forward            10.*.*.*/     .
             forward           127.*.*.*/     .

           Unencrypted connections to systems in these address ranges will be
           as (un)secure as the local network is, but the alternative is that
           you can't reach the local network through Privoxy at all. Of
           course this may actually be desired and there is no reason to make
           these exceptions if you aren't sure you need them.

           If you also want to be able to reach servers in your local network
           by using their names, you will need additional exceptions that
           look like this:

            forward           localhost/     .

   --------------------------------------------------------------------------

      7.5.3. Advanced Forwarding Examples

   If you have links to multiple ISPs that provide various special content
   only to their subscribers, you can configure multiple Privoxies which have
   connections to the respective ISPs to act as forwarders to each other, so
   that your users can see the internal content of all ISPs.

   Assume that host-a has a PPP connection to isp-a.example.net. And host-b
   has a PPP connection to isp-b.example.org. Both run Privoxy. Their
   forwarding configuration can look like this:

   host-a:

     forward    /           .
     forward    .isp-b.example.net  host-b:8118

   host-b:

     forward    /           .
     forward    .isp-a.example.org  host-a:8118

   Now, your users can set their browser's proxy to use either host-a or
   host-b and be able to browse the internal content of both isp-a and isp-b.

   If you intend to chain Privoxy and squid locally, then chaining as browser
   -> squid -> privoxy is the recommended way.

   Assuming that Privoxy and squid run on the same box, your squid
   configuration could then look like this:

     # Define Privoxy as parent proxy (without ICP)
     cache_peer 127.0.0.1 parent 8118 7 no-query

     # Define ACL for protocol FTP
     acl ftp proto FTP

     # Do not forward FTP requests to Privoxy
     always_direct allow ftp

     # Forward all the rest to Privoxy
     never_direct allow all

   You would then need to change your browser's proxy settings to squid's
   address and port. Squid normally uses port 3128. If unsure consult
   http_port in squid.conf.

   You could just as well decide to only forward requests you suspect of
   leading to Windows executables through a virus-scanning parent proxy, say,
   on antivir.example.com, port 8010:

     forward   /                          .
     forward   /.*\.(exe|com|dll|zip)$    antivir.example.com:8010

   --------------------------------------------------------------------------

      7.5.4. forwarded-connect-retries

   Specifies:

           How often Privoxy retries if a forwarded connection request fails.

   Type of value:

           Number of retries.

   Default value:

           0

   Effect if unset:

           Connections forwarded through other proxies are treated like
           direct connections and no retry attempts are made.

   Notes:

           forwarded-connect-retries is mainly interesting for socks4a
           connections, where Privoxy can't detect why the connections
           failed. The connection might have failed because of a DNS timeout
           in which case a retry makes sense, but it might also have failed
           because the server doesn't exist or isn't reachable. In this case
           the retry will just delay the appearance of Privoxy's error
           message.

           Note that in the context of this option, "forwarded connections"
           includes all connections that Privoxy forwards through other
           proxies. This option is not limited to the HTTP CONNECT method.

           Only use this option, if you are getting lots of
           forwarding-related error messages that go away when you try again
           manually. Start with a small value and check Privoxy's logfile
           from time to time, to see how many retries are usually needed.

   Examples:

           forwarded-connect-retries 1

   --------------------------------------------------------------------------

      7.5.5. accept-intercepted-requests

   Specifies:

           Whether intercepted requests should be treated as valid.

   Type of value:

           0 or 1

   Default value:

           0

   Effect if unset:

           Only proxy requests are accepted, intercepted requests are treated
           as invalid.

   Notes:

           If you don't trust your clients and want to force them to use
           Privoxy, enable this option and configure your packet filter to
           redirect outgoing HTTP connections into Privoxy.

           Make sure that Privoxy's own requests aren't redirected as well.
           Additionally take care that Privoxy can't intentionally connect to
           itself, otherwise you could run into redirection loops if
           Privoxy's listening port is reachable by the outside or an
           attacker has access to the pages you visit.

   Examples:

           accept-intercepted-requests 1

   --------------------------------------------------------------------------

      7.5.6. allow-cgi-request-crunching

   Specifies:

           Whether requests to Privoxy's CGI pages can be blocked or
           redirected.

   Type of value:

           0 or 1

   Default value:

           0

   Effect if unset:

           Privoxy ignores block and redirect actions for its CGI pages.

   Notes:

           By default Privoxy ignores block or redirect actions for its CGI
           pages. Intercepting these requests can be useful in multi-user
           setups to implement fine-grained access control, but it can also
           render the complete web interface useless and make debugging
           problems painful if done without care.

           Don't enable this option unless you're sure that you really need
           it.

   Examples:

           allow-cgi-request-crunching 1

   --------------------------------------------------------------------------

      7.5.7. split-large-forms

   Specifies:

           Whether the CGI interface should stay compatible with broken HTTP
           clients.

   Type of value:

           0 or 1

   Default value:

           0

   Effect if unset:

           The CGI form generate long GET URLs.

   Notes:

           Privoxy's CGI forms can lead to rather long URLs. This isn't a
           problem as far as the HTTP standard is concerned, but it can
           confuse clients with arbitrary URL length limitations.

           Enabling split-large-forms causes Privoxy to divide big forms into
           smaller ones to keep the URL length down. It makes editing a lot
           less convenient and you can no longer submit all changes at once,
           but at least it works around this browser bug.

           If you don't notice any editing problems, there is no reason to
           enable this option, but if one of the submit buttons appears to be
           broken, you should give it a try.

   Examples:

           split-large-forms 1

   --------------------------------------------------------------------------

  7.6. Windows GUI Options

   Privoxy has a number of options specific to the Windows GUI interface:

   If "activity-animation" is set to 1, the Privoxy icon will animate when
   "Privoxy" is active. To turn off, set to 0.

     activity-animation 1


   If "log-messages" is set to 1, Privoxy will log messages to the console
   window:

     log-messages 1


   If "log-buffer-size" is set to 1, the size of the log buffer, i.e. the
   amount of memory used for the log messages displayed in the console
   window, will be limited to "log-max-lines" (see below).

   Warning: Setting this to 0 will result in the buffer to grow infinitely
   and eat up all your memory!

     log-buffer-size 1


   log-max-lines is the maximum number of lines held in the log buffer. See
   above.

     log-max-lines 200


   If "log-highlight-messages" is set to 1, Privoxy will highlight portions
   of the log messages with a bold-faced font:

     log-highlight-messages 1


   The font used in the console window:

     log-font-name Comic Sans MS


   Font size used in the console window:

     log-font-size 8


   "show-on-task-bar" controls whether or not Privoxy will appear as a button
   on the Task bar when minimized:

     show-on-task-bar 0


   If "close-button-minimizes" is set to 1, the Windows close button will
   minimize Privoxy instead of closing the program (close with the exit
   option on the File menu).

     close-button-minimizes 1


   The "hide-console" option is specific to the MS-Win console version of
   Privoxy. If this option is used, Privoxy will disconnect from and hide the
   command console.

     #hide-console


   --------------------------------------------------------------------------

8. Actions Files

   The actions files are used to define what actions Privoxy takes for which
   URLs, and thus determines how ad images, cookies and various other aspects
   of HTTP content and transactions are handled, and on which sites (or even
   parts thereof). There are a number of such actions, with a wide range of
   functionality. Each action does something a little different. These
   actions give us a veritable arsenal of tools with which to exert our
   control, preferences and independence. Actions can be combined so that
   their effects are aggregated when applied against a given set of URLs.

   There are three action files included with Privoxy with differing
   purposes:

     * default.action - is the primary action file that sets the initial
       values for all actions. It is intended to provide a base level of
       functionality for Privoxy's array of features. So it is a set of broad
       rules that should work reasonably well as-is for most users. This is
       the file that the developers are keeping updated, and making available
       to users. The user's preferences as set in standard.action, e.g.
       either Cautious (the default), Medium, or Advanced (see below).

     * user.action - is intended to be for local site preferences and
       exceptions. As an example, if your ISP or your bank has specific
       requirements, and need special handling, this kind of thing should go
       here. This file will not be upgraded.

     * standard.action - is used only by the web based editor at
       http://config.privoxy.org/edit-actions-list?f=default, to set various
       pre-defined sets of rules for the default actions section in
       default.action.

       Edit Set to Cautious Set to Medium Set to Advanced

       These have increasing levels of aggressiveness and have no influence
       on your browsing unless you select them explicitly in the editor. A
       default installation should be pre-set to Cautious (versions prior to
       3.0.5 were set to Medium). New users should try this for a while
       before adjusting the settings to more aggressive levels. The more
       aggressive the settings, then the more likelihood there is of problems
       such as sites not working as they should.

       The Edit button allows you to turn each action on/off individually for
       fine-tuning. The Cautious button changes the actions list to low/safe
       settings which will activate ad blocking and a minimal set of
       Privoxy's features, and subsequently there will be less of a chance
       for accidental problems. The Medium button sets the list to a medium
       level of other features and a low level set of privacy features. The
       Advanced button sets the list to a high level of ad blocking and
       medium level of privacy. See the chart below. The latter three buttons
       over-ride any changes via with the Edit button. More fine-tuning can
       be done in the lower sections of this internal page.

       It is not recommend to edit the standard.action file itself.

       The default profiles, and their associated actions, as pre-defined in
       standard.action are:

       Table 1. Default Configurations

       +--------------------------------------------------------------------+
       |         Feature         |  Cautious   |    Medium    |  Advanced   |
       |-------------------------+-------------+--------------+-------------|
       | Ad-blocking             | medium      | high         | high        |
       | Aggressiveness          |             |              |             |
       |-------------------------+-------------+--------------+-------------|
       | Ad-filtering by size    | no          | yes          | yes         |
       |-------------------------+-------------+--------------+-------------|
       | Ad-filtering by link    | no          | no           | yes         |
       |-------------------------+-------------+--------------+-------------|
       | Pop-up killing          | blocks only | blocks only  | blocks only |
       |-------------------------+-------------+--------------+-------------|
       | Privacy Features        | low         | medium       | medium/high |
       |-------------------------+-------------+--------------+-------------|
       | Cookie handling         | none        | session-only | kill        |
       |-------------------------+-------------+--------------+-------------|
       | Referer forging         | no          | yes          | yes         |
       |-------------------------+-------------+--------------+-------------|
       | GIF de-animation        | no          | yes          | yes         |
       |-------------------------+-------------+--------------+-------------|
       | Fast redirects          | no          | no           | yes         |
       |-------------------------+-------------+--------------+-------------|
       | HTML taming             | no          | no           | yes         |
       |-------------------------+-------------+--------------+-------------|
       | JavaScript taming       | no          | no           | yes         |
       |-------------------------+-------------+--------------+-------------|
       | Web-bug killing         | no          | yes          | yes         |
       |-------------------------+-------------+--------------+-------------|
       | Image tag reordering    | no          | no           | yes         |
       +--------------------------------------------------------------------+

   The list of actions files to be used are defined in the main configuration
   file, and are processed in the order they are defined (e.g. default.action
   is typically processed before user.action). The content of these can all
   be viewed and edited from http://config.privoxy.org/show-status. The
   over-riding principle when applying actions, is that the last action that
   matches a given URL wins. The broadest, most general rules go first
   (defined in default.action), followed by any exceptions (typically also in
   default.action), which are then followed lastly by any local preferences
   (typically in user.action). Generally, user.action has the last word.

   An actions file typically has multiple sections. If you want to use
   "aliases" in an actions file, you have to place the (optional) alias
   section at the top of that file. Then comes the default set of rules which
   will apply universally to all sites and pages (be very careful with using
   such a universal set in user.action or any other actions file after
   default.action, because it will override the result from consulting any
   previous file). And then below that, exceptions to the defined universal
   policies. You can regard user.action as an appendix to default.action,
   with the advantage that it is a separate file, which makes preserving your
   personal settings across Privoxy upgrades easier.

   Actions can be used to block anything you want, including ads, banners, or
   just some obnoxious URL whose content you would rather not see. Cookies
   can be accepted or rejected, or accepted only during the current browser
   session (i.e. not written to disk), content can be modified, some
   JavaScripts tamed, user-tracking fooled, and much more. See below for a
   complete list of actions.

   --------------------------------------------------------------------------

  8.1. Finding the Right Mix

   Note that some actions, like cookie suppression or script disabling, may
   render some sites unusable that rely on these techniques to work properly.
   Finding the right mix of actions is not always easy and certainly a matter
   of personal taste. And, things can always change, requiring refinements in
   the configuration. In general, it can be said that the more "aggressive"
   your default settings (in the top section of the actions file) are, the
   more exceptions for "trusted" sites you will have to make later. If, for
   example, you want to crunch all cookies per default, you'll have to make
   exceptions from that rule for sites that you regularly use and that
   require cookies for actually useful purposes, like maybe your bank,
   favorite shop, or newspaper.

   We have tried to provide you with reasonable rules to start from in the
   distribution actions files. But there is no general rule of thumb on these
   things. There just are too many variables, and sites are constantly
   changing. Sooner or later you will want to change the rules (and read this
   chapter again :).

   --------------------------------------------------------------------------

  8.2. How to Edit

   The easiest way to edit the actions files is with a browser by using our
   browser-based editor, which can be reached from
   http://config.privoxy.org/show-status. Note: the config file option
   enable-edit-actions must be enabled for this to work. The editor allows
   both fine-grained control over every single feature on a per-URL basis,
   and easy choosing from wholesale sets of defaults like "Cautious",
   "Medium" or "Advanced". Warning: the "Advanced" setting is more
   aggressive, and will be more likely to cause problems for some sites.
   Experienced users only!

   If you prefer plain text editing to GUIs, you can of course also directly
   edit the the actions files with your favorite text editor. Look at
   default.action which is richly commented with many good examples.

   --------------------------------------------------------------------------

  8.3. How Actions are Applied to Requests

   Actions files are divided into sections. There are special sections, like
   the "alias" sections which will be discussed later. For now let's
   concentrate on regular sections: They have a heading line (often split up
   to multiple lines for readability) which consist of a list of actions,
   separated by whitespace and enclosed in curly braces. Below that, there is
   a list of URL and tag patterns, each on a separate line.

   To determine which actions apply to a request, the URL of the request is
   compared to all URL patterns in each "action file". Every time it matches,
   the list of applicable actions for the request is incrementally updated,
   using the heading of the section in which the pattern is located. The same
   is done again for tags and tag patterns later on.

   If multiple applying sections set the same action differently, the last
   match wins. If not, the effects are aggregated. E.g. a URL might match a
   regular section with a heading line of { +handle-as-image }, then later
   another one with just { +block }, resulting in both actions to apply. And
   there may well be cases where you will want to combine actions together.
   Such a section then might look like:

     { +handle-as-image  +block }
     # Block these as if they were images. Send no block page.
      banners.example.com
      media.example.com/.*banners
      .example.com/images/ads/

   You can trace this process for URL patterns and any given URL by visiting
   http://config.privoxy.org/show-url-info.

   Examples and more detail on this is provided in the Appendix,
   Troubleshooting: Anatomy of an Action section.

   --------------------------------------------------------------------------

  8.4. Patterns

   As mentioned, Privoxy uses "patterns" to determine what actions might
   apply to which sites and pages your browser attempts to access. These
   "patterns" use wild card type pattern matching to achieve a high degree of
   flexibility. This allows one expression to be expanded and potentially
   match against many similar patterns.

   Generally, an URL pattern has the form <domain>/<path>, where both the
   <domain> and <path> are optional. (This is why the special / pattern
   matches all URLs). Note that the protocol portion of the URL pattern (e.g.
   http://) should not be included in the pattern. This is assumed already!

   The pattern matching syntax is different for the domain and path parts of
   the URL. The domain part uses a simple globbing type matching technique,
   while the path part uses a more flexible "Regular Expressions (PCRE)"
   based syntax.

   www.example.com/

           is a domain-only pattern and will match any request to
           www.example.com, regardless of which document on that server is
           requested. So ALL pages in this domain would be covered by the
           scope of this action. Note that a simple example.com is different
           and would NOT match.

   www.example.com

           means exactly the same. For domain-only patterns, the trailing /
           may be omitted.

   www.example.com/index.html$

           matches all the documents on www.example.com whose name starts
           with /index.html.

   www.example.com/index.html$

           matches only the single document /index.html on www.example.com.

   /index.html$

           matches the document /index.html, regardless of the domain, i.e.
           on any web server anywhere.

   index.html

           matches nothing, since it would be interpreted as a domain name
           and there is no top-level domain called .html. So its a mistake.

   --------------------------------------------------------------------------

    8.4.1. The Domain Pattern

   The matching of the domain part offers some flexible options: if the
   domain starts or ends with a dot, it becomes unanchored at that end. For
   example:

   .example.com

           matches any domain with first-level domain com and second-level
           domain example. For example www.example.com, example.com and
           foo.bar.baz.example.com. Note that it wouldn't match if the
           second-level domain was another-example.

   www.

           matches any domain that STARTS with www. (It also matches the
           domain www but most of the time that doesn't matter.)

   .example.

           matches any domain that CONTAINS .example.. And, by the way, also
           included would be any files or documents that exist within that
           domain since no path limitations are specified. (Correctly
           speaking: It matches any FQDN that contains example as a domain.)
           This might be www.example.com, news.example.de, or
           www.example.net/cgi/testing.pl for instance. All these cases are
           matched.

   Additionally, there are wild-cards that you can use in the domain names
   themselves. These work similarly to shell globbing type wild-cards: "*"
   represents zero or more arbitrary characters (this is equivalent to the
   "Regular Expression" based syntax of ".*"), "?" represents any single
   character (this is equivalent to the regular expression syntax of a simple
   "."), and you can define "character classes" in square brackets which is
   similar to the same regular expression technique. All of this can be
   freely mixed:

   ad*.example.com

           matches "adserver.example.com", "ads.example.com", etc but not
           "sfads.example.com"

   *ad*.example.com

           matches all of the above, and then some.

   .?pix.com

           matches www.ipix.com, pictures.epix.com, a.b.c.d.e.upix.com etc.

   www[1-9a-ez].example.c*

           matches www1.example.com, www4.example.cc, wwwd.example.cy,
           wwwz.example.com etc., but not wwww.example.com.

