+
+-------------------------------------------------------------------------------
+
+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.