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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 - pcrs-based 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.
- -Finally Privoxy supports the - external-filter action to - enable external filters - written in proper programming languages.
- -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 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 pcrs-based 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.
+Finally Privoxy supports the external-filter action to enable external filters written in proper programming languages.
+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 +
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" -+ 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 (add ? to quantifiers to turn them - greedy again).
- -The non-standard option letter D (dynamic) - allows to use the variables $host, $origin (the IP address the request - came from), $path, $url and $listen-address (the address on which Privoxy - accepted the client request. Example: 127.0.0.1:8118). They will be - replaced with the value they refer to before the filter is executed.
- -Note that '$' is a bad choice for a delimiter in a dynamic filter as - you might end up with unintended variables if you use a variable name - directly after the delimiter. Variables will be resolved without escaping - anything, therefore you also have to be careful not to chose delimiters - that appear in the replacement text. For example '<' should be save, - while '?' will sooner or later cause conflicts with $url.
- -The non-standard option letter T (trivial) - prevents parsing for backreferences in the substitute. Use it if you want - to include text like '$&' in your substitute without quoting.
- -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.
- +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 (add ? to quantifiers to turn them greedy again).
+The non-standard option letter D (dynamic) allows to use the variables $host, $origin + (the IP address the request came from), $path, $url and $listen-address (the address on which Privoxy accepted the + client request. Example: 127.0.0.1:8118). They will be replaced with the value they refer to before the filter is + executed.
+Note that '$' is a bad choice for a delimiter in a dynamic filter as you might end up with unintended variables + if you use a variable name directly after the delimiter. Variables will be resolved without escaping anything, + therefore you also have to be careful not to chose delimiters that appear in the replacement text. For example + '<' should be save, while '?' will sooner or later cause conflicts with $url.
+The non-standard option letter T (trivial) prevents parsing for backreferences in the + substitute. Use it if you want to include text like '$&' in your substitute without quoting.
+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.
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:
- +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/ -+ 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 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 -+ s/foo/bar/g |
Our complete filter now looks like this:
-
- -FILTER: foo Replace all "foo" with "bar" -s/foo/bar/g -+ 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:
- +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 +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 -+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:
- +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 +# The status bar is for displaying link targets, not pointless blahblah # -s/window\.status\s*=\s*(['"]).*?\1/dUmMy=1/ig -+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.
- +\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 +# Kill OnUnload popups. Yummy. Test: http://www.zdnet.com/zdsubs/yahoo/tree/yfs.html # -s/(<body [^>]*)onunload(.*>)/$1never$2/iU -+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.
- + "http://www.w3.org/TR/2000/REC-DOM-Level-2-Events-20001113/events.html#Events-eventgroupings-htmlevents" target= + "_top">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 +FILTER: fun Fun text replacements # Spice the daily news: # -s/microsoft(?!\.com)/MicroSuck/ig -+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.
- +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) +# Buzzword Bingo (example for extended regex syntax) # s* industry[ -]leading \ | cutting[ -]edge \ @@ -429,464 +267,267 @@ s* industry[ -]leading \ | unparalleled \ | unrivalled \ *<font color="red"><b>BINGO!</b></font> \ -*igx -+*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.
- +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?
The distribution default.filter file - contains a selection of pre-defined filters for your convenience:
- +The distribution default.filter file contains a selection of pre-defined filters for + your convenience:
The purpose of this filter is to get rid of particularly - annoying JavaScript abuse. To that end, it
- +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.
+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.
+ target="_top">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.
+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.
+Use with caution. This is an aggressive filter, and can break sites that rely heavily on JavaScript.
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).
+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).
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.
+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.
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.
+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.
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.
+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.
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.
+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.
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.
+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.
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.
+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.
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.
+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.
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.
+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 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".
+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".
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.
- +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.
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.
+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.
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.
+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.
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.
+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.
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.
+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.
Change HTML code that embeds Quicktime objects so that - kioskmode, which prevents saving, is disabled.