   While flexible, this is not the sophistication of full regular expression
   based syntax.

   --------------------------------------------------------------------------

    8.4.2. The Path Pattern

   Privoxy uses Perl compatible (PCRE) "Regular Expression" based syntax
   (through the PCRE library) for matching the path portion (after the
   slash), and is thus more flexible.

   There is an Appendix with a brief quick-start into regular expressions,
   and full (very technical) documentation on PCRE regex syntax is available
   on-line at http://www.pcre.org/man.txt. You might also find the Perl man
   page on regular expressions (man perlre) useful, which is available
   on-line at http://perldoc.perl.org/perlre.html.

   Note that the path pattern is automatically left-anchored at the "/", i.e.
   it matches as if it would start with a "^" (regular expression speak for
   the beginning of a line).

   Please also note that matching in the path is CASE INSENSITIVE by default,
   but you can switch to case sensitive at any point in the pattern by using
   the "(?-i)" switch: www.example.com/(?-i)PaTtErN.* will match only
   documents whose path starts with PaTtErN in exactly this capitalization.

   .example.com/.*

           Is equivalent to just ".example.com", since any documents within
           that domain are matched with or without the ".*" regular
           expression. This is redundant

   .example.com/.*/index.html$

           Will match any page in the domain of "example.com" that is named
           "index.html", and that is part of some path. For example, it
           matches "www.example.com/testing/index.html" but NOT
           "www.example.com/index.html" because the regular expression called
           for at least two "/'s", thus the path requirement. It also would
           match "www.example.com/testing/index_html", because of the special
           meta-character ".".

   .example.com/(.*/)?index\.html$

           This regular expression is conditional so it will match any page
           named "index.html" regardless of path which in this case can have
           one or more "/'s". And this one must contain exactly ".html" (but
           does not have to end with that!).

   .example.com/(.*/)(ads|banners?|junk)

           This regular expression will match any path of "example.com" that
           contains any of the words "ads", "banner", "banners" (because of
           the "?") or "junk". The path does not have to end in these words,
           just contain them.

   .example.com/(.*/)(ads|banners?|junk)/.*\.(jpe?g|gif|png)$

           This is very much the same as above, except now it must end in
           either ".jpg", ".jpeg", ".gif" or ".png". So this one is limited
           to common image formats.

   There are many, many good examples to be found in default.action, and more
   tutorials below in Appendix on regular expressions.

   --------------------------------------------------------------------------

    8.4.3. The Tag Pattern

   Tag patterns are used to change the applying actions based on the
   request's tags. Tags can be created with either the client-header-tagger
   or the server-header-tagger action.

   Tag patterns have to start with "TAG:", so Privoxy can tell them apart
   from URL patterns. Everything after the colon including white space, is
   interpreted as a regular expression with path pattern syntax, except that
   tag patterns aren't left-anchored automatically (Privoxy doesn't silently
   add a "^", you have to do it yourself if you need it).

   To match all requests that are tagged with "foo" your pattern line should
   be "TAG:^foo$", "TAG:foo" would work as well, but it would also match
   requests whose tags contain "foo" somewhere. "TAG: foo" wouldn't work as
   it requires white space.

   Sections can contain URL and tag patterns at the same time, but tag
   patterns are checked after the URL patterns and thus always overrule them,
   even if they are located before the URL patterns.

   Once a new tag is added, Privoxy checks right away if it's matched by one
   of the tag patterns and updates the action settings accordingly. As a
   result tags can be used to activate other tagger actions, as long as these
   other taggers look for headers that haven't already be parsed.

   For example you could tag client requests which use the POST method, then
   use this tag to activate another tagger that adds a tag if cookies are
   sent, and then use a block action based on the cookie tag. This allows the
   outcome of one action, to be input into a subsequent action. However if
   you'd reverse the position of the described taggers, and activated the
   method tagger based on the cookie tagger, no method tags would be created.
   The method tagger would look for the request line, but at the time the
   cookie tag is created, the request line has already been parsed.

   While this is a limitation you should be aware of, this kind of
   indirection is seldom needed anyway and even the example doesn't make too
   much sense.

   --------------------------------------------------------------------------

  8.5. Actions

   All actions are disabled by default, until they are explicitly enabled
   somewhere in an actions file. Actions are turned on if preceded with a
   "+", and turned off if preceded with a "-". So a +action means "do that
   action", e.g. +block means "please block URLs that match the following
   patterns", and -block means "don't block URLs that match the following
   patterns, even if +block previously applied."

   Again, actions are invoked by placing them on a line, enclosed in curly
   braces and separated by whitespace, like in {+some-action
   -some-other-action{some-parameter}}, followed by a list of URL patterns,
   one per line, to which they apply. Together, the actions line and the
   following pattern lines make up a section of the actions file.

   Actions fall into three categories:

     * Boolean, i.e the action can only be "enabled" or "disabled". Syntax:

         +name        # enable action name
         -name        # disable action name

       Example: +block

     * Parameterized, where some value is required in order to enable this
       type of action. Syntax:

         +name{param}  # enable action and set parameter to param,
                      # overwriting parameter from previous match if necessary
         -name         # disable action. The parameter can be omitted

       Note that if the URL matches multiple positive forms of a
       parameterized action, the last match wins, i.e. the params from
       earlier matches are simply ignored.

       Example: +hide-user-agent{Mozilla/5.0 (X11; U; FreeBSD i386; en-US;
       rv:1.8.1.4) Gecko/20070602 Firefox/2.0.0.4}

     * Multi-value. These look exactly like parameterized actions, but they
       behave differently: If the action applies multiple times to the same
       URL, but with different parameters, all the parameters from all
       matches are remembered. This is used for actions that can be executed
       for the same request repeatedly, like adding multiple headers, or
       filtering through multiple filters. Syntax:

  +name{param}   # enable action and add param to the list of parameters
  -name{param}   # remove the parameter param from the list of parameters
                # If it was the last one left, disable the action.
  -name          # disable this action completely and remove all parameters from the list

       Examples: +add-header{X-Fun-Header: Some text} and
       +filter{html-annoyances}

   If nothing is specified in any actions file, no "actions" are taken. So in
   this case Privoxy would just be a normal, non-blocking, non-filtering
   proxy. You must specifically enable the privacy and blocking features you
   need (although the provided default actions files will give a good
   starting point).

   Later defined action sections always over-ride earlier ones of the same
   type. So exceptions to any rules you make, should come in the latter part
   of the file (or in a file that is processed later when using multiple
   actions files such as user.action). For multi-valued actions, the actions
   are applied in the order they are specified. Actions files are processed
   in the order they are defined in config (the default installation has
   three actions files). It also quite possible for any given URL to match
   more than one "pattern" (because of wildcards and regular expressions),
   and thus to trigger more than one set of actions! Last match wins.

   The list of valid Privoxy actions are:

   --------------------------------------------------------------------------

      8.5.1. add-header

   Typical use:

           Confuse log analysis, custom applications

   Effect:

           Sends a user defined HTTP header to the web server.

   Type:

           Multi-value.

   Parameter:

           Any string value is possible. Validity of the defined HTTP headers
           is not checked. It is recommended that you use the "X-" prefix for
           custom headers.

   Notes:

           This action may be specified multiple times, in order to define
           multiple headers. This is rarely needed for the typical user. If
           you don't know what "HTTP headers" are, you definitely don't need
           to worry about this one.

   Example usage:

           +add-header{X-User-Tracking: sucks}

   --------------------------------------------------------------------------

      8.5.2. block

   Typical use:

           Block ads or other unwanted content

   Effect:

           Requests for URLs to which this action applies are blocked, i.e.
           the requests are trapped by Privoxy and the requested URL is never
           retrieved, but is answered locally with a substitute page or
           image, as determined by the handle-as-image, set-image-blocker,
           and handle-as-empty-document actions.

   Type:

           Boolean.

   Parameter:

           N/A

   Notes:

           Privoxy sends a special "BLOCKED" page for requests to blocked
           pages. This page contains links to find out why the request was
           blocked, and a click-through to the blocked content (the latter
           only if compiled with the force feature enabled). The "BLOCKED"
           page adapts to the available screen space -- it displays
           full-blown if space allows, or miniaturized and text-only if
           loaded into a small frame or window. If you are using Privoxy
           right now, you can take a look at the "BLOCKED" page.

           A very important exception occurs if both block and
           handle-as-image, apply to the same request: it will then be
           replaced by an image. If set-image-blocker (see below) also
           applies, the type of image will be determined by its parameter, if
           not, the standard checkerboard pattern is sent.

           It is important to understand this process, in order to understand
           how Privoxy deals with ads and other unwanted content. Blocking is
           a core feature, and one upon which various other features depend.

           The filter action can perform a very similar task, by "blocking"
           banner images and other content through rewriting the relevant
           URLs in the document's HTML source, so they don't get requested in
           the first place. Note that this is a totally different technique,
           and it's easy to confuse the two.

   Example usage (section):

           {+block}
           # Block and replace with "blocked" page
            .nasty-stuff.example.com

           {+block +handle-as-image}
           # Block and replace with image
            .ad.doubleclick.net
            .ads.r.us/banners/

           {+block +handle-as-empty-document}
           # Block and then ignore
            adserver.exampleclick.net/.*\.js$

   --------------------------------------------------------------------------

      8.5.3. client-header-filter

   Typical use:

           Rewrite or remove single client headers.

   Effect:

           All client headers to which this action applies are filtered
           on-the-fly through the specified regular expression based
           substitutions.

   Type:

           Parameterized.

   Parameter:

           The name of a client-header filter, as defined in one of the
           filter files.

   Notes:

           Client-header filters are applied to each header on its own, not
           to all at once. This makes it easier to diagnose problems, but on
           the downside you can't write filters that only change header x if
           header y's value is z. You can do that by using tags though.

           Client-header filters are executed after the other header actions
           have finished and use their output as input.

           If the request URL gets changed, Privoxy will detect that and use
           the new one. This can be used to rewrite the request destination
           behind the client's back, for example to specify a Tor exit relay
           for certain requests.

           Please refer to the filter file chapter to learn which
           client-header filters are available by default, and how to create
           your own.

   Example usage (section):

           {+client-header-filter{hide-tor-exit-notation}}
           .exit/


   --------------------------------------------------------------------------

      8.5.4. client-header-tagger

   Typical use:

           Block requests based on their headers.

   Effect:

           Client headers to which this action applies are filtered
           on-the-fly through the specified regular expression based
           substitutions, the result is used as tag.

   Type:

           Parameterized.

   Parameter:

           The name of a client-header tagger, as defined in one of the
           filter files.

   Notes:

           Client-header taggers are applied to each header on its own, and
           as the header isn't modified, each tagger "sees" the original.

           Client-header taggers are the first actions that are executed and
           their tags can be used to control every other action.

   Example usage (section):

           # Tag every request with the User-Agent header
           {+client-header-tagger{user-agent}}
           /


   --------------------------------------------------------------------------

      8.5.5. content-type-overwrite

   Typical use:

           Stop useless download menus from popping up, or change the
           browser's rendering mode

   Effect:

           Replaces the "Content-Type:" HTTP server header.

   Type:

           Parameterized.

   Parameter:

           Any string.

   Notes:

           The "Content-Type:" HTTP server header is used by the browser to
           decide what to do with the document. The value of this header can
           cause the browser to open a download menu instead of displaying
           the document by itself, even if the document's format is supported
           by the browser.

           The declared content type can also affect which rendering mode the
           browser chooses. If XHTML is delivered as "text/html", many
           browsers treat it as yet another broken HTML document. If it is
           send as "application/xml", browsers with XHTML support will only
           display it, if the syntax is correct.

           If you see a web site that proudly uses XHTML buttons, but sets
           "Content-Type: text/html", you can use Privoxy to overwrite it
           with "application/xml" and validate the web master's claim inside
           your XHTML-supporting browser. If the syntax is incorrect, the
           browser will complain loudly.

           You can also go the opposite direction: if your browser prints
           error messages instead of rendering a document falsely declared as
           XHTML, you can overwrite the content type with "text/html" and
           have it rendered as broken HTML document.

           By default content-type-overwrite only replaces "Content-Type:"
           headers that look like some kind of text. If you want to overwrite
           it unconditionally, you have to combine it with force-text-mode.
           This limitation exists for a reason, think twice before
           circumventing it.

           Most of the time it's easier to replace this action with a custom
           server-header filter. It allows you to activate it for every
           document of a certain site and it will still only replace the
           content types you aimed at.

           Of course you can apply content-type-overwrite to a whole site and
           then make URL based exceptions, but it's a lot more work to get
           the same precision.

   Example usage (sections):

     # Check if www.example.net/ really uses valid XHTML
     { +content-type-overwrite{application/xml} }
     www.example.net/

     # but leave the content type unmodified if the URL looks like a style sheet
     {-content-type-overwrite}
     www.example.net/.*\.css$
     www.example.net/.*style

   --------------------------------------------------------------------------

      8.5.6. crunch-client-header

   Typical use:

           Remove a client header Privoxy has no dedicated action for.

   Effect:

           Deletes every header sent by the client that contains the string
           the user supplied as parameter.

   Type:

           Parameterized.

   Parameter:

           Any string.

   Notes:

           This action allows you to block client headers for which no
           dedicated Privoxy action exists. Privoxy will remove every client
           header that contains the string you supplied as parameter.

           Regular expressions are not supported and you can't use this
           action to block different headers in the same request, unless they
           contain the same string.

           crunch-client-header is only meant for quick tests. If you have to
           block several different headers, or only want to modify parts of
           them, you should use a client-header filter.

           +---------------------------------------------------------+
           |                         Warning                         |
           |---------------------------------------------------------|
           | Don't block any header without understanding the        |
           | consequences.                                           |
           +---------------------------------------------------------+

   Example usage (section):

           # Block the non-existent "Privacy-Violation:" client header
           { +crunch-client-header{Privacy-Violation:} }
           /


   --------------------------------------------------------------------------

      8.5.7. crunch-if-none-match

   Typical use:

           Prevent yet another way to track the user's steps between
           sessions.

   Effect:

           Deletes the "If-None-Match:" HTTP client header.

   Type:

           Boolean.

   Parameter:

           N/A

   Notes:

           Removing the "If-None-Match:" HTTP client header is useful for
           filter testing, where you want to force a real reload instead of
           getting status code "304" which would cause the browser to use a
           cached copy of the page.

           It is also useful to make sure the header isn't used as a cookie
           replacement (unlikely but possible).

           Blocking the "If-None-Match:" header shouldn't cause any caching
           problems, as long as the "If-Modified-Since:" header isn't blocked
           or missing as well.

           It is recommended to use this action together with
           hide-if-modified-since and overwrite-last-modified.

   Example usage (section):

           # Let the browser revalidate cached documents but don't
           # allow the server to use the revalidation headers for user tracking.
           {+hide-if-modified-since{-60} \
            +overwrite-last-modified{randomize} \
            +crunch-if-none-match}
           /

   --------------------------------------------------------------------------

      8.5.8. crunch-incoming-cookies

   Typical use:

           Prevent the web server from setting HTTP cookies on your system

   Effect:

           Deletes any "Set-Cookie:" HTTP headers from server replies.

   Type:

           Boolean.

   Parameter:

           N/A

   Notes:

           This action is only concerned with incoming HTTP cookies. For
           outgoing HTTP cookies, use crunch-outgoing-cookies. Use both to
           disable HTTP cookies completely.

           It makes no sense at all to use this action in conjunction with
           the session-cookies-only action, since it would prevent the
           session cookies from being set. See also filter-content-cookies.

   Example usage:

           +crunch-incoming-cookies

   --------------------------------------------------------------------------

      8.5.9. crunch-server-header

   Typical use:

           Remove a server header Privoxy has no dedicated action for.

   Effect:

           Deletes every header sent by the server that contains the string
           the user supplied as parameter.

   Type:

           Parameterized.

   Parameter:

           Any string.

   Notes:

           This action allows you to block server headers for which no
           dedicated Privoxy action exists. Privoxy will remove every server
           header that contains the string you supplied as parameter.

           Regular expressions are not supported and you can't use this
           action to block different headers in the same request, unless they
           contain the same string.

           crunch-server-header is only meant for quick tests. If you have to
           block several different headers, or only want to modify parts of
           them, you should use a custom server-header filter.

           +---------------------------------------------------------+
           |                         Warning                         |
           |---------------------------------------------------------|
           | Don't block any header without understanding the        |
           | consequences.                                           |
           +---------------------------------------------------------+

   Example usage (section):

           # Crunch server headers that try to prevent caching
           { +crunch-server-header{no-cache} }
           /

   --------------------------------------------------------------------------

      8.5.10. crunch-outgoing-cookies

   Typical use:

           Prevent the web server from reading any HTTP cookies from your
           system

   Effect:

           Deletes any "Cookie:" HTTP headers from client requests.

   Type:

           Boolean.

   Parameter:

           N/A

   Notes:

           This action is only concerned with outgoing HTTP cookies. For
           incoming HTTP cookies, use crunch-incoming-cookies. Use both to
           disable HTTP cookies completely.

           It makes no sense at all to use this action in conjunction with
           the session-cookies-only action, since it would prevent the
           session cookies from being read.

   Example usage:

           +crunch-outgoing-cookies

   --------------------------------------------------------------------------

      8.5.11. deanimate-gifs

   Typical use:

           Stop those annoying, distracting animated GIF images.

   Effect:

           De-animate GIF animations, i.e. reduce them to their first or last
           image.

   Type:

           Parameterized.

   Parameter:

           "last" or "first"

   Notes:

           This will also shrink the images considerably (in bytes, not
           pixels!). If the option "first" is given, the first frame of the
           animation is used as the replacement. If "last" is given, the last
           frame of the animation is used instead, which probably makes more
           sense for most banner animations, but also has the risk of not
           showing the entire last frame (if it is only a delta to an earlier
           frame).

           You can safely use this action with patterns that will also match
           non-GIF objects, because no attempt will be made at anything that
           doesn't look like a GIF.

   Example usage:

           +deanimate-gifs{last}

   --------------------------------------------------------------------------

      8.5.12. downgrade-http-version

   Typical use:

           Work around (very rare) problems with HTTP/1.1

   Effect:

           Downgrades HTTP/1.1 client requests and server replies to
           HTTP/1.0.

