Added missing pipe character on line 24.

pages/filters.html

 title=Writing Adblock Plus filters
 
 
 <p>{{s1 Current Adblock Plus versions allow you to "tweak" your filters in many different ways. This document explains the choices that you have and how they can be used.}}</p>
 
   <p>{{s2 <em>Disclaimer</em>: All filter examples given here are really only examples and are not meant to be used.}}</p>
 
   <h2 id="introduction">{{s3 Introduction to Adblock Plus filters}}</h2>
 
   <p>{{s4 The options described in this section should be enough for users who have to create a filter occasionally.}}</p>
 
   <h3 id="basic">{{s5 Basic filter rules}}</h3>
 
   <p>{{s6 The most trivial filter you can define is of course the address of banner you want to block. However, often this address changes every time you open a page. For example it could be <code><fix>http://example.com/ads/banner123.gif</fix></code> where 123 is a random number. Here blocking the complete address won't help you, you need a more general filter — like <code><fix>http://example.com/ads/banner*.gif</fix></code>. Or maybe even <code><fix>http://example.com/ads/*</fix></code>.}}</p>
 
   <p>{{s7 <em>Note</em>: Make sure that you are not replacing too much by wildcards. The filter <code><fix>http://example.com/*</fix></code> will definitely block all banners but it will also block everything else from example.com that you still might want to see.}}</p>
 
   <h3 id="whitelist">{{s8 Defining exception rules}}</h3>
 
   <p>{{s9 Sometimes you will notice that one of your filters that is usually working quite well blocks in some case blocks something that it shouldn't be blocking. You don't want to remove this filter but you still don't want it to match in this one case.}}</p>
 
   <p>{{s10 That's what exception rules are good for — they allow you to define cases where filters shouldn't be applied. For example if you are unhappy with your filter <code><fix>adv</fix></code> blocking <code><fix>http://example.com/advice.html</fix></code>, you can define an exception rule <code><fix>@@advice</fix></code>. Exception rules are no different from filter rules, you can use wildcards or regular expressions. You only have to precede them by <code><fix>@@</fix></code> to indicate an exception rule.}}</p>
 
-  <p>{{s11 Exception rules can do more. If an exception rule starts with http:// or https:// (optionally with a pipe before it) it will make whole pages an exception. For example, if your exception rule is <code><fix>@@|http://example.com</fix></code> and you open some page from example.com — Adblock Plus will be entirely disabled on this page and nothing will be blocked.}}</p>
+  <p>{{s11 Exception rules can do more. If an exception rule starts with http:// or https:// (optionally with a pipe before it) it will make whole pages an exception. For example, if your exception rule is <code><fix>@@||http://example.com</fix></code> and you open some page from example.com — Adblock Plus will be entirely disabled on this page and nothing will be blocked.}}</p>

[Philip Hill, 2015/07/13 13:27:55]

Thanks to Arthur, the great, this is the actually valid filter matching this
sentence's content:
@@||example.com^$document

 
   <h3 id="anchors">{{s12 Matching at beginning/end of an address}}</h3>
 
   <p>{{s13 Usually Adblock Plus treats every filter as if it had a wildcard at its beginning and end, e.g. there is not difference between the filters <code><fix>ad</fix></code> and <code><fix>*ad*</fix></code>. While this is usually unproblematic, sometimes you wish that the filter you defined only matches at the beginning or end of an address. For example you might want to block all Flash, but if you add the filter <code><fix>swf</fix></code> the address <code><fix>http://example.com/swf/index.html</fix></code> will also be blocked.}}</p>
 
   <p>{{s14 Solution to this problem: add a pipe symbol to the filter to show that there should be definitely the end of the address at this point. For example the filter <code><fix>swf|</fix></code> will block <code><fix>http://example.com/annoyingflash.swf</fix></code> but not <code><fix>http://example.com/swf/index.html</fix></code>. And the filter <code>|http://baddomain.example/</code> will block <code>http://baddomain.example/banner.gif</code> but not <code>http://gooddomain.example/analyze?http://baddomain.example</code>.}}</p>
 
   <p id="flexible-anchors">{{s15 Sometimes one wants to block <code><fix>http://example.com/banner.gif</fix></code> as well as <code><fix>https://example.com/banner.gif</fix></code> and <code><fix>http://www.example.com/banner.gif</fix></code>. This can be achieved by putting two pipe symbols in front of the filter which makes sure the filter matches at the beginning of the domain name: <code><fix>||example.com/banner.gif</fix></code> will block all these addresses while not blocking <code>http://badexample.com/banner.gif</code> or <code>http://gooddomain.example/analyze?http://example.com/banner.gif</code> (requires Adblock Plus 1.1 or higher).}}</p>
 
   <h3 id="separators">{{s16 Marking separator characters}}</h3>
@@ skipping 225 matching lines @@
   {{s110 The data used for creating the signature is a concatenated list of request variables (namely URI, host and user agent) separated by the <code><fix>NUL</fix></code> character "\0". For example:}}
 </p>
 
 <pre>
   /index.html?q=foo\0www.example.com\0Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:30.0) Gecko/20100101 Firefox/30.0
 </pre>
 
 <p>
   {{s111 Finally, generate the signature for this string by using the signature algorithm SEC_OID_ISO_SHA_WITH_RSA_SIGNATURE (default when using OpenSSL).}}
 </p>