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11 <p>This document describes the use of filters in Apache.</p>
14 <section id="filters">
15 <title>Filters</title>
18 <module>mod_deflate</module>
19 <module>mod_ext_filter</module>
20 <module>mod_include</module>
23 <directive module="mod_mime">AddInputFilter</directive>
24 <directive module="mod_mime">AddOutputFilter</directive>
25 <directive module="mod_ext_filter">ExtFilterDefine</directive>
26 <directive module="mod_ext_filter">ExtFilterOptions</directive>
27 <directive module="core.html">SetInputFilter</directive>
28 <directive module="core.html">SetOutputFilter</directive>
32 <p>A <em>filter</em> is a process that is applied to data that
33 is sent or received by the server. Data sent by clients to the
34 server is processed by <em>input filters</em> while data sent
35 by the server to the client is processed by <em>output
36 filters</em>. Multiple filters can be applied to the data, and
37 the order of the filters can be explicitly specified.</p>
39 <p>Filters are used internally by Apache to perform functions such
40 as chunking and byte-range request handling. In addition, modules
41 can provide filters that are selectable using run-time
42 configuration directives. The set of filters that apply to data
43 can be manipulated with the <directive module="core.html"
44 >SetInputFilter</directive>, <directive module="core.html"
45 >SetOutputFilter</directive>, <directive module="mod_mime"
46 >AddInputFilter</directive>, and <directive module="mod_mime"
47 >AddOutputFilter</directive> directives.</p>
49 <p>The following user-selectable filters are currently provided
50 with the Apache HTTP Server distribution.</p>
54 <dd>Server-Side Includes processing by <module>mod_include</module></dd>
56 <dd>Compress output before sending it to the client using
57 <module>mod_deflate</module></dd>
60 <p>In addition, the module