   Type:

           Boolean.

   Parameter:

           N/A

   Notes:

           This is a left-over from the time when Privoxy didn't support
           important HTTP/1.1 features well. It is left here for the unlikely
           case that you experience HTTP/1.1 related problems with some
           server out there. Not all HTTP/1.1 features and requirements are
           supported yet, so there is a chance you might need this action.

   Example usage (section):

           {+downgrade-http-version}
           problem-host.example.com

   --------------------------------------------------------------------------

      8.5.13. fast-redirects

   Typical use:

           Fool some click-tracking scripts and speed up indirect links.

   Effect:

           Detects redirection URLs and redirects the browser without
           contacting the redirection server first.

   Type:

           Parameterized.

   Parameter:

              * "simple-check" to just search for the string "http://" to
                detect redirection URLs.

              * "check-decoded-url" to decode URLs (if necessary) before
                searching for redirection URLs.

   Notes:

           Many sites, like yahoo.com, don't just link to other sites.
           Instead, they will link to some script on their own servers,
           giving the destination as a parameter, which will then redirect
           you to the final target. URLs resulting from this scheme typically
           look like:
           "http://www.example.org/click-tracker.cgi?target=http%3a//www.example.net/".

           Sometimes, there are even multiple consecutive redirects encoded
           in the URL. These redirections via scripts make your web browsing
           more traceable, since the server from which you follow such a link
           can see where you go to. Apart from that, valuable bandwidth and
           time is wasted, while your browser asks the server for one
           redirect after the other. Plus, it feeds the advertisers.

           This feature is currently not very smart and is scheduled for
           improvement. If it is enabled by default, you will have to create
           some exceptions to this action. It can lead to failures in several
           ways:

           Not every URLs with other URLs as parameters is evil. Some sites
           offer a real service that requires this information to work. For
           example a validation service needs to know, which document to
           validate. fast-redirects assumes that every URL parameter that
           looks like another URL is a redirection target, and will always
           redirect to the last one. Most of the time the assumption is
           correct, but if it isn't, the user gets redirected anyway.

           Another failure occurs if the URL contains other parameters after
           the URL parameter. The URL:
           "http://www.example.org/?redirect=http%3a//www.example.net/&foo=bar".
           contains the redirection URL "http://www.example.net/", followed
           by another parameter. fast-redirects doesn't know that and will
           cause a redirect to "http://www.example.net/&foo=bar". Depending
           on the target server configuration, the parameter will be silently
           ignored or lead to a "page not found" error. You can prevent this
           problem by first using the redirect action to remove the last part
           of the URL, but it requires a little effort.

           To detect a redirection URL, fast-redirects only looks for the
           string "http://", either in plain text (invalid but often used) or
           encoded as "http%3a//". Some sites use their own URL encoding
           scheme, encrypt the address of the target server or replace it
           with a database id. In theses cases fast-redirects is fooled and
           the request reaches the redirection server where it probably gets
           logged.

   Example usage:

            { +fast-redirects{simple-check} }
              one.example.com

            { +fast-redirects{check-decoded-url} }
              another.example.com/testing

   --------------------------------------------------------------------------

      8.5.14. filter

   Typical use:

           Get rid of HTML and JavaScript annoyances, banner advertisements
           (by size), do fun text replacements, add personalized effects,
           etc.

   Effect:

           All instances of text-based type, most notably HTML and
           JavaScript, to which this action applies, can be filtered
           on-the-fly through the specified regular expression based
           substitutions. (Note: as of version 3.0.3 plain text documents are
           exempted from filtering, because web servers often use the
           text/plain MIME type for all files whose type they don't know.)

   Type:

           Parameterized.

   Parameter:

           The name of a content filter, as defined in the filter file.
           Filters can be defined in one or more files as defined by the
           filterfile option in the config file. default.filter is the
           collection of filters supplied by the developers. Locally defined
           filters should go in their own file, such as user.filter.

           When used in its negative form, and without parameters, all
           filtering is completely disabled.

   Notes:

           For your convenience, there are a number of pre-defined filters
           available in the distribution filter file that you can use. See
           the examples below for a list.

           Filtering requires buffering the page content, which may appear to
           slow down page rendering since nothing is displayed until all
           content has passed the filters. (It does not really take longer,
           but seems that way since the page is not incrementally displayed.)
           This effect will be more noticeable on slower connections.

           "Rolling your own" filters requires a knowledge of "Regular
           Expressions" and "HTML". This is very powerful feature, and
           potentially very intrusive. Filters should be used with caution,
           and where an equivalent "action" is not available.

           The amount of data that can be filtered is limited to the
           buffer-limit option in the main config file. The default is 4096
           KB (4 Megs). Once this limit is exceeded, the buffered data, and
           all pending data, is passed through unfiltered.

           Inappropriate MIME types, such as zipped files, are not filtered
           at all. (Again, only text-based types except plain text).
           Encrypted SSL data (from HTTPS servers) cannot be filtered either,
           since this would violate the integrity of the secure transaction.
           In some situations it might be necessary to protect certain text,
           like source code, from filtering by defining appropriate -filter
           exceptions.

           Compressed content can't be filtered either, unless Privoxy is
           compiled with zlib support (requires at least Privoxy 3.0.7), in
           which case Privoxy will decompress the content before filtering
           it.

           If you use a Privoxy version without zlib support, but want
           filtering to work on as much documents as possible, even those
           that would normally be sent compressed, you must use the
           prevent-compression action in conjunction with filter.

           Content filtering can achieve some of the same effects as the
           block action, i.e. it can be used to block ads and banners. But
           the mechanism works quite differently. One effective use, is to
           block ad banners based on their size (see below), since many of
           these seem to be somewhat standardized.

           Feedback with suggestions for new or improved filters is
           particularly welcome!

           The below list has only the names and a one-line description of
           each predefined filter. There are more verbose explanations of
           what these filters do in the filter file chapter.

   Example usage (with filters from the distribution default.filter file).
   See the Predefined Filters section for more explanation on each:

+filter{js-annoyances}       # Get rid of particularly annoying JavaScript abuse

+filter{js-events}           # Kill all JS event bindings (Radically destructive! Only for extra nasty sites)

      +filter{html-annoyances}     # Get rid of particularly annoying HTML abuse

 +filter{content-cookies}     # Kill cookies that come in the HTML or JS content

+filter{refresh-tags}        # Kill automatic refresh tags (for dial-on-demand setups)

+filter{unsolicited-popups}  # Disable only unsolicited pop-up windows. Useful if your browser lacks this ability.

+filter{all-popups}          # Kill all popups in JavaScript and HTML. Useful if your browser lacks this ability.

+filter{img-reorder}         # Reorder attributes in <img> tags to make the banners-by-* filters more effective

           +filter{banners-by-size}     # Kill banners by size

+filter{banners-by-link}     # Kill banners by their links to known clicktrackers

+filter{webbugs}             # Squish WebBugs (1x1 invisible GIFs used for user tracking)

+filter{tiny-textforms}      # Extend those tiny textareas up to 40x80 and kill the hard wrap

+filter{jumping-windows}     # Prevent windows from resizing and moving themselves

    +filter{frameset-borders}    # Give frames a border and make them resizeable

   +filter{demoronizer}         # Fix MS's non-standard use of standard charsets

           +filter{shockwave-flash}     # Kill embedded Shockwave Flash objects

           +filter{quicktime-kioskmode} # Make Quicktime movies savable

   +filter{fun}                 # Text replacements for subversive browsing fun!

           +filter{crude-parental}      # Crude parental filtering (demo only)

   +filter{ie-exploits}         # Disable a known Internet Explorer bug exploits

+filter{site-specifics}      # Custom filters for specific site related problems

+filter{google}              # Removes text ads and other Google specific improvements

+filter{yahoo}               # Removes text ads and other Yahoo specific improvements

+filter{msn}                 # Removes text ads and other MSN specific improvements

           +filter{blogspot}            # Cleans up Blogspot blogs

+filter{no-ping}             # Removes non-standard ping attributes from anchor and area tags

   --------------------------------------------------------------------------

      8.5.15. force-text-mode

   Typical use:

           Force Privoxy to treat a document as if it was in some kind of
           text format.

   Effect:

           Declares a document as text, even if the "Content-Type:" isn't
           detected as such.

   Type:

           Boolean.

   Parameter:

           N/A

   Notes:

           As explained above, Privoxy tries to only filter files that are in
           some kind of text format. The same restrictions apply to
           content-type-overwrite. force-text-mode declares a document as
           text, without looking at the "Content-Type:" first.

           +---------------------------------------------------------+
           |                         Warning                         |
           |---------------------------------------------------------|
           | Think twice before activating this action. Filtering    |
           | binary data with regular expressions can cause file     |
           | damage.                                                 |
           +---------------------------------------------------------+

   Example usage:

           +force-text-mode


   --------------------------------------------------------------------------

      8.5.16. forward-override

   Typical use:

           Change the forwarding settings based on User-Agent or request
           origin

   Effect:

           Overrules the forward directives in the configuration file.

   Type:

           Multi-value.

   Parameter:

              * "forward ." to use a direct connection without any additional
                proxies.

              * "forward 127.0.0.1:8123" to use the HTTP proxy listening at
                127.0.0.1 port 8123.

              * "forward-socks4a 127.0.0.1:9050 ." to use the socks4a proxy
                listening at 127.0.0.1 port 9050. Replace "forward-socks4a"
                with "forward-socks4" to use a socks4 connection (with local
                DNS resolution) instead.

              * "forward-socks4a 127.0.0.1:9050 proxy.example.org:8000" to
                use the socks4a proxy listening at 127.0.0.1 port 9050 to
                reach the HTTP proxy listening at proxy.example.org port
                8000. Replace "forward-socks4a" with "forward-socks4" to use
                a socks4 connection (with local DNS resolution) instead.

   Notes:

           This action takes parameters similar to the forward directives in
           the configuration file, but without the URL pattern. It can be
           used as replacement, but normally it's only used in cases where
           matching based on the request URL isn't sufficient.

           +---------------------------------------------------------+
           |                         Warning                         |
           |---------------------------------------------------------|
           | Please read the description for the forward directives  |
           | before using this action. Forwarding to the wrong       |
           | people will reduce your privacy and increase the        |
           | chances of man-in-the-middle attacks.                   |
           |                                                         |
           | If the ports are missing or invalid, default values     |
           | will be used. This might change in the future and you   |
           | shouldn't rely on it. Otherwise incorrect syntax causes |
           | Privoxy to exit.                                        |
           |                                                         |
           | Use the show-url-info CGI page to verify that your      |
           | forward settings do what you thought the do.            |
           +---------------------------------------------------------+

   Example usage:

           # Always use direct connections for requests previously tagged as
           # "User-Agent: fetch libfetch/2.0" and make sure
           # resuming downloads continues to work.
           # This way you can continue to use Tor for your normal browsing,
           # without overloading the Tor network with your FreeBSD ports updates
           # or downloads of bigger files like ISOs.
           # Note that HTTP headers are easy to fake and therefore their
           # values are as (un)trustworthy as your clients and users.
           {+forward-override{forward .} \
            -hide-if-modified-since      \
            -overwrite-last-modified     \
           }
           TAG:^User-Agent: fetch libfetch/2\.0$


   --------------------------------------------------------------------------

      8.5.17. handle-as-empty-document

   Typical use:

           Mark URLs that should be replaced by empty documents if they get
           blocked

   Effect:

           This action alone doesn't do anything noticeable. It just marks
           URLs. If the block action also applies, the presence or absence of
           this mark decides whether an HTML "BLOCKED" page, or an empty
           document will be sent to the client as a substitute for the
           blocked content. The empty document isn't literally empty, but
           actually contains a single space.

   Type:

           Boolean.

   Parameter:

           N/A

   Notes:

           Some browsers complain about syntax errors if JavaScript documents
           are blocked with Privoxy's default HTML page; this option can be
           used to silence them. And of course this action can also be used
           to eliminate the Privoxy BLOCKED message in frames.

           The content type for the empty document can be specified with
           content-type-overwrite{}, but usually this isn't necessary.

   Example usage:

           # Block all documents on example.org that end with ".js",
           # but send an empty document instead of the usual HTML message.
           {+block +handle-as-empty-document}
           example.org/.*\.js$


   --------------------------------------------------------------------------

      8.5.18. handle-as-image

   Typical use:

           Mark URLs as belonging to images (so they'll be replaced by images
           if they do get blocked, rather than HTML pages)

   Effect:

           This action alone doesn't do anything noticeable. It just marks
           URLs as images. If the block action also applies, the presence or
           absence of this mark decides whether an HTML "blocked" page, or a
           replacement image (as determined by the set-image-blocker action)
           will be sent to the client as a substitute for the blocked
           content.

   Type:

           Boolean.

   Parameter:

           N/A

   Notes:

           The below generic example section is actually part of
           default.action. It marks all URLs with well-known image file name
           extensions as images and should be left intact.

           Users will probably only want to use the handle-as-image action in
           conjunction with block, to block sources of banners, whose URLs
           don't reflect the file type, like in the second example section.

           Note that you cannot treat HTML pages as images in most cases. For
           instance, (in-line) ad frames require an HTML page to be sent, or
           they won't display properly. Forcing handle-as-image in this
           situation will not replace the ad frame with an image, but lead to
           error messages.

   Example usage (sections):

           # Generic image extensions:
           #
           {+handle-as-image}
           /.*\.(gif|jpg|jpeg|png|bmp|ico)$

           # These don't look like images, but they're banners and should be
           # blocked as images:
           #
           {+block +handle-as-image}
           some.nasty-banner-server.com/junk.cgi\?output=trash

           # Banner source! Who cares if they also have non-image content?
           ad.doubleclick.net

   --------------------------------------------------------------------------

      8.5.19. hide-accept-language

   Typical use:

           Pretend to use different language settings.

   Effect:

           Deletes or replaces the "Accept-Language:" HTTP header in client
           requests.

   Type:

           Parameterized.

   Parameter:

           Keyword: "block", or any user defined value.

   Notes:

           Faking the browser's language settings can be useful to make a
           foreign User-Agent set with hide-user-agent more believable.

           However some sites with content in different languages check the
           "Accept-Language:" to decide which one to take by default.
           Sometimes it isn't possible to later switch to another language
           without changing the "Accept-Language:" header first.

           Therefore it's a good idea to either only change the
           "Accept-Language:" header to languages you understand, or to
           languages that aren't wide spread.

           Before setting the "Accept-Language:" header to a rare language,
           you should consider that it helps to make your requests unique and
           thus easier to trace. If you don't plan to change this header
           frequently, you should stick to a common language.

   Example usage (section):

# Pretend to use Canadian language settings.
{+hide-accept-language{en-ca} \
+hide-user-agent{Mozilla/5.0 (X11; U; OpenBSD i386; en-CA; rv:1.8.0.4) Gecko/20060628 Firefox/1.5.0.4} \
}
/

   --------------------------------------------------------------------------

      8.5.20. hide-content-disposition

   Typical use:

           Prevent download menus for content you prefer to view inside the
           browser.

   Effect:

           Deletes or replaces the "Content-Disposition:" HTTP header set by
           some servers.

   Type:

           Parameterized.

   Parameter:

           Keyword: "block", or any user defined value.

   Notes:

           Some servers set the "Content-Disposition:" HTTP header for
           documents they assume you want to save locally before viewing
           them. The "Content-Disposition:" header contains the file name the
           browser is supposed to use by default.

           In most browsers that understand this header, it makes it
           impossible to just view the document, without downloading it
           first, even if it's just a simple text file or an image.

           Removing the "Content-Disposition:" header helps to prevent this
           annoyance, but some browsers additionally check the
           "Content-Type:" header, before they decide if they can display a
           document without saving it first. In these cases, you have to
           change this header as well, before the browser stops displaying
           download menus.

           It is also possible to change the server's file name suggestion to
           another one, but in most cases it isn't worth the time to set it
           up.

           This action will probably be removed in the future, use
           server-header filters instead.

   Example usage:

           # Disarm the download link in Sourceforge's patch tracker
           { -filter \
            +content-type-overwrite{text/plain}\
            +hide-content-disposition{block} }
            .sourceforge.net/tracker/download\.php

   --------------------------------------------------------------------------

      8.5.21. hide-if-modified-since

   Typical use:

           Prevent yet another way to track the user's steps between
           sessions.

   Effect:

           Deletes the "If-Modified-Since:" HTTP client header or modifies
           its value.

   Type:

           Parameterized.

   Parameter:

           Keyword: "block", or a user defined value that specifies a range
           of hours.

   Notes:

           Removing this header is useful for filter testing, where you want
           to force a real reload instead of getting status code "304", which
           would cause the browser to use a cached copy of the page.

           Instead of removing the header, hide-if-modified-since can also
           add or subtract a random amount of time to/from the header's
           value. You specify a range of minutes where the random factor
           should be chosen from and Privoxy does the rest. A negative value
           means subtracting, a positive value adding.

           Randomizing the value of the "If-Modified-Since:" makes it less
           likely that the server can use the time as a cookie replacement,
           but you will run into caching problems if the random range is too
           high.

           It is a good idea to only use a small negative value and let
           overwrite-last-modified handle the greater changes.

           It is also recommended to use this action together with
           crunch-if-none-match, otherwise it's more or less pointless.

   Example usage (section):

   # Let the browser revalidate but make tracking based on the time less likely.
   {+hide-if-modified-since{-60} \
    +overwrite-last-modified{randomize} \
    +crunch-if-none-match}
   /

   --------------------------------------------------------------------------

      8.5.22. hide-forwarded-for-headers

   Typical use:

           Improve privacy by not forwarding the source of the request in the
           HTTP headers.

   Effect:

           Deletes any existing "X-Forwarded-for:" HTTP header from client
           requests.

   Type:

           Boolean.

   Parameter:

           N/A

   Notes:

           It is safe and recommended to leave this on.

   Example usage:

           +hide-forwarded-for-headers

   --------------------------------------------------------------------------

      8.5.23. hide-from-header

   Typical use:

           Keep your (old and ill) browser from telling web servers your
           email address

   Effect:

           Deletes any existing "From:" HTTP header, or replaces it with the
           specified string.