+Change HTML code that embeds Quicktime objects so that kioskmode, which prevents saving, is + disabled.
Text replacements for subversive browsing fun. Make fun of - your favorite Monopolist or play buzzword bingo.
+Text replacements for subversive browsing fun. Make fun of your favorite Monopolist or play buzzword + bingo.
A demonstration-only filter that shows how Privoxy can be used to delete web content on - a keyword basis.
+A demonstration-only filter that shows how Privoxy can be used to + delete web content on a keyword basis.
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.
+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.
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.
+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.
A CSS based block for Google text ads. Also removes a width - limitation and the toolbar advertisement.
+A CSS based block for Google text ads. Also removes a width limitation and the toolbar + advertisement.
Another CSS based block, this time for Yahoo text ads. And - removes a width limitation as well.
+Another CSS based block, this time for Yahoo text ads. And removes a width limitation as well.
Another CSS based block, this time for MSN text ads. And - removes tracking URLs, as well as a width limitation.
+Another CSS based block, this time for MSN text ads. And removes tracking URLs, as well as a width + limitation.
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.
+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.
Server-header filter to change the Content-Type from xml to - html.
+Server-header filter to change the Content-Type from xml to html.
Server-header filter to change the Content-Type from html to - xml.
+Server-header filter to change the Content-Type from html to xml.
Removes the non-standard ping - attribute from anchor and area HTML tags.
+Removes the non-standard ping attribute from anchor and area HTML tags.
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 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.
+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.
External filters are scripts or programs that can modify the content - in case common filters aren't powerful enough.
- -External filters can be written in any language the platform - Privoxy runs on supports.
- +External filters are scripts or programs that can modify the content in case common filters aren't powerful enough.
+External filters can be written in any language the platform Privoxy runs on + supports.
They are controlled with the external-filter action and - have to be defined in the filterfile first.
- -The header looks like any other filter, but instead of pcrs jobs, - external filters contain a single job which can be a program or a shell - script (which may call other scripts or programs).
- -External filters read the content from STDIN and write the rewritten - content to STDOUT. The environment variables PRIVOXY_URL, PRIVOXY_PATH, - PRIVOXY_HOST, PRIVOXY_ORIGIN, PRIVOXY_LISTEN_ADDRESS can be used to get - some details about the client request.
- -Privoxy will temporary store the - content to filter in the temporary-directory.
- + "actions-file.html#EXTERNAL-FILTER">external-filter action and have to be defined in the filterfile first. +The header looks like any other filter, but instead of pcrs jobs, external filters contain a single job which + can be a program or a shell script (which may call other scripts or programs).
+External filters read the content from STDIN and write the rewritten content to STDOUT. The environment + variables PRIVOXY_URL, PRIVOXY_PATH, PRIVOXY_HOST, PRIVOXY_ORIGIN, PRIVOXY_LISTEN_ADDRESS can be used to get some + details about the client request.
+Privoxy will temporary store the content to filter in the temporary-directory.
- -EXTERNAL-FILTER: cat Pointless example filter that doesn't actually modify the content +EXTERNAL-FILTER: cat Pointless example filter that doesn't actually modify the content /bin/cat # Incorrect reimplementation of the filter above in POSIX shell. @@ -908,56 +549,38 @@ EXTERNAL-FILTER: rotate-image Rotate an image by 180 degree. Test filter with li /usr/local/bin/convert - -rotate 180 - EXTERNAL-FILTER: citation-needed Adds a "[citation needed]" tag to an image. The coordinates may need adjustment. -/usr/local/bin/convert - -pointsize 16 -fill white -annotate +17+418 "[citation needed]" - -+/usr/local/bin/convert - -pointsize 16 -fill white -annotate +17+418 "[citation needed]" - |
| Warning |
|
- Currently external filters are executed with Privoxy's privileges! Only use external - filters you understand and trust. +Currently external filters are executed with Privoxy's privileges! + Only use external filters you understand and trust. |
External filters are experimental and the syntax may change in the - future.
+External filters are experimental and the syntax may change in the future.