   Type:

           Parameterized.

   Parameter:

           Keyword: "block", or any user defined value.

   Notes:

           The keyword "block" will completely remove the header (not to be
           confused with the block action).

           Alternately, you can specify any value you prefer to be sent to
           the web server. If you do, it is a matter of fairness not to use
           any address that is actually used by a real person.

           This action is rarely needed, as modern web browsers don't send
           "From:" headers anymore.

   Example usage:

           +hide-from-header{block}

           or

           +hide-from-header{spam-me-senseless@sittingduck.example.com}

   --------------------------------------------------------------------------

      8.5.24. hide-referrer

   Typical use:

           Conceal which link you followed to get to a particular site

   Effect:

           Deletes the "Referer:" (sic) HTTP header from the client request,
           or replaces it with a forged one.

   Type:

           Parameterized.

   Parameter:

              * "conditional-block" to delete the header completely if the
                host has changed.

              * "conditional-forge" to forge the header if the host has
                changed.

              * "block" to delete the header unconditionally.

              * "forge" to pretend to be coming from the homepage of the
                server we are talking to.

              * Any other string to set a user defined referrer.

   Notes:

           conditional-block is the only parameter, that isn't easily
           detected in the server's log file. If it blocks the referrer, the
           request will look like the visitor used a bookmark or typed in the
           address directly.

           Leaving the referrer unmodified for requests on the same host
           allows the server owner to see the visitor's "click path", but in
           most cases she could also get that information by comparing other
           parts of the log file: for example the User-Agent if it isn't a
           very common one, or the user's IP address if it doesn't change
           between different requests.

           Always blocking the referrer, or using a custom one, can lead to
           failures on servers that check the referrer before they answer any
           requests, in an attempt to prevent their content from being
           embedded or linked to elsewhere.

           Both conditional-block and forge will work with referrer checks,
           as long as content and valid referring page are on the same host.
           Most of the time that's the case.

           hide-referer is an alternate spelling of hide-referrer and the two
           can be can be freely substituted with each other. ("referrer" is
           the correct English spelling, however the HTTP specification has a
           bug - it requires it to be spelled as "referer".)

   Example usage:

           +hide-referrer{forge}

           or

           +hide-referrer{http://www.yahoo.com/}

   --------------------------------------------------------------------------

      8.5.25. hide-user-agent

   Typical use:

           Try to conceal your type of browser and client operating system

   Effect:

           Replaces the value of the "User-Agent:" HTTP header in client
           requests with the specified value.

   Type:

           Parameterized.

   Parameter:

           Any user-defined string.

   Notes:

           +---------------------------------------------------------+
           |                         Warning                         |
           |---------------------------------------------------------|
           | This can lead to problems on web sites that depend on   |
           | looking at this header in order to customize their      |
           | content for different browsers (which, by the way, is   |
           | NOT the right thing to do: good web sites work          |
           | browser-independently).                                 |
           +---------------------------------------------------------+

           Using this action in multi-user setups or wherever different types
           of browsers will access the same Privoxy is not recommended. In
           single-user, single-browser setups, you might use it to delete
           your OS version information from the headers, because it is an
           invitation to exploit known bugs for your OS. It is also
           occasionally useful to forge this in order to access sites that
           won't let you in otherwise (though there may be a good reason in
           some cases). Example of this: some MSN sites will not let Mozilla
           enter, yet forging to a Netscape 6.1 user-agent works just fine.
           (Must be just a silly MS goof, I'm sure :-).

           More information on known user-agent strings can be found at
           http://www.user-agents.org/ and
           http://en.wikipedia.org/wiki/User_agent.

   Example usage:

           +hide-user-agent{Netscape 6.1 (X11; I; Linux 2.4.18 i686)}

   --------------------------------------------------------------------------

      8.5.26. inspect-jpegs

   Typical use:

           Try to protect against a MS buffer over-run in JPEG processing

   Effect:

           Protect against a known exploit

   Type:

           Boolean.

   Parameter:

           N/A

   Notes:

           See Microsoft Security Bulletin MS04-028. JPEG images are one of
           the most common image types found across the Internet. The exploit
           as described can allow execution of code on the target system,
           giving an attacker access to the system in question by merely
           planting an altered JPEG image, which would have no obvious
           indications of what lurks inside. This action tries to prevent
           this exploit if delivered through unencrypted HTTP.

           Note that the exploit mentioned is several years old and it's
           unlikely that your client is still vulnerable against it. This
           action may be removed in one of the next releases.

   Example usage:

           +inspect-jpegs

   --------------------------------------------------------------------------

      8.5.27. kill-popups

   Typical use:

           Eliminate those annoying pop-up windows (deprecated)

   Effect:

           While loading the document, replace JavaScript code that opens
           pop-up windows with (syntactically neutral) dummy code on the fly.

   Type:

           Boolean.

   Parameter:

           N/A

   Notes:

           This action is basically a built-in, hardwired special-purpose
           filter action, but there are important differences: For
           kill-popups, the document need not be buffered, so it can be
           incrementally rendered while downloading. But kill-popups doesn't
           catch as many pop-ups as filter{all-popups} does and is not as
           smart as filter{unsolicited-popups} is.

           Think of it as a fast and efficient replacement for a filter that
           you can use if you don't want any filtering at all. Note that it
           doesn't make sense to combine it with any filter action, since as
           soon as one filter applies, the whole document needs to be
           buffered anyway, which destroys the advantage of the kill-popups
           action over its filter equivalent.

           Killing all pop-ups unconditionally is problematic. Many shops and
           banks rely on pop-ups to display forms, shopping carts etc, and
           the filter{unsolicited-popups} does a better job of catching only
           the unwanted ones.

           If the only kind of pop-ups that you want to kill are exit
           consoles (those really nasty windows that appear when you close an
           other one), you might want to use filter{js-annoyances} instead.

           This action is most appropriate for browsers that don't have any
           controls for unwanted pop-ups. Not recommended for general usage.

           This action doesn't work very reliable and may be removed in
           future releases.

   Example usage:

           +kill-popups

   --------------------------------------------------------------------------

      8.5.28. limit-connect

   Typical use:

           Prevent abuse of Privoxy as a TCP proxy relay or disable SSL for
           untrusted sites

   Effect:

           Specifies to which ports HTTP CONNECT requests are allowable.

   Type:

           Parameterized.

   Parameter:

           A comma-separated list of ports or port ranges (the latter using
           dashes, with the minimum defaulting to 0 and the maximum to 65K).

   Notes:

           By default, i.e. if no limit-connect action applies, Privoxy only
           allows HTTP CONNECT requests to port 443 (the standard, secure
           HTTPS port). Use limit-connect if more fine-grained control is
           desired for some or all destinations.

           The CONNECT methods exists in HTTP to allow access to secure
           websites ("https://" URLs) through proxies. It works very simply:
           the proxy connects to the server on the specified port, and then
           short-circuits its connections to the client and to the remote
           server. This means CONNECT-enabled proxies can be used as TCP
           relays very easily.

           Privoxy relays HTTPS traffic without seeing the decoded content.
           Websites can leverage this limitation to circumvent Privoxy's
           filters. By specifying an invalid port range you can disable HTTPS
           entirely. If you plan to disable SSL by default, consider enabling
           treat-forbidden-connects-like-blocks as well, to be able to
           quickly create exceptions.

   Example usages:

+limit-connect{443}                   # This is the default and need not be specified.
+limit-connect{80,443}                # Ports 80 and 443 are OK.
+limit-connect{-3, 7, 20-100, 500-}   # Ports less than 3, 7, 20 to 100 and above 500 are OK.
+limit-connect{-}                     # All ports are OK
+limit-connect{,}                     # No HTTPS/SSL traffic is allowed

   --------------------------------------------------------------------------

      8.5.29. prevent-compression

   Typical use:

           Ensure that servers send the content uncompressed, so it can be
           passed through filters.

   Effect:

           Removes the Accept-Encoding header which can be used to ask for
           compressed transfer.

   Type:

           Boolean.

   Parameter:

           N/A

   Notes:

           More and more websites send their content compressed by default,
           which is generally a good idea and saves bandwidth. But the
           filter, deanimate-gifs and kill-popups actions need access to the
           uncompressed data.

           When compiled with zlib support (available since Privoxy 3.0.7),
           content that should be filtered is decompressed on-the-fly and you
           don't have to worry about this action. If you are using an older
           Privoxy version, or one that hasn't been compiled with zlib
           support, this action can be used to convince the server to send
           the content uncompressed.

           Most text-based instances compress very well, the size is seldom
           decreased by less than 50%, for markup-heavy instances like news
           feeds saving more than 90% of the original size isn't unusual.

           Not using compression will therefore slow down the transfer, and
           you should only enable this action if you really need it. As of
           Privoxy 3.0.7 it's disabled in all predefined action settings.

           Note that some (rare) ill-configured sites don't handle requests
           for uncompressed documents correctly. Broken PHP applications tend
           to send an empty document body, some IIS versions only send the
           beginning of the content. If you enable prevent-compression per
           default, you might want to add exceptions for those sites. See the
           example for how to do that.

   Example usage (sections):

           # Selectively turn off compression, and enable a filter
           #
           { +filter{tiny-textforms} +prevent-compression }
           # Match only these sites
            .google.
            sourceforge.net
            sf.net

           # Or instead, we could set a universal default:
           #
           { +prevent-compression }
            / # Match all sites

           # Then maybe make exceptions for broken sites:
           #
           { -prevent-compression }
           .compusa.com/

   --------------------------------------------------------------------------

      8.5.30. overwrite-last-modified

   Typical use:

           Prevent yet another way to track the user's steps between
           sessions.

   Effect:

           Deletes the "Last-Modified:" HTTP server header or modifies its
           value.

   Type:

           Parameterized.

   Parameter:

           One of the keywords: "block", "reset-to-request-time" and
           "randomize"

   Notes:

           Removing the "Last-Modified:" header is useful for filter testing,
           where you want to force a real reload instead of getting status
           code "304", which would cause the browser to reuse the old version
           of the page.

           The "randomize" option overwrites the value of the
           "Last-Modified:" header with a randomly chosen time between the
           original value and the current time. In theory the server could
           send each document with a different "Last-Modified:" header to
           track visits without using cookies. "Randomize" makes it
           impossible and the browser can still revalidate cached documents.

           "reset-to-request-time" overwrites the value of the
           "Last-Modified:" header with the current time. You could use this
           option together with hided-if-modified-since to further customize
           your random range.

           The preferred parameter here is "randomize". It is safe to use, as
           long as the time settings are more or less correct. If the server
           sets the "Last-Modified:" header to the time of the request, the
           random range becomes zero and the value stays the same. Therefore
           you should later randomize it a second time with
           hided-if-modified-since, just to be sure.

           It is also recommended to use this action together with
           crunch-if-none-match.

   Example usage:

           # Let the browser revalidate without being tracked across sessions
           { +hide-if-modified-since{-60} \
            +overwrite-last-modified{randomize} \
            +crunch-if-none-match}
           /

   --------------------------------------------------------------------------

      8.5.31. redirect

   Typical use:

           Redirect requests to other sites.

   Effect:

           Convinces the browser that the requested document has been moved
           to another location and the browser should get it from there.

   Type:

           Parameterized

   Parameter:

           An absolute URL or a single pcrs command.

   Notes:

           Requests to which this action applies are answered with a HTTP
           redirect to URLs of your choosing. The new URL is either provided
           as parameter, or derived by applying a single pcrs command to the
           original URL.

           This action will be ignored if you use it together with block. It
           can be combined with fast-redirects{check-decoded-url} to redirect
           to a decoded version of a rewritten URL.

           Use this action carefully, make sure not to create redirection
           loops and be aware that using your own redirects might make it
           possible to fingerprint your requests.

   Example usages:

           # Replace example.com's style sheet with another one
           { +redirect{http://localhost/css-replacements/example.com.css} }
            example.com/stylesheet\.css

           # Create a short, easy to remember nickname for a favorite site
           # (relies on the browser accept and forward invalid URLs to Privoxy)
           { +redirect{http://www.privoxy.org/user-manual/actions-file.html} }
            a

           # Always use the expanded view for Undeadly.org articles
           # (Note the $ at the end of the URL pattern to make sure
           # the request for the rewritten URL isn't redirected as well)
           {+redirect{s@$@&mode=expanded@}}
           undeadly.org/cgi\?action=article&sid=\d*$

   --------------------------------------------------------------------------

      8.5.32. send-vanilla-wafer

   Typical use:

           Feed log analysis scripts with useless data.

   Effect:

           Sends a cookie with each request stating that you do not accept
           any copyright on cookies sent to you, and asking the site operator
           not to track you.

   Type:

           Boolean.

   Parameter:

           N/A

   Notes:

           The vanilla wafer is a (relatively) unique header and could
           conceivably be used to track you.

           This action is rarely used and not enabled in the default
           configuration.

   Example usage:

           +send-vanilla-wafer

   --------------------------------------------------------------------------

      8.5.33. send-wafer

   Typical use:

           Send custom cookies or feed log analysis scripts with even more
           useless data.

   Effect:

           Sends a custom, user-defined cookie with each request.

   Type:

           Multi-value.

   Parameter:

           A string of the form "name=value".

   Notes:

           Being multi-valued, multiple instances of this action can apply to
           the same request, resulting in multiple cookies being sent.

           This action is rarely used and not enabled in the default
           configuration.

   Example usage (section):

           {+send-wafer{UsingPrivoxy=true}}
           my-internal-testing-server.void

   --------------------------------------------------------------------------

      8.5.34. server-header-filter

   Typical use:

           Rewrite or remove single server headers.

   Effect:

           All server headers to which this action applies are filtered
           on-the-fly through the specified regular expression based
           substitutions.

   Type:

           Parameterized.

   Parameter:

           The name of a server-header filter, as defined in one of the
           filter files.

   Notes:

           Server-header filters are applied to each header on its own, not
           to all at once. This makes it easier to diagnose problems, but on
           the downside you can't write filters that only change header x if
           header y's value is z. You can do that by using tags though.

           Server-header filters are executed after the other header actions
           have finished and use their output as input.

           Please refer to the filter file chapter to learn which
           server-header filters are available by default, and how to create
           your own.

   Example usage (section):

           {+server-header-filter{html-to-xml}}
           example.org/xml-instance-that-is-delivered-as-html

           {+server-header-filter{xml-to-html}}
           example.org/instance-that-is-delivered-as-xml-but-is-not


   --------------------------------------------------------------------------

      8.5.35. server-header-tagger

   Typical use:

           Enable or disable filters based on the Content-Type header.

   Effect:

           Server headers to which this action applies are filtered
           on-the-fly through the specified regular expression based
           substitutions, the result is used as tag.

   Type:

           Parameterized.

   Parameter:

           The name of a server-header tagger, as defined in one of the
           filter files.

   Notes:

           Server-header taggers are applied to each header on its own, and
           as the header isn't modified, each tagger "sees" the original.

           Server-header taggers are executed before all other header actions
           that modify server headers. Their tags can be used to control all
           of the other server-header actions, the content filters and the
           crunch actions (redirect and block).

           Obviously crunching based on tags created by server-header taggers
           doesn't prevent the request from showing up in the server's log
           file.

   Example usage (section):

           # Tag every request with the content type declared by the server
           {+server-header-tagger{content-type}}
           /


   --------------------------------------------------------------------------

      8.5.36. session-cookies-only

   Typical use:

           Allow only temporary "session" cookies (for the current browser
           session only).

   Effect:

           Deletes the "expires" field from "Set-Cookie:" server headers.
           Most browsers will not store such cookies permanently and forget
           them in between sessions.

   Type:

           Boolean.

   Parameter:

           N/A

   Notes:

           This is less strict than crunch-incoming-cookies /
           crunch-outgoing-cookies and allows you to browse websites that
           insist or rely on setting cookies, without compromising your
           privacy too badly.

           Most browsers will not permanently store cookies that have been
           processed by session-cookies-only and will forget about them
           between sessions. This makes profiling cookies useless, but won't
           break sites which require cookies so that you can log in for
           transactions. This is generally turned on for all sites, and is
           the recommended setting.

           It makes no sense at all to use session-cookies-only together with
           crunch-incoming-cookies or crunch-outgoing-cookies. If you do,
           cookies will be plainly killed.

           Note that it is up to the browser how it handles such cookies
           without an "expires" field. If you use an exotic browser, you
           might want to try it out to be sure.

           This setting also has no effect on cookies that may have been
           stored previously by the browser before starting Privoxy. These
           would have to be removed manually.

           Privoxy also uses the content-cookies filter to block some types
           of cookies. Content cookies are not effected by
           session-cookies-only.

   Example usage:

           +session-cookies-only

   --------------------------------------------------------------------------

      8.5.37. set-image-blocker

   Typical use:

           Choose the replacement for blocked images

   Effect:

           This action alone doesn't do anything noticeable. If both block
           and handle-as-image also apply, i.e. if the request is to be
           blocked as an image, then the parameter of this action decides
           what will be sent as a replacement.

   Type:

           Parameterized.

   Parameter:

              * "pattern" to send a built-in checkerboard pattern image. The
                image is visually decent, scales very well, and makes it
                obvious where banners were busted.

              * "blank" to send a built-in transparent image. This makes
                banners disappear completely, but makes it hard to detect
                where Privoxy has blocked images on a given page and
                complicates troubleshooting if Privoxy has blocked innocent
                images, like navigation icons.

              * "target-url" to send a redirect to target-url. You can
                redirect to any image anywhere, even in your local filesystem
                via "file:///" URL. (But note that not all browsers support
                redirecting to a local file system).

                A good application of redirects is to use special
                Privoxy-built-in URLs, which send the built-in images, as
                target-url. This has the same visual effect as specifying
                "blank" or "pattern" in the first place, but enables your
                browser to cache the replacement image, instead of requesting
                it over and over again.

   Notes:

           The URLs for the built-in images are
           "http://config.privoxy.org/send-banner?type=type", where type is
           either "blank" or "pattern".

           There is a third (advanced) type, called "auto". It is NOT to be
           used in set-image-blocker, but meant for use from filters. Auto
           will select the type of image that would have applied to the
           referring page, had it been an image.

   Example usage:

           Built-in pattern:

           +set-image-blocker{pattern}

           Redirect to the BSD daemon:

           +set-image-blocker{http://www.freebsd.org/gifs/dae_up3.gif}

           Redirect to the built-in pattern for better caching:

          +set-image-blocker{http://config.privoxy.org/send-banner?type=pattern}

   --------------------------------------------------------------------------

      8.5.38. treat-forbidden-connects-like-blocks

   Typical use:

           Block forbidden connects with an easy to find error message.

   Effect:

           If this action is enabled, Privoxy no longer makes a difference
           between forbidden connects and ordinary blocks.

   Type:

           Boolean

   Parameter:

           N/A

   Notes:

           By default Privoxy answers forbidden "Connect" requests with a
           short error message inside the headers. If the browser doesn't
           display headers (most don't), you just see an empty page.

           With this action enabled, Privoxy displays the message that is
           used for ordinary blocks instead. If you decide to make an
           exception for the page in question, you can do so by following the
           "See why" link.

           For "Connect" requests the clients tell Privoxy which host they
           are interested in, but not which document they plan to get later.
           As a result, the "Go there anyway" wouldn't work and is therefore
           suppressed.

   Example usage:

           +treat-forbidden-connects-like-blocks

   --------------------------------------------------------------------------

    8.5.39. Summary

   Note that many of these actions have the potential to cause a page to
   misbehave, possibly even not to display at all. There are many ways a site
   designer may choose to design his site, and what HTTP header content, and
   other criteria, he may depend on. There is no way to have hard and fast
   rules for all sites. See the Appendix for a brief example on
   troubleshooting actions.

   --------------------------------------------------------------------------

  8.6. Aliases

   Custom "actions", known to Privoxy as "aliases", can be defined by
   combining other actions. These can in turn be invoked just like the
   built-in actions. Currently, an alias name can contain any character
   except space, tab, "=", "{" and "}", but we strongly recommend that you
   only use "a" to "z", "0" to "9", "+", and "-". Alias names are not case
   sensitive, and are not required to start with a "+" or "-" sign, since
   they are merely textually expanded.

   Aliases can be used throughout the actions file, but they must be defined
   in a special section at the top of the file! And there can only be one
   such section per actions file. Each actions file may have its own alias
   section, and the aliases defined in it are only visible within that file.

   There are two main reasons to use aliases: One is to save typing for
   frequently used combinations of actions, the other one is a gain in
   flexibility: If you decide once how you want to handle shops by defining
   an alias called "shop", you can later change your policy on shops in one
   place, and your changes will take effect everywhere in the actions file
   where the "shop" alias is used. Calling aliases by their purpose also
   makes your actions files more readable.

   Currently, there is one big drawback to using aliases, though: Privoxy's
   built-in web-based action file editor honors aliases when reading the
   actions files, but it expands them before writing. So the effects of your
   aliases are of course preserved, but the aliases themselves are lost when
   you edit sections that use aliases with it.

   Now let's define some aliases...

 # Useful custom aliases we can use later.
 #
 # Note the (required!) section header line and that this section
 # must be at the top of the actions file!
 #
 {{alias}}

 # These aliases just save typing later:
 # (Note that some already use other aliases!)
 #
 +crunch-all-cookies = +crunch-incoming-cookies +crunch-outgoing-cookies
 -crunch-all-cookies = -crunch-incoming-cookies -crunch-outgoing-cookies
 +block-as-image      = +block +handle-as-image
 allow-all-cookies   = -crunch-all-cookies -session-cookies-only -filter{content-cookies}

 # These aliases define combinations of actions
 # that are useful for certain types of sites:
 #
 fragile     = -block -filter -crunch-all-cookies -fast-redirects -hide-referrer -kill-popups -prevent-compression

 shop        = -crunch-all-cookies -filter{all-popups} -kill-popups

 # Short names for other aliases, for really lazy people ;-)
 #
 c0 = +crunch-all-cookies
 c1 = -crunch-all-cookies

   ...and put them to use. These sections would appear in the lower part of
   an actions file and define exceptions to the default actions (as specified
   further up for the "/" pattern):

    # These sites are either very complex or very keen on
    # user data and require minimal interference to work:
    #
    {fragile}
    .office.microsoft.com
    .windowsupdate.microsoft.com
    # Gmail is really mail.google.com, not gmail.com
    mail.google.com

    # Shopping sites:
    # Allow cookies (for setting and retrieving your customer data)
    #
    {shop}
    .quietpc.com
    .worldpay.com   # for quietpc.com
    mybank.example.com

    # These shops require pop-ups:
    #
    {-kill-popups -filter{all-popups} -filter{unsolicited-popups}}
     .dabs.com
     .overclockers.co.uk

   Aliases like "shop" and "fragile" are typically used for "problem" sites
   that require more than one action to be disabled in order to function
   properly.

   --------------------------------------------------------------------------

  8.7. Actions Files Tutorial

   The above chapters have shown which actions files there are and how they
   are organized, how actions are specified and applied to URLs, how patterns
   work, and how to define and use aliases. Now, let's look at an example
   default.action and user.action file and see how all these pieces come
   together:

   --------------------------------------------------------------------------

    8.7.1. default.action

   Every config file should start with a short comment stating its purpose:

   # Sample default.action file <ijbswa-developers@lists.sourceforge.net>

   Then, since this is the default.action file, the first section is a
   special section for internal use that you needn't change or worry about:

   ##########################################################################
   # Settings -- Don't change! For internal Privoxy use ONLY.
   ##########################################################################

   {{settings}}
   for-privoxy-version=3.0

   After that comes the (optional) alias section. We'll use the example
   section from the above chapter on aliases, that also explains why and how
   aliases are used:

##########################################################################
# Aliases
##########################################################################
{{alias}}

 # These aliases just save typing later:
 # (Note that some already use other aliases!)
 #
 +crunch-all-cookies = +crunch-incoming-cookies +crunch-outgoing-cookies
 -crunch-all-cookies = -crunch-incoming-cookies -crunch-outgoing-cookies
 +block-as-image      = +block +handle-as-image
 mercy-for-cookies   = -crunch-all-cookies -session-cookies-only -filter{content-cookies}

 # These aliases define combinations of actions
 # that are useful for certain types of sites:
 #
 fragile     = -block -filter -crunch-all-cookies -fast-redirects -hide-referrer -kill-popups
 shop        = -crunch-all-cookies -filter{all-popups} -kill-popups

   Now come the regular sections, i.e. sets of actions, accompanied by URL
   patterns to which they apply. Remember all actions are disabled when
   matching starts, so we have to explicitly enable the ones we want.

   The first regular section is probably the most important. It has only one
   pattern, "/", but this pattern matches all URLs. Therefore, the set of
   actions used in this "default" section will be applied to all requests as
   a start. It can be partly or wholly overridden by later matches further
   down this file, or in user.action, but it will still be largely
   responsible for your overall browsing experience.

   Again, at the start of matching, all actions are disabled, so there is no
   need to disable any actions here. (Remember: a "+" preceding the action
   name enables the action, a "-" disables!). Also note how this long line
   has been made more readable by splitting it into multiple lines with line
   continuation.

   ##########################################################################
   # "Defaults" section:
   ##########################################################################
    { \
    +deanimate-gifs \
    +filter{html-annoyances} \
    +filter{refresh-tags} \
    +filter{webbugs} \
    +filter{ie-exploits} \
    +hide-forwarded-for-headers \
    +hide-from-header{block} \
    +hide-referrer{forge} \
    +prevent-compression \
    +session-cookies-only \
    +set-image-blocker{pattern} \
    }
    / # forward slash will match *all* potential URL patterns.

   The default behavior is now set.

   The first of our specialized sections is concerned with "fragile" sites,
   i.e. sites that require minimum interference, because they are either very
   complex or very keen on tracking you (and have mechanisms in place that
   make them unusable for people who avoid being tracked). We will simply use
   our pre-defined fragile alias instead of stating the list of actions
   explicitly:

   ##########################################################################
   # Exceptions for sites that'll break under the default action set:
   ##########################################################################

   # "Fragile" Use a minimum set of actions for these sites (see alias above):
   #
   { fragile }
   .office.microsoft.com           # surprise, surprise!
   .windowsupdate.microsoft.com
   mail.google.com

   Shopping sites are not as fragile, but they typically require cookies to
   log in, and pop-up windows for shopping carts or item details. Again,
   we'll use a pre-defined alias:

   # Shopping sites:
   #
   { shop }
   .quietpc.com
   .worldpay.com   # for quietpc.com
   .jungle.com
   .scan.co.uk

   The fast-redirects action, which we enabled per default above, breaks some
   sites. So disable it for popular sites where we know it misbehaves:

   { -fast-redirects }
   login.yahoo.com
   edit.*.yahoo.com
   .google.com
   .altavista.com/.*(like|url|link):http
   .altavista.com/trans.*urltext=http
   .nytimes.com

   It is important that Privoxy knows which URLs belong to images, so that if
   they are to be blocked, a substitute image can be sent, rather than an
   HTML page. Contacting the remote site to find out is not an option, since
   it would destroy the loading time advantage of banner blocking, and it
   would feed the advertisers (in terms of money and information). We can
   mark any URL as an image with the handle-as-image action, and marking all
   URLs that end in a known image file extension is a good start:

   ##########################################################################
   # Images:
   ##########################################################################

   # Define which file types will be treated as images, in case they get
   # blocked further down this file:
   #
   { +handle-as-image }
   /.*\.(gif|jpe?g|png|bmp|ico)$

   And then there are known banner sources. They often use scripts to
   generate the banners, so it won't be visible from the URL that the request
   is for an image. Hence we block them and mark them as images in one go,
   with the help of our +block-as-image alias defined above. (We could of
   course just as well use +block +handle-as-image here.) Remember that the
   type of the replacement image is chosen by the set-image-blocker action.
   Since all URLs have matched the default section with its
   +set-image-blocker{pattern} action before, it still applies and needn't be
   repeated:

   # Known ad generators:
   #
   { +block-as-image }
   ar.atwola.com
   .ad.doubleclick.net
   .ad.*.doubleclick.net
   .a.yimg.com/(?:(?!/i/).)*$
   .a[0-9].yimg.com/(?:(?!/i/).)*$
   bs*.gsanet.com
   .qkimg.net

   One of the most important jobs of Privoxy is to block banners. Many of
   these can be "blocked" by the filter{banners-by-size} action, which we
   enabled above, and which deletes the references to banner images from the
   pages while they are loaded, so the browser doesn't request them anymore,
   and hence they don't need to be blocked here. But this naturally doesn't
   catch all banners, and some people choose not to use filters, so we need a
   comprehensive list of patterns for banner URLs here, and apply the block
   action to them.

   First comes many generic patterns, which do most of the work, by matching
   typical domain and path name components of banners. Then comes a list of
   individual patterns for specific sites, which is omitted here to keep the
   example short:

   ##########################################################################
   # Block these fine banners:
   ##########################################################################
   { +block }

   # Generic patterns:
   #
   ad*.
   .*ads.
   banner?.
   count*.
   /.*count(er)?\.(pl|cgi|exe|dll|asp|php[34]?)
   /(?:.*/)?(publicite|werbung|rekla(ma|me|am)|annonse|maino(kset|nta|s)?)/

   # Site-specific patterns (abbreviated):
   #
   .hitbox.com

   It's quite remarkable how many advertisers actually call their banner
   servers ads.company.com, or call the directory in which the banners are
   stored simply "banners". So the above generic patterns are surprisingly
   effective.

   But being very generic, they necessarily also catch URLs that we don't
   want to block. The pattern .*ads. e.g. catches "nasty-ads.nasty-corp.com"
   as intended, but also "downloads.sourcefroge.net" or
   "adsl.some-provider.net." So here come some well-known exceptions to the
   +block section above.

   Note that these are exceptions to exceptions from the default! Consider
   the URL "downloads.sourcefroge.net": Initially, all actions are
   deactivated, so it wouldn't get blocked. Then comes the defaults section,
   which matches the URL, but just deactivates the block action once again.
   Then it matches .*ads., an exception to the general non-blocking policy,
   and suddenly +block applies. And now, it'll match .*loads., where -block
   applies, so (unless it matches again further down) it ends up with no
   block action applying.

   ##########################################################################
   # Save some innocent victims of the above generic block patterns:
   ##########################################################################

   # By domain:
   #
   { -block }
   adv[io]*.  # (for advogato.org and advice.*)
   adsl.      # (has nothing to do with ads)
   adobe.     # (has nothing to do with ads either)
   ad[ud]*.   # (adult.* and add.*)
   .edu       # (universities don't host banners (yet!))
   .*loads.   # (downloads, uploads etc)

   # By path:
   #
   /.*loads/

   # Site-specific:
   #
   www.globalintersec.com/adv # (adv = advanced)
   www.ugu.com/sui/ugu/adv

   Filtering source code can have nasty side effects, so make an exception
   for our friends at sourceforge.net, and all paths with "cvs" in them. Note
   that -filter disables all filters in one fell swoop!

   # Don't filter code!
   #
   { -filter }
   /(.*/)?cvs
   bugzilla.
   developer.
   wiki.
   .sourceforge.net

   The actual default.action is of course much more comprehensive, but we
   hope this example made clear how it works.

   --------------------------------------------------------------------------

    8.7.2. user.action

   So far we are painting with a broad brush by setting general policies,
   which would be a reasonable starting point for many people. Now, you might
   want to be more specific and have customized rules that are more suitable
   to your personal habits and preferences. These would be for narrowly
   defined situations like your ISP or your bank, and should be placed in
   user.action, which is parsed after all other actions files and hence has
   the last word, over-riding any previously defined actions. user.action is
   also a safe place for your personal settings, since default.action is
   actively maintained by the Privoxy developers and you'll probably want to
   install updated versions from time to time.

   So let's look at a few examples of things that one might typically do in
   user.action:

   # My user.action file. <fred@example.com>

   As aliases are local to the actions file that they are defined in, you
   can't use the ones from default.action, unless you repeat them here:

# Aliases are local to the file they are defined in.
# (Re-)define aliases for this file:
#
{{alias}}
#
# These aliases just save typing later, and the alias names should
# be self explanatory.
#
+crunch-all-cookies = +crunch-incoming-cookies +crunch-outgoing-cookies
-crunch-all-cookies = -crunch-incoming-cookies -crunch-outgoing-cookies
 allow-all-cookies  = -crunch-all-cookies -session-cookies-only
 allow-popups       = -filter{all-popups} -kill-popups
+block-as-image     = +block +handle-as-image
-block-as-image     = -block

# These aliases define combinations of actions that are useful for
# certain types of sites:
#
fragile     = -block -crunch-all-cookies -filter -fast-redirects -hide-referrer -kill-popups
shop        = -crunch-all-cookies allow-popups

# Allow ads for selected useful free sites:
#
allow-ads   = -block -filter{banners-by-size} -filter{banners-by-link}

# Alias for specific file types that are text, but might have conflicting
# MIME types. We want the browser to force these to be text documents.
handle-as-text = -filter +-content-type-overwrite{text/plain} +-force-text-mode -hide-content-disposition



   Say you have accounts on some sites that you visit regularly, and you
   don't want to have to log in manually each time. So you'd like to allow
   persistent cookies for these sites. The allow-all-cookies alias defined
   above does exactly that, i.e. it disables crunching of cookies in any
   direction, and the processing of cookies to make them only temporary.

   { allow-all-cookies }
    sourceforge.net
    .yahoo.com
    .msdn.microsoft.com
    .redhat.com

   Your bank is allergic to some filter, but you don't know which, so you
   disable them all:

   { -filter }
    .your-home-banking-site.com

   Some file types you may not want to filter for various reasons:

   # Technical documentation is likely to contain strings that might
   # erroneously get altered by the JavaScript-oriented filters:
   #
   .tldp.org
   /(.*/)?selfhtml/

   # And this stupid host sends streaming video with a wrong MIME type,
   # so that Privoxy thinks it is getting HTML and starts filtering:
   #
   stupid-server.example.com/

   Example of a simple block action. Say you've seen an ad on your favourite
   page on example.com that you want to get rid of. You have right-clicked
   the image, selected "copy image location" and pasted the URL below while
   removing the leading http://, into a { +block } section. Note that {
   +handle-as-image } need not be specified, since all URLs ending in .gif
   will be tagged as images by the general rules as set in default.action
   anyway:

   { +block }
    www.example.com/nasty-ads/sponsor\.gif
    another.example.net/more/junk/here/

   The URLs of dynamically generated banners, especially from large banner
   farms, often don't use the well-known image file name extensions, which
   makes it impossible for Privoxy to guess the file type just by looking at
   the URL. You can use the +block-as-image alias defined above for these
   cases. Note that objects which match this rule but then turn out NOT to be
   an image are typically rendered as a "broken image" icon by the browser.
   Use cautiously.

   { +block-as-image }
    .doubleclick.net
    .fastclick.net
    /Realmedia/ads/
    ar.atwola.com/

   Now you noticed that the default configuration breaks Forbes Magazine, but
   you were too lazy to find out which action is the culprit, and you were
   again too lazy to give feedback, so you just used the fragile alias on the
   site, and -- whoa! -- it worked. The fragile aliases disables those
   actions that are most likely to break a site. Also, good for testing
   purposes to see if it is Privoxy that is causing the problem or not. We
   later find other regular sites that misbehave, and add those to our
   personalized list of troublemakers:

   { fragile }
    .forbes.com
    webmail.example.com
    .mybank.com

   You like the "fun" text replacements in default.filter, but it is disabled
   in the distributed actions file. So you'd like to turn it on in your
   private, update-safe config, once and for all:

   { +filter{fun} }
    / # For ALL sites!

   Note that the above is not really a good idea: There are exceptions to the
   filters in default.action for things that really shouldn't be filtered,
   like code on CVS->Web interfaces. Since user.action has the last word,
   these exceptions won't be valid for the "fun" filtering specified here.

   You might also worry about how your favourite free websites are funded,
   and find that they rely on displaying banner advertisements to survive. So
   you might want to specifically allow banners for those sites that you feel
   provide value to you:

   { allow-ads }
    .sourceforge.net
    .slashdot.org
    .osdn.net

   Note that allow-ads has been aliased to -block, -filter{banners-by-size},
   and -filter{banners-by-link} above.

   Invoke another alias here to force an over-ride of the MIME type
   application/x-sh which typically would open a download type dialog. In my
   case, I want to look at the shell script, and then I can save it should I
   choose to.

   { handle-as-text }
    /.*\.sh$

   user.action is generally the best place to define exceptions and additions
   to the default policies of default.action. Some actions are safe to have
   their default policies set here though. So let's set a default policy to
   have a "blank" image as opposed to the checkerboard pattern for ALL sites.
   "/" of course matches all URL paths and patterns:

   { +set-image-blocker{blank} }
   / # ALL sites

   --------------------------------------------------------------------------

9. Filter Files

   On-the-fly text substitutions need to be defined in a "filter file". Once
   defined, they can then be invoked as an "action".

   Privoxy supports three different filter actions: filter to rewrite the
   content that is send to the client, client-header-filter to rewrite
   headers that are send by the client, and server-header-filter to rewrite
   headers that are send by the server.

   Privoxy also supports two tagger actions: client-header-tagger and
   server-header-tagger. Taggers and filters use the same syntax in the
   filter files, the difference is that taggers don't modify the text they
   are filtering, but use a rewritten version of the filtered text as tag.
   The tags can then be used to change the applying actions through sections
   with tag-patterns.

   Multiple filter files can be defined through the filterfile config
   directive. The filters as supplied by the developers are located in
   default.filter. It is recommended that any locally defined or modified
   filters go in a separately defined file such as user.filter.

   Common tasks for content filters are to eliminate common annoyances in
   HTML and JavaScript, such as pop-up windows, exit consoles, crippled
   windows without navigation tools, the infamous <BLINK> tag etc, to
   suppress images with certain width and height attributes (standard banner
   sizes or web-bugs), or just to have fun.

   Enabled content filters are applied to any content whose "Content Type"
   header is recognised as a sign of text-based content, with the exception
   of text/plain. Use the force-text-mode action to also filter other
   content.

   Substitutions are made at the source level, so if you want to "roll your
   own" filters, you should first be familiar with HTML syntax, and, of
   course, regular expressions.

   Just like the actions files, the filter file is organized in sections,
   which are called filters here. Each filter consists of a heading line,
   that starts with one of the keywords FILTER:, CLIENT-HEADER-FILTER: or
   SERVER-HEADER-FILTER: followed by the filter's name, and a short (one
   line) description of what it does. Below that line come the jobs, i.e.
   lines that define the actual text substitutions. By convention, the name
   of a filter should describe what the filter eliminates. The comment is
   used in the web-based user interface.

   Once a filter called name has been defined in the filter file, it can be
   invoked by using an action of the form +filter{name} in any actions file.

   Filter definitions start with a header line that contains the filter type,
   the filter name and the filter description. A content filter header line
   for a filter called "foo" could look like this:

   FILTER: foo Replace all "foo" with "bar"

   Below that line, and up to the next header line, come the jobs that define
   what text replacements the filter executes. They are specified in a syntax
   that imitates Perl's s/// operator. If you are familiar with Perl, you
   will find this to be quite intuitive, and may want to look at the PCRS
   documentation for the subtle differences to Perl behaviour. Most notably,
   the non-standard option letter U is supported, which turns the default to
   ungreedy matching.

   If you are new to "Regular Expressions", you might want to take a look at
   the Appendix on regular expressions, and see the Perl manual for the s///
   operator's syntax and Perl-style regular expressions in general. The below
   examples might also help to get you started.

   --------------------------------------------------------------------------

  9.1. Filter File Tutorial

   Now, let's complete our "foo" content filter. We have already defined the
   heading, but the jobs are still missing. Since all it does is to replace
   "foo" with "bar", there is only one (trivial) job needed:

   s/foo/bar/

   But wait! Didn't the comment say that all occurrences of "foo" should be
   replaced? Our current job will only take care of the first "foo" on each
   page. For global substitution, we'll need to add the g option:

   s/foo/bar/g

   Our complete filter now looks like this:

   FILTER: foo Replace all "foo" with "bar"
   s/foo/bar/g

   Let's look at some real filters for more interesting examples. Here you
   see a filter that protects against some common annoyances that arise from
   JavaScript abuse. Let's look at its jobs one after the other:

FILTER: js-annoyances Get rid of particularly annoying JavaScript abuse

# Get rid of JavaScript referrer tracking. Test page: http://www.randomoddness.com/untitled.htm
#
s|(<script.*)document\.referrer(.*</script>)|$1"Not Your Business!"$2|Usg

   Following the header line and a comment, you see the job. Note that it
   uses | as the delimiter instead of /, because the pattern contains a
   forward slash, which would otherwise have to be escaped by a backslash
   (\).

   Now, let's examine the pattern: it starts with the text <script.* enclosed
   in parentheses. Since the dot matches any character, and * means: "Match
   an arbitrary number of the element left of myself", this matches
   "<script", followed by any text, i.e. it matches the whole page, from the
   start of the first <script> tag.

   That's more than we want, but the pattern continues: document\.referrer
   matches only the exact string "document.referrer". The dot needed to be
   escaped, i.e. preceded by a backslash, to take away its special meaning as
   a joker, and make it just a regular dot. So far, the meaning is: Match
   from the start of the first <script> tag in a the page, up to, and
   including, the text "document.referrer", if both are present in the page
   (and appear in that order).

   But there's still more pattern to go. The next element, again enclosed in
   parentheses, is .*</script>. You already know what .* means, so the whole
   pattern translates to: Match from the start of the first <script> tag in a
   page to the end of the last <script> tag, provided that the text
   "document.referrer" appears somewhere in between.

   This is still not the whole story, since we have ignored the options and
   the parentheses: The portions of the page matched by sub-patterns that are
   enclosed in parentheses, will be remembered and be available through the
   variables $1, $2, ... in the substitute. The U option switches to ungreedy
   matching, which means that the first .* in the pattern will only "eat up"
   all text in between "<script" and the first occurrence of
   "document.referrer", and that the second .* will only span the text up to
   the first "</script>" tag. Furthermore, the s option says that the match
   may span multiple lines in the page, and the g option again means that the
   substitution is global.

   So, to summarize, the pattern means: Match all scripts that contain the
   text "document.referrer". Remember the parts of the script from (and
   including) the start tag up to (and excluding) the string
   "document.referrer" as $1, and the part following that string, up to and
   including the closing tag, as $2.

   Now the pattern is deciphered, but wasn't this about substituting things?
   So lets look at the substitute: $1"Not Your Business!"$2 is easy to read:
   The text remembered as $1, followed by "Not Your Business!" (including the
   quotation marks!), followed by the text remembered as $2. This produces an
   exact copy of the original string, with the middle part (the
   "document.referrer") replaced by "Not Your Business!".

   The whole job now reads: Replace "document.referrer" by "Not Your
   Business!" wherever it appears inside a <script> tag. Note that this job
   won't break JavaScript syntax, since both the original and the replacement
   are syntactically valid string objects. The script just won't have access
   to the referrer information anymore.

   We'll show you two other jobs from the JavaScript taming department, but
   this time only point out the constructs of special interest:

   # The status bar is for displaying link targets, not pointless blahblah
   #
   s/window\.status\s*=\s*(['"]).*?\1/dUmMy=1/ig

   \s stands for whitespace characters (space, tab, newline, carriage return,
   form feed), so that \s* means: "zero or more whitespace". The ? in .*?
   makes this matching of arbitrary text ungreedy. (Note that the U option is
   not set). The ['"] construct means: "a single or a double quote". Finally,
   \1 is a back-reference to the first parenthesis just like $1 above, with
   the difference that in the pattern, a backslash indicates a
   back-reference, whereas in the substitute, it's the dollar.

   So what does this job do? It replaces assignments of single- or
   double-quoted strings to the "window.status" object with a dummy
   assignment (using a variable name that is hopefully odd enough not to
   conflict with real variables in scripts). Thus, it catches many cases
   where e.g. pointless descriptions are displayed in the status bar instead
   of the link target when you move your mouse over links.

# Kill OnUnload popups. Yummy. Test: http://www.zdnet.com/zdsubs/yahoo/tree/yfs.html
#
s/(<body [^>]*)onunload(.*>)/$1never$2/iU

   Including the OnUnload event binding in the HTML DOM was a CRIME. When I
   close a browser window, I want it to close and die. Basta. This job
   replaces the "onunload" attribute in "<body>" tags with the dummy word
   never. Note that the i option makes the pattern matching case-insensitive.
   Also note that ungreedy matching alone doesn't always guarantee a minimal
   match: In the first parenthesis, we had to use [^>]* instead of .* to
   prevent the match from exceeding the <body> tag if it doesn't contain
   "OnUnload", but the page's content does.

   The last example is from the fun department:

   FILTER: fun Fun text replacements

   # Spice the daily news:
   #
   s/microsoft(?!\.com)/MicroSuck/ig

   Note the (?!\.com) part (a so-called negative lookahead) in the job's
   pattern, which means: Don't match, if the string ".com" appears directly
   following "microsoft" in the page. This prevents links to microsoft.com
   from being trashed, while still replacing the word everywhere else.

   # Buzzword Bingo (example for extended regex syntax)
   #
   s* industry[ -]leading \
   |  cutting[ -]edge \
   |  customer[ -]focused \
   |  market[ -]driven \
   |  award[ -]winning # Comments are OK, too! \
   |  high[ -]performance \
   |  solutions[ -]based \
   |  unmatched \
   |  unparalleled \
   |  unrivalled \
   *<font color="red"><b>BINGO!</b></font> \
   *igx

   The x option in this job turns on extended syntax, and allows for e.g. the
   liberal use of (non-interpreted!) whitespace for nicer formatting.

   You get the idea?

   --------------------------------------------------------------------------

  9.2. The Pre-defined Filters

   The distribution default.filter file contains a selection of pre-defined
   filters for your convenience:

   js-annoyances

           The purpose of this filter is to get rid of particularly annoying
           JavaScript abuse. To that end, it

              * replaces JavaScript references to the browser's referrer
                information with the string "Not Your Business!". This
                compliments the hide-referrer action on the content level.

              * removes the bindings to the DOM's unload event which we feel
                has no right to exist and is responsible for most "exit
                consoles", i.e. nasty windows that pop up when you close
                another one.

              * removes code that causes new windows to be opened with
                undesired properties, such as being full-screen,
                non-resizeable, without location, status or menu bar etc.

           Use with caution. This is an aggressive filter, and can break
           sites that rely heavily on JavaScript.

   js-events

           This is a very radical measure. It removes virtually all
           JavaScript event bindings, which means that scripts can not react
           to user actions such as mouse movements or clicks, window resizing
           etc, anymore. Use with caution!

           We strongly discourage using this filter as a default since it
           breaks many legitimate scripts. It is meant for use only on
           extra-nasty sites (should you really need to go there).

   html-annoyances

           This filter will undo many common instances of HTML based abuse.

           The BLINK and MARQUEE tags are neutralized (yeah baby!), and
           browser windows will be created as resizeable (as of course they
           should be!), and will have location, scroll and menu bars -- even
           if specified otherwise.

   content-cookies

           Most cookies are set in the HTTP dialog, where they can be
           intercepted by the crunch-incoming-cookies and
           crunch-outgoing-cookies actions. But web sites increasingly make
           use of HTML meta tags and JavaScript to sneak cookies to the
           browser on the content level.

           This filter disables most HTML and JavaScript code that reads or
           sets cookies. It cannot detect all clever uses of these types of
           code, so it should not be relied on as an absolute fix. Use it
           wherever you would also use the cookie crunch actions.

   refresh tags

           Disable any refresh tags if the interval is greater than nine
           seconds (so that redirections done via refresh tags are not
           destroyed). This is useful for dial-on-demand setups, or for those
           who find this HTML feature annoying.

   unsolicited-popups

           This filter attempts to prevent only "unsolicited" pop-up windows
           from opening, yet still allow pop-up windows that the user has
           explicitly chosen to open. It was added in version 3.0.1, as an
           improvement over earlier such filters.

           Technical note: The filter works by redefining the window.open
           JavaScript function to a dummy function, PrivoxyWindowOpen(),
           during the loading and rendering phase of each HTML page access,
           and restoring the function afterward.

           This is recommended only for browsers that cannot perform this
           function reliably themselves. And be aware that some sites require
           such windows in order to function normally. Use with caution.

   all-popups

           Attempt to prevent all pop-up windows from opening. Note this
           should be used with even more discretion than the above, since it
           is more likely to break some sites that require pop-ups for normal
           usage. Use with caution.

   img-reorder

           This is a helper filter that has no value if used alone. It makes
           the banners-by-size and banners-by-link (see below) filters more
           effective and should be enabled together with them.

   banners-by-size

           This filter removes image tags purely based on what size they are.
           Fortunately for us, many ads and banner images tend to conform to
           certain standardized sizes, which makes this filter quite
           effective for ad stripping purposes.

           Occasionally this filter will cause false positives on images that
           are not ads, but just happen to be of one of the standard banner
           sizes.

           Recommended only for those who require extreme ad blocking. The
           default block rules should catch 95+% of all ads without this
           filter enabled.

   banners-by-link

           This is an experimental filter that attempts to kill any banners
           if their URLs seem to point to known or suspected click trackers.
           It is currently not of much value and is not recommended for use
           by default.

   webbugs

           Webbugs are small, invisible images (technically 1X1 GIF images),
           that are used to track users across websites, and collect
           information on them. As an HTML page is loaded by the browser, an
           embedded image tag causes the browser to contact a third-party
           site, disclosing the tracking information through the requested
           URL and/or cookies for that third-party domain, without the user
           ever becoming aware of the interaction with the third-party site.
           HTML-ized spam also uses a similar technique to verify email
           addresses.

           This filter removes the HTML code that loads such "webbugs".

   tiny-textforms

           A rather special-purpose filter that can be used to enlarge
           textareas (those multi-line text boxes in web forms) and turn off
           hard word wrap in them. It was written for the sourceforge.net
           tracker system where such boxes are a nuisance, but it can be
           handy on other sites, too.

           It is not recommended to use this filter as a default.

   jumping-windows

           Many consider windows that move, or resize themselves to be
           abusive. This filter neutralizes the related JavaScript code. Note
           that some sites might not display or behave as intended when using
           this filter. Use with caution.

   frameset-borders

           Some web designers seem to assume that everyone in the world will
           view their web sites using the same browser brand and version,
           screen resolution etc, because only that assumption could explain
           why they'd use static frame sizes, yet prevent their frames from
           being resized by the user, should they be too small to show their
           whole content.

           This filter removes the related HTML code. It should only be
           applied to sites which need it.

   demoronizer

           Many Microsoft products that generate HTML use non-standard
           extensions (read: violations) of the ISO 8859-1 aka Latin-1
           character set. This can cause those HTML documents to display with
           errors on standard-compliant platforms.

           This filter translates the MS-only characters into Latin-1
           equivalents. It is not necessary when using MS products, and will
           cause corruption of all documents that use 8-bit character sets
           other than Latin-1. It's mostly worthwhile for Europeans on non-MS
           platforms, if weird garbage characters sometimes appear on some
           pages, or user agents that don't correct for this on the fly.

   shockwave-flash

           A filter for shockwave haters. As the name suggests, this filter
           strips code out of web pages that is used to embed shockwave flash
           objects.

   quicktime-kioskmode

           Change HTML code that embeds Quicktime objects so that kioskmode,
           which prevents saving, is disabled.

   fun

           Text replacements for subversive browsing fun. Make fun of your
           favorite Monopolist or play buzzword bingo.

   crude-parental

           A demonstration-only filter that shows how Privoxy can be used to
           delete web content on a keyword basis.

   ie-exploits

           An experimental collection of text replacements to disable
           malicious HTML and JavaScript code that exploits known security
           holes in Internet Explorer.

           Presently, it only protects against Nimda and a cross-site
           scripting bug, and would need active maintenance to provide more
           substantial protection.

   site-specifics

           Some web sites have very specific problems, the cure for which
           doesn't apply anywhere else, or could even cause damage on other
           sites.

           This is a collection of such site-specific cures which should only
           be applied to the sites they were intended for, which is what the
           supplied default.action file does. Users shouldn't need to change
           anything regarding this filter.

   google

           A CSS based block for Google text ads. Also removes a width
           limitation and the toolbar advertisement.

   yahoo

           Another CSS based block, this time for Yahoo text ads. And removes
           a width limitation as well.

   msn

           Another CSS based block, this time for MSN text ads. And removes
           tracking URLs, as well as a width limitation.

   blogspot

           Cleans up some Blogspot blogs. Read the fine print before using
           this one!

           This filter also intentionally removes some navigation stuff and
           sets the page width to 100%. As a result, some rounded "corners"
           would appear to early or not at all and as fixing this would
           require a browser that understands background-size (CSS3), they
           are removed instead.

   xml-to-html

           Server-header filter to change the Content-Type from xml to html.

   html-to-xml

           Server-header filter to change the Content-Type from html to xml.

   no-ping

           Removes the non-standard ping attribute from anchor and area HTML
           tags.

   hide-tor-exit-notation

           Client-header filter to remove the Tor exit node notation found in
           Host and Referer headers.

           If Privoxy and Tor are chained and Privoxy is configured to use
           socks4a, one can use "http://www.example.org.foobar.exit/" to
           access the host "www.example.org" through the Tor exit node
           "foobar".

           As the HTTP client isn't aware of this notation, it treats the
           whole string "www.example.org.foobar.exit" as host and uses it for
           the "Host" and "Referer" headers. From the server's point of view
           the resulting headers are invalid and can cause problems.

           An invalid "Referer" header can trigger "hot-linking" protections,
           an invalid "Host" header will make it impossible for the server to
           find the right vhost (several domains hosted on the same IP
           address).

           This client-header filter removes the "foo.exit" part in those
           headers to prevent the mentioned problems. Note that it only
           modifies the HTTP headers, it doesn't make it impossible for the
           server to detect your Tor exit node based on the IP address the
           request is coming from.

   --------------------------------------------------------------------------

10. Privoxy's Template Files

   All Privoxy built-in pages, i.e. error pages such as the "404 - No Such
   Domain" error page, the "BLOCKED" page and all pages of its web-based user
   interface, are generated from templates. (Privoxy must be running for the
   above links to work as intended.)

   These templates are stored in a subdirectory of the configuration
   directory called templates. On Unixish platforms, this is typically
   /etc/privoxy/templates/.

   The templates are basically normal HTML files, but with place-holders
   (called symbols or exports), which Privoxy fills at run time. It is
   possible to edit the templates with a normal text editor, should you want
   to customize them. (Not recommended for the casual user). Should you
   create your own custom templates, you should use the config setting
   templdir to specify an alternate location, so your templates do not get
   overwritten during upgrades.

   Note that just like in configuration files, lines starting with # are
   ignored when the templates are filled in.

   The place-holders are of the form @name@, and you will find a list of
   available symbols, which vary from template to template, in the comments
   at the start of each file. Note that these comments are not always
   accurate, and that it's probably best to look at the existing HTML code to
   find out which symbols are supported and what they are filled in with.

   A special application of this substitution mechanism is to make whole
   blocks of HTML code disappear when a specific symbol is set. We use this
   for many purposes, one of them being to include the beta warning in all
   our user interface (CGI) pages when Privoxy is in an alpha or beta
   development stage:

   <!-- @if-unstable-start -->

     ... beta warning HTML code goes here ...

   <!-- if-unstable-end@ -->

   If the "unstable" symbol is set, everything in between and including
   @if-unstable-start and if-unstable-end@ will disappear, leaving nothing
   but an empty comment:

   <!--  -->

   There's also an if-then-else construct and an #include mechanism, but
   you'll sure find out if you are inclined to edit the templates ;-)

   All templates refer to a style located at
   http://config.privoxy.org/send-stylesheet. This is, of course, locally
   served by Privoxy and the source for it can be found and edited in the
   cgi-style.css template.

   --------------------------------------------------------------------------

11. Contacting the Developers, Bug Reporting and Feature Requests

   We value your feedback. In fact, we rely on it to improve Privoxy and its
   configuration. However, please note the following hints, so we can provide
   you with the best support:

   --------------------------------------------------------------------------

  11.1. Get Support

   For casual users, our support forum at SourceForge is probably best
   suited: http://sourceforge.net/tracker/?group_id=11118&atid=211118

   All users are of course welcome to discuss their issues on the users
   mailing list, where the developers also hang around.

   Note that the Privoxy mailing lists are moderated. Posts from unsubscribed
   addresses have to be accepted manually by a moderator. This may cause a
   delay of several days and if you use a subject that doesn't clearly
   mention Privoxy or one of its features, your message may be accidentally
   discarded as spam.

   If you aren't subscribed, you should therefore spend a few seconds to come
   up with a proper subject. Additionally you should make it clear that you
   want to get CC'd. Otherwise some responses will be directed to the mailing
   list only, and you won't see them.

   --------------------------------------------------------------------------

  11.2. Reporting Problems

   "Problems" for our purposes, come in two forms:

     * Configuration issues, such as ads that slip through, or sites that
       don't function properly due to one Privoxy "action" or another being
       turned "on".

     * "Bugs" in the programming code that makes up Privoxy, such as that
       might cause a crash.

   --------------------------------------------------------------------------

    11.2.1. Reporting Ads or Other Configuration Problems

   Please send feedback on ads that slipped through, innocent images that
   were blocked, sites that don't work properly, and other configuration
   related problem of default.action file, to
   http://sourceforge.net/tracker/?group_id=11118&atid=460288, the Actions
   File Tracker.

   New, improved default.action files may occasionally be made available
   based on your feedback. These will be announced on the ijbswa-announce
   list and available from our the files section of our project page.

   --------------------------------------------------------------------------

    11.2.2. Reporting Bugs

   Please report all bugs through our bug tracker:
   http://sourceforge.net/tracker/?group_id=11118&atid=111118.

   Before doing so, please make sure that the bug has not already been
   submitted and observe the additional hints at the top of the submit form.
   If already submitted, please feel free to add any info to the original
   report that might help to solve the issue.

   Please try to verify that it is a Privoxy bug, and not a browser or site
   bug or documented behaviour that just happens to be different than what
   you expected. If unsure, try toggling off Privoxy, and see if the problem
   persists.

   If you are using your own custom configuration, please try the stock
   configs to see if the problem is configuration related. If you're having
   problems with a feature that is disabled by default, please ask around on
   the mailing list if others can reproduce the problem.

   If you aren't using the latest Privoxy version, the bug may have been
   found and fixed in the meantime. We would appreciate if you could take the
   time to upgrade to the latest version (or even the latest CVS snapshot)
   and verify that your bug still exists.

   Please be sure to provide the following information:

     * The exact Privoxy version you are using (if you got the source from
       CVS, please also provide the source code revisions as shown in
       http://config.privoxy.org/show-version).

     * The operating system and versions you run Privoxy on, (e.g. Windows XP
       SP2), if you are using a Unix flavor, sending the output of "uname -a"
       should do, in case of GNU/Linux, please also name the distribution.

     * The name, platform, and version of the browser you were using (e.g.
       Internet Explorer v5.5 for Mac).

     * The URL where the problem occurred, or some way for us to duplicate
       the problem (e.g. http://somesite.example.com/?somethingelse=123).

     * Whether your version of Privoxy is one supplied by the Privoxy
       developers via SourceForge, or if you got your copy somewhere else.

     * Whether you are using Privoxy in tandem with another proxy such as
       Tor. If so, please temporary disable the other proxy to see if the
       symptoms change.

     * Whether you are using a personal firewall product. If so, does Privoxy
       work without it?

     * Any other pertinent information to help identify the problem such as
       config or log file excerpts (yes, you should have log file entries for
       each action taken).

   You don't have to tell us your actual name when filing a problem report,
   but please use a nickname so we can differentiate between your messages
   and the ones entered by other "anonymous" users that may respond to your
   request if they have the same problem or already found a solution.

   Please also check the status of your request a few days after submitting
   it, as we may request additional information. If you use a SF id, you
   should automatically get a mail when someone responds to your request.

   The appendix of the Privoxy User Manual also has helpful information on
   understanding actions, and action debugging.

   --------------------------------------------------------------------------

  11.3. Request New Features

   You are welcome to submit ideas on new features or other proposals for
   improvement through our feature request tracker at
   http://sourceforge.net/tracker/?atid=361118&group_id=11118.

   --------------------------------------------------------------------------

  11.4. Other

   For any other issues, feel free to use the mailing lists. Technically
   interested users and people who wish to contribute to the project are also
   welcome on the developers list! You can find an overview of all
   Privoxy-related mailing lists, including list archives, at:
   http://sourceforge.net/mail/?group_id=11118.

   --------------------------------------------------------------------------

12. Privoxy Copyright, License and History

   Copyright (c) 2001-2008 by Privoxy Developers
   <ijbswa-developers@lists.sourceforge.net>

   Some source code is based on code Copyright (c) 1997 by Anonymous Coders
   and Junkbusters, Inc. and licensed under the GNU General Public License.

   --------------------------------------------------------------------------

  12.1. License

   Privoxy is free software; you can redistribute it and/or modify it under
   the terms of the GNU General Public License, version 2, as published by
   the Free Software Foundation.

   This program is distributed in the hope that it will be useful, but
   WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
   or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
   for more details, which is available from the Free Software Foundation,
   Inc, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA

   You should have received a copy of the GNU General Public License along
   with this program; if not, write to the

    Free Software
    Foundation, Inc. 51 Franklin Street, Fifth Floor
    Boston, MA 02110-1301
    USA

   --------------------------------------------------------------------------

  12.2. History

   A long time ago, there was the Internet Junkbuster, by Anonymous Coders
   and Junkbusters Corporation. This saved many users a lot of pain in the
   early days of web advertising and user tracking.

   But the web, its protocols and standards, and with it, the techniques for
   forcing ads on users, give up autonomy over their browsing, and for
   tracking them, keeps evolving. Unfortunately, the Internet Junkbuster did
   not. Version 2.0.2, published in 1998, was (and is) the last official
   release available from Junkbusters Corporation. Fortunately, it had been
   released under the GNU GPL, which allowed further development by others.

   So Stefan Waldherr started maintaining an improved version of the
   software, to which eventually a number of people contributed patches. It
   could already replace banners with a transparent image, and had a first
   version of pop-up killing, but it was still very closely based on the
   original, with all its limitations, such as the lack of HTTP/1.1 support,
   flexible per-site configuration, or content modification. The last release
   from this effort was version 2.0.2-10, published in 2000.

   Then, some developers picked up the thread, and started turning the
   software inside out, upside down, and then reassembled it, adding many new
   features along the way.

   The result of this is Privoxy, whose first stable version, 3.0, was
   released August, 2002.

   --------------------------------------------------------------------------

  12.3. Authors

   Current Privoxy Team:

    Fabian Keil, lead developer
    David Schmidt, developer

    Hal Burgiss
    Gerry Murphy
    Roland Rosenfeld
    Jrg Strohmayer

   Former Privoxy Team Members:

    Johny Agotnes
    Rodrigo Barbosa
    Moritz Barsnick
    Ian Cummings
    Brian Dessent
    Jon Foster
    Karsten Hopp
    Alexander Lazic
    Daniel Leite
    Gbor Liptk
    Adam Lock
    Guy Laroche
    Mark Martinec
    Justin McMurtry
    Andreas Oesterhelt
    Haroon Rafique
    Georg Sauthoff
    Thomas Steudten
    Rodney Stromlund
    Sviatoslav Sviridov
    Sarantis Paskalis
    Stefan Waldherr

   Thanks to the many people who have tested Privoxy, reported bugs, provided
   patches, made suggestions or contributed in some way. These include (in
   alphabetical order):

    Ken Arromdee
    Devin Bayer
    Gergely Bor
    Reiner Buehl
    Andrew J. Caines
    Clifford Caoile
    Frdric Crozat 
    Michael T. Davis
    Mattes Dolak
    Peter E.
    Florian Effenberger
    Markus Elfring
    Dean Gaudet
    Stephen Gildea
    Daniel Griscom
    Felix Grbert
    Aaron Hamid
    Darel Henman
    Magnus Holmgren
    Ralf Horstmann
    Stefan Huehner
    Peter Hyman
    Derek Jennings
    Petr Kadlec
    David Laight
    Bert van Leeuwen
    Don Libes
    Paul Lieverse
    Toby Lyward
    Wil Mahan
    Jindrich Makovicka
    David Mediavilla
    Raphael Moll
    Amuro Namie
    Adam Piggott
    Dan Price
    Lee R.
    Roberto Ragusa
    Flix Rauch
    Maynard Riley
    Chung-chieh Shan
    Spinor S.
    Bart Schelstraete
    Oliver Stoeneberg
    Peter Thoenen
    Martin Thomas
    Song Weijia
    Jrg Weinmann
    Darren Wiebe
    Bobby G. Vinyard
    Anduin Withers
    Oliver Yeoh
    Jamie Zawinski

   Privoxy is based in part on code originally developed by Junkbusters Corp.
   and Anonymous Coders.

   Privoxy heavily relies on Philip Hazel's PCRE.

   The code to filter compressed content makes use of zlib which is written
   by Jean-loup Gailly and Mark Adler.

   On systems that lack snprintf(), Privoxy is using a version written by
   Mark Martinec. On systems that lack strptime(), Privoxy is using the one
   from the GNU C Library written by Ulrich Drepper.

   --------------------------------------------------------------------------

13. See Also

   Other references and sites of interest to Privoxy users:

   http://www.privoxy.org/, the Privoxy Home page.

   http://www.privoxy.org/faq/, the Privoxy FAQ.

   http://sourceforge.net/projects/ijbswa/, the Project Page for Privoxy on
   SourceForge.

   http://config.privoxy.org/, the web-based user interface. Privoxy must be
   running for this to work. Shortcut: http://p.p/

   http://sourceforge.net/tracker/?group_id=11118&atid=460288, to submit
   "misses" and other configuration related suggestions to the developers.

   http://www.junkbusters.com/ht/en/cookies.html, an explanation how cookies
   are used to track web users.

   http://www.junkbusters.com/ijb.html, the original Internet Junkbuster.

   http://privacy.net/, a useful site to check what information about you is
   leaked while you browse the web.

   http://www.squid-cache.org/, a popular caching proxy, which is often used
   together with Privoxy.

   http://www.pps.jussieu.fr/~jch/software/polipo/, Polipo is a caching proxy
   with advanced features like pipelining, multiplexing and caching of
   partial instances. In many setups it can be used as Squid replacement.

   http://tor.eff.org/, Tor can help anonymize web browsing, web publishing,
   instant messaging, IRC, SSH, and other applications.

   http://www.privoxy.org/developer-manual/, the Privoxy developer manual.

   --------------------------------------------------------------------------

14. Appendix

  14.1. Regular Expressions

   Privoxy uses Perl-style "regular expressions" in its actions files and
   filter file, through the PCRE and PCRS libraries.

   If you are reading this, you probably don't understand what "regular
   expressions" are, or what they can do. So this will be a very brief
   introduction only. A full explanation would require a book ;-)

   Regular expressions provide a language to describe patterns that can be
   run against strings of characters (letter, numbers, etc), to see if they
   match the string or not. The patterns are themselves (sometimes complex)
   strings of literal characters, combined with wild-cards, and other special
   characters, called meta-characters. The "meta-characters" have special
   meanings and are used to build complex patterns to be matched against.
   Perl Compatible Regular Expressions are an especially convenient "dialect"
   of the regular expression language.

   To make a simple analogy, we do something similar when we use wild-card
   characters when listing files with the dir command in DOS. *.* matches all
   filenames. The "special" character here is the asterisk which matches any
   and all characters. We can be more specific and use ? to match just
   individual characters. So "dir file?.text" would match "file1.txt",
   "file2.txt", etc. We are pattern matching, using a similar technique to
   "regular expressions"!

   Regular expressions do essentially the same thing, but are much, much more
   powerful. There are many more "special characters" and ways of building
   complex patterns however. Let's look at a few of the common ones, and then
   some examples:

   . - Matches any single character, e.g. "a", "A", "4", ":", or "@".

   ? - The preceding character or expression is matched ZERO or ONE times.
   Either/or.

   + - The preceding character or expression is matched ONE or MORE times.

   * - The preceding character or expression is matched ZERO or MORE times.

   \ - The "escape" character denotes that the following character should be
   taken literally. This is used where one of the special characters (e.g.
   ".") needs to be taken literally and not as a special meta-character.
   Example: "example\.com", makes sure the period is recognized only as a
   period (and not expanded to its meta-character meaning of any single
   character).

   [ ] - Characters enclosed in brackets will be matched if any of the
   enclosed characters are encountered. For instance, "[0-9]" matches any
   numeric digit (zero through nine). As an example, we can combine this with
   "+" to match any digit one of more times: "[0-9]+".

   ( ) - parentheses are used to group a sub-expression, or multiple
   sub-expressions.

   | - The "bar" character works like an "or" conditional statement. A match
   is successful if the sub-expression on either side of "|" matches. As an
   example: "/(this|that) example/" uses grouping and the bar character and
   would match either "this example" or "that example", and nothing else.

   These are just some of the ones you are likely to use when matching URLs
   with Privoxy, and is a long way from a definitive list. This is enough to
   get us started with a few simple examples which may be more illuminating:

   /.*/banners/.* - A simple example that uses the common combination of "."
   and "*" to denote any character, zero or more times. In other words, any
   string at all. So we start with a literal forward slash, then our regular
   expression pattern (".*") another literal forward slash, the string
   "banners", another forward slash, and lastly another ".*". We are building
   a directory path here. This will match any file with the path that has a
   directory named "banners" in it. The ".*" matches any characters, and this
   could conceivably be more forward slashes, so it might expand into a much
   longer looking path. For example, this could match:
   "/eye/hate/spammers/banners/annoy_me_please.gif", or just
   "/banners/annoying.html", or almost an infinite number of other possible
   combinations, just so it has "banners" in the path somewhere.

   And now something a little more complex:

   /.*/adv((er)?ts?|ertis(ing|ements?))?/ - We have several literal forward
   slashes again ("/"), so we are building another expression that is a file
   path statement. We have another ".*", so we are matching against any
   conceivable sub-path, just so it matches our expression. The only true
   literal that must match our pattern is adv, together with the forward
   slashes. What comes after the "adv" string is the interesting part.

   Remember the "?" means the preceding expression (either a literal
   character or anything grouped with "(...)" in this case) can exist or not,
   since this means either zero or one match. So
   "((er)?ts?|ertis(ing|ements?))" is optional, as are the individual
   sub-expressions: "(er)", "(ing|ements?)", and the "s". The "|" means "or".
   We have two of those. For instance, "(ing|ements?)", can expand to match
   either "ing" OR "ements?". What is being done here, is an attempt at
   matching as many variations of "advertisement", and similar, as possible.
   So this would expand to match just "adv", or "advert", or "adverts", or
   "advertising", or "advertisement", or "advertisements". You get the idea.
   But it would not match "advertizements" (with a "z"). We could fix that by
   changing our regular expression to:
   "/.*/adv((er)?ts?|erti(s|z)(ing|ements?))?/", which would then match
   either spelling.

   /.*/advert[0-9]+\.(gif|jpe?g) - Again another path statement with forward
   slashes. Anything in the square brackets "[ ]" can be matched. This is
   using "0-9" as a shorthand expression to mean any digit one through nine.
   It is the same as saying "0123456789". So any digit matches. The "+" means
   one or more of the preceding expression must be included. The preceding
   expression here is what is in the square brackets -- in this case, any
   digit one through nine. Then, at the end, we have a grouping:
   "(gif|jpe?g)". This includes a "|", so this needs to match the expression
   on either side of that bar character also. A simple "gif" on one side, and
   the other side will in turn match either "jpeg" or "jpg", since the "?"
   means the letter "e" is optional and can be matched once or not at all. So
   we are building an expression here to match image GIF or JPEG type image
   file. It must include the literal string "advert", then one or more
   digits, and a "." (which is now a literal, and not a special character,
   since it is escaped with "\"), and lastly either "gif", or "jpeg", or
   "jpg". Some possible matches would include: "//advert1.jpg",
   "/nasty/ads/advert1234.gif", "/banners/from/hell/advert99.jpg". It would
   not match "advert1.gif" (no leading slash), or "/adverts232.jpg" (the
   expression does not include an "s"), or "/advert1.jsp" ("jsp" is not in
   the expression anywhere).

   We are barely scratching the surface of regular expressions here so that
   you can understand the default Privoxy configuration files, and maybe use
   this knowledge to customize your own installation. There is much, much
   more that can be done with regular expressions. Now that you know enough
   to get started, you can learn more on your own :/

   More reading on Perl Compatible Regular expressions:
   http://perldoc.perl.org/perlre.html

   For information on regular expression based substitutions and their
   applications in filters, please see the filter file tutorial in this
   manual.

   --------------------------------------------------------------------------

  14.2. Privoxy's Internal Pages

   Since Privoxy proxies each requested web page, it is easy for Privoxy to
   trap certain special URLs. In this way, we can talk directly to Privoxy,
   and see how it is configured, see how our rules are being applied, change
   these rules and other configuration options, and even turn Privoxy's
   filtering off, all with a web browser.

   The URLs listed below are the special ones that allow direct access to
   Privoxy. Of course, Privoxy must be running to access these. If not, you
   will get a friendly error message. Internet access is not necessary
   either.

     * Privoxy main page:

         http://config.privoxy.org/

       There is a shortcut: http://p.p/ (But it doesn't provide a fall-back
       to a real page, in case the request is not sent through Privoxy)

     * Show information about the current configuration, including viewing
       and editing of actions files:

         http://config.privoxy.org/show-status

     * Show the source code version numbers:

         http://config.privoxy.org/show-version

     * Show the browser's request headers:

         http://config.privoxy.org/show-request

     * Show which actions apply to a URL and why:

         http://config.privoxy.org/show-url-info

     * Toggle Privoxy on or off. This feature can be turned off/on in the
       main config file. When toggled "off", "Privoxy" continues to run, but
       only as a pass-through proxy, with no actions taking place:

         http://config.privoxy.org/toggle

       Short cuts. Turn off, then on:

         http://config.privoxy.org/toggle?set=disable

         http://config.privoxy.org/toggle?set=enable

   These may be bookmarked for quick reference. See next.

   --------------------------------------------------------------------------

    14.2.1. Bookmarklets

   Below are some "bookmarklets" to allow you to easily access a "mini"
   version of some of Privoxy's special pages. They are designed for MS
   Internet Explorer, but should work equally well in Netscape, Mozilla, and
   other browsers which support JavaScript. They are designed to run directly
   from your bookmarks - not by clicking the links below (although that
   should work for testing).

   To save them, right-click the link and choose "Add to Favorites" (IE) or
   "Add Bookmark" (Netscape). You will get a warning that the bookmark "may
   not be safe" - just click OK. Then you can run the Bookmarklet directly
   from your favorites/bookmarks. For even faster access, you can put them on
   the "Links" bar (IE) or the "Personal Toolbar" (Netscape), and run them
   with a single click.

     * Privoxy - Enable

     * Privoxy - Disable

     * Privoxy - Toggle Privoxy (Toggles between enabled and disabled)

     * Privoxy- View Status

     * Privoxy - Why?

   Credit: The site which gave us the general idea for these bookmarklets is
   www.bookmarklets.com. They have more information about bookmarklets.

   --------------------------------------------------------------------------

  14.3. Chain of Events

   Let's take a quick look at how some of Privoxy's core features are
   triggered, and the ensuing sequence of events when a web page is requested
   by your browser:

     * First, your web browser requests a web page. The browser knows to send
       the request to Privoxy, which will in turn, relay the request to the
       remote web server after passing the following tests:

     * Privoxy traps any request for its own internal CGI pages (e.g
       http://p.p/) and sends the CGI page back to the browser.

     * Next, Privoxy checks to see if the URL matches any "+block" patterns.
       If so, the URL is then blocked, and the remote web server will not be
       contacted. "+handle-as-image" and "+handle-as-empty-document" are then
       checked, and if there is no match, an HTML "BLOCKED" page is sent back
       to the browser. Otherwise, if it does match, an image is returned for
       the former, and an empty text document for the latter. The type of
       image would depend on the setting of "+set-image-blocker" (blank,
       checkerboard pattern, or an HTTP redirect to an image elsewhere).

     * Untrusted URLs are blocked. If URLs are being added to the trust file,
       then that is done.

     * If the URL pattern matches the "+fast-redirects" action, it is then
       processed. Unwanted parts of the requested URL are stripped.

     * Now the rest of the client browser's request headers are processed. If
       any of these match any of the relevant actions (e.g.
       "+hide-user-agent", etc.), headers are suppressed or forged as
       determined by these actions and their parameters.

     * Now the web server starts sending its response back (i.e. typically a
       web page).

     * First, the server headers are read and processed to determine, among
       other things, the MIME type (document type) and encoding. The headers
       are then filtered as determined by the "+crunch-incoming-cookies",
       "+session-cookies-only", and "+downgrade-http-version" actions.

     * If the "+kill-popups" action applies, and it is an HTML or JavaScript
       document, the popup-code in the response is filtered on-the-fly as it
       is received.

     * If any "+filter" action or "+deanimate-gifs" action applies (and the
       document type fits the action), the rest of the page is read into
       memory (up to a configurable limit). Then the filter rules (from
       default.filter and any other filter files) are processed against the
       buffered content. Filters are applied in the order they are specified
       in one of the filter files. Animated GIFs, if present, are reduced to
       either the first or last frame, depending on the action setting.The
       entire page, which is now filtered, is then sent by Privoxy back to
       your browser.

       If neither a "+filter" action or "+deanimate-gifs" matches, then
       Privoxy passes the raw data through to the client browser as it
       becomes available.

     * As the browser receives the now (possibly filtered) page content, it
       reads and then requests any URLs that may be embedded within the page
       source, e.g. ad images, stylesheets, JavaScript, other HTML documents
       (e.g. frames), sounds, etc. For each of these objects, the browser
       issues a separate request (this is easily viewable in Privoxy's logs).
       And each such request is in turn processed just as above. Note that a
       complex web page will have many, many such embedded URLs. If these
       secondary requests are to a different server, then quite possibly a
       very differing set of actions is triggered.

   NOTE: This is somewhat of a simplistic overview of what happens with each
   URL request. For the sake of brevity and simplicity, we have focused on
   Privoxy's core features only.

   --------------------------------------------------------------------------

  14.4. Troubleshooting: Anatomy of an Action

   The way Privoxy applies actions and filters to any given URL can be
   complex, and not always so easy to understand what is happening. And
   sometimes we need to be able to see just what Privoxy is doing.
   Especially, if something Privoxy is doing is causing us a problem
   inadvertently. It can be a little daunting to look at the actions and
   filters files themselves, since they tend to be filled with regular
   expressions whose consequences are not always so obvious.

   One quick test to see if Privoxy is causing a problem or not, is to
   disable it temporarily. This should be the first troubleshooting step. See
   the Bookmarklets section on a quick and easy way to do this (be sure to
   flush caches afterward!). Looking at the logs is a good idea too. (Note
   that both the toggle feature and logging are enabled via config file
   settings, and may need to be turned "on".)

   Another easy troubleshooting step to try is if you have done any
   customization of your installation, revert back to the installed defaults
   and see if that helps. There are times the developers get complaints about
   one thing or another, and the problem is more related to a customized
   configuration issue.

   Privoxy also provides the http://config.privoxy.org/show-url-info page
   that can show us very specifically how actions are being applied to any
   given URL. This is a big help for troubleshooting.

   First, enter one URL (or partial URL) at the prompt, and then Privoxy will
   tell us how the current configuration will handle it. This will not help
   with filtering effects (i.e. the "+filter" action) from one of the filter
   files since this is handled very differently and not so easy to trap! It
   also will not tell you about any other URLs that may be embedded within
   the URL you are testing. For instance, images such as ads are expressed as
   URLs within the raw page source of HTML pages. So you will only get info
   for the actual URL that is pasted into the prompt area -- not any
   sub-URLs. If you want to know about embedded URLs like ads, you will have
   to dig those out of the HTML source. Use your browser's "View Page Source"
   option for this. Or right click on the ad, and grab the URL.

   Let's try an example, google.com, and look at it one section at a time in
   a sample configuration (your real configuration may vary):

    Matches for http://www.google.com:

    In file: default.action [ View ] [ Edit ]

    {+deanimate-gifs {last}
    +fast-redirects {check-decoded-url}
    +filter {refresh-tags}
    +filter {img-reorder}
    +filter {banners-by-size}
    +filter {webbugs}
    +filter {jumping-windows}
    +filter {ie-exploits}
    +hide-forwarded-for-headers
    +hide-from-header {block}
    +hide-referrer {forge}
    +session-cookies-only
    +set-image-blocker {pattern}
   /

    { -session-cookies-only }
    .google.com

    { -fast-redirects }
    .google.com

   In file: user.action [ View ] [ Edit ]
   (no matches in this file)

   This is telling us how we have defined our "actions", and which ones match
   for our test case, "google.com". Displayed is all the actions that are
   available to us. Remember, the + sign denotes "on". - denotes "off". So
   some are "on" here, but many are "off". Each example we try may provide a
   slightly different end result, depending on our configuration directives.

   The first listing is for our default.action file. The large, multi-line
   listing, is how the actions are set to match for all URLs, i.e. our
   default settings. If you look at your "actions" file, this would be the
   section just below the "aliases" section near the top. This will apply to
   all URLs as signified by the single forward slash at the end of the
   listing -- " / ".

   But we have defined additional actions that would be exceptions to these
   general rules, and then we list specific URLs (or patterns) that these
   exceptions would apply to. Last match wins. Just below this then are two
   explicit matches for ".google.com". The first is negating our previous
   cookie setting, which was for "+session-cookies-only" (i.e. not
   persistent). So we will allow persistent cookies for google, at least that
   is how it is in this example. The second turns off any "+fast-redirects"
   action, allowing this to take place unmolested. Note that there is a
   leading dot here -- ".google.com". This will match any hosts and
   sub-domains, in the google.com domain also, such as "www.google.com" or
   "mail.google.com". But it would not match "www.google.de"! So, apparently,
   we have these two actions defined as exceptions to the general rules at
   the top somewhere in the lower part of our default.action file, and
   "google.com" is referenced somewhere in these latter sections.

   Then, for our user.action file, we again have no hits. So there is nothing
   google-specific that we might have added to our own, local configuration.
   If there was, those actions would over-rule any actions from previously
   processed files, such as default.action. user.action typically has the
   last word. This is the best place to put hard and fast exceptions,

   And finally we pull it all together in the bottom section and summarize
   how Privoxy is applying all its "actions" to "google.com":

    Final results:

    -add-header
    -block
    -client-header-filter{hide-tor-exit-notation}
    -content-type-overwrite
    -crunch-client-header
    -crunch-if-none-match
    -crunch-incoming-cookies
    -crunch-outgoing-cookies
    -crunch-server-header
    +deanimate-gifs {last}
    -downgrade-http-version
    -fast-redirects
    -filter {js-events}
    -filter {content-cookies}
    -filter {all-popups}
    -filter {banners-by-link}
    -filter {tiny-textforms}
    -filter {frameset-borders}
    -filter {demoronizer}
    -filter {shockwave-flash}
    -filter {quicktime-kioskmode}
    -filter {fun}
    -filter {crude-parental}
    -filter {site-specifics}
    -filter {js-annoyances}
    -filter {html-annoyances}
    +filter {refresh-tags}
    -filter {unsolicited-popups}
    +filter {img-reorder}
    +filter {banners-by-size}
    +filter {webbugs}
    +filter {jumping-windows}
    +filter {ie-exploits}
    -filter {google}
    -filter {yahoo}
    -filter {msn}
    -filter {blogspot}
    -filter {no-ping}
    -force-text-mode
    -handle-as-empty-document
    -handle-as-image
    -hide-accept-language
    -hide-content-disposition
    +hide-forwarded-for-headers
    +hide-from-header {block}
    -hide-if-modified-since
    +hide-referrer {forge}
    -hide-user-agent
    -inspect-jpegs
    -kill-popups
    -limit-connect
    -overwrite-last-modified
    -prevent-compression
    -redirect
    -send-vanilla-wafer
    -send-wafer
    -server-header-filter{xml-to-html}
    -server-header-filter{html-to-xml}
    -session-cookies-only
    +set-image-blocker {pattern}
    -treat-forbidden-connects-like-blocks

   Notice the only difference here to the previous listing, is to
   "fast-redirects" and "session-cookies-only", which are activated
   specifically for this site in our configuration, and thus show in the
   "Final Results".

   Now another example, "ad.doubleclick.net":

    { +block }
     ad*.

    { +block }
     .ad.

    { +block +handle-as-image }
     .[a-vx-z]*.doubleclick.net

   We'll just show the interesting part here - the explicit matches. It is
   matched three different times. Two "+block" sections, and a "+block
   +handle-as-image", which is the expanded form of one of our aliases that
   had been defined as: "+block-as-image". ("Aliases" are defined in the
   first section of the actions file and typically used to combine more than
   one action.)

   Any one of these would have done the trick and blocked this as an unwanted
   image. This is unnecessarily redundant since the last case effectively
   would also cover the first. No point in taking chances with these guys
   though ;-) Note that if you want an ad or obnoxious URL to be invisible,
   it should be defined as "ad.doubleclick.net" is done here -- as both a
   "+block" and an "+handle-as-image". The custom alias "+block-as-image"
   just simplifies the process and make it more readable.

   One last example. Let's try "http://www.example.net/adsl/HOWTO/". This one
   is giving us problems. We are getting a blank page. Hmmm ...

    Matches for http://www.example.net/adsl/HOWTO/:

    In file: default.action [ View ] [ Edit ]

    {-add-header
     -block
     -client-header-filter{hide-tor-exit-notation}
     -content-type-overwrite
     -crunch-client-header
     -crunch-if-none-match
     -crunch-incoming-cookies
     -crunch-outgoing-cookies
     -crunch-server-header
     +deanimate-gifs
     -downgrade-http-version
     +fast-redirects {check-decoded-url}
     -filter {js-events}
     -filter {content-cookies}
     -filter {all-popups}
     -filter {banners-by-link}
     -filter {tiny-textforms}
     -filter {frameset-borders}
     -filter {demoronizer}
     -filter {shockwave-flash}
     -filter {quicktime-kioskmode}
     -filter {fun}
     -filter {crude-parental}
     -filter {site-specifics}
     -filter {js-annoyances}
     -filter {html-annoyances}
     +filter {refresh-tags}
     -filter {unsolicited-popups}
     +filter {img-reorder}
     +filter {banners-by-size}
     +filter {webbugs}
     +filter {jumping-windows}
     +filter {ie-exploits}
     -filter {google}
     -filter {yahoo}
     -filter {msn}
     -filter {blogspot}
     -filter {no-ping}
     -force-text-mode
     -handle-as-empty-document
     -handle-as-image
     -hide-accept-language
     -hide-content-disposition
     +hide-forwarded-for-headers
     +hide-from-header{block}
     +hide-referer{forge}
     -hide-user-agent
     -inspect-jpegs
     -kill-popups
     -overwrite-last-modified
     +prevent-compression
     -redirect
     -send-vanilla-wafer
     -send-wafer
     -server-header-filter{xml-to-html}
     -server-header-filter{html-to-xml}
     +session-cookies-only
     +set-image-blocker{blank}
     -treat-forbidden-connects-like-blocks }
      /

    { +block +handle-as-image }
     /ads

   Ooops, the "/adsl/" is matching "/ads" in our configuration! But we did
   not want this at all! Now we see why we get the blank page. It is actually
   triggering two different actions here, and the effects are aggregated so
   that the URL is blocked, and Privoxy is told to treat the block as if it
   were an image. But this is, of course, all wrong. We could now add a new
   action below this (or better in our own user.action file) that explicitly
   un blocks ( "{-block}") paths with "adsl" in them (remember, last match in
   the configuration wins). There are various ways to handle such exceptions.
   Example:

    { -block }
     /adsl

   Now the page displays ;-) Remember to flush your browser's caches when
   making these kinds of changes to your configuration to insure that you get
   a freshly delivered page! Or, try using Shift+Reload.

   But now what about a situation where we get no explicit matches like we
   did with:

    { +block +handle-as-image }
    /ads

   That actually was very helpful and pointed us quickly to where the problem
   was. If you don't get this kind of match, then it means one of the default
   rules in the first section of default.action is causing the problem. This
   would require some guesswork, and maybe a little trial and error to
   isolate the offending rule. One likely cause would be one of the "+filter"
   actions. These tend to be harder to troubleshoot. Try adding the URL for
   the site to one of aliases that turn off "+filter":

    { shop }
    .quietpc.com
    .worldpay.com   # for quietpc.com
    .jungle.com
    .scan.co.uk
    .forbes.com

   "{ shop }" is an "alias" that expands to "{ -filter -session-cookies-only
   }". Or you could do your own exception to negate filtering:

    { -filter }
    # Disable ALL filter actions for sites in this section
    .forbes.com
    developer.ibm.com
    localhost

   This would turn off all filtering for these sites. This is best put in
   user.action, for local site exceptions. Note that when a simple domain
   pattern is used by itself (without the subsequent path portion), all
   sub-pages within that domain are included automatically in the scope of
   the action.

   Images that are inexplicably being blocked, may well be hitting the
   "+filter{banners-by-size}" rule, which assumes that images of certain
   sizes are ad banners (works well most of the time since these tend to be
   standardized).

   "{ fragile }" is an alias that disables most actions that are the most
   likely to cause trouble. This can be used as a last resort for problem
   sites.

    { fragile }
    # Handle with care: easy to break
    mail.google.
    mybank.example.com

   Remember to flush caches! Note that the mail.google reference lacks the
   TLD portion (e.g. ".com"). This will effectively match any TLD with google
   in it, such as mail.google.de., just as an example.

   If this still does not work, you will have to go through the remaining
   actions one by one to find which one(s) is causing the problem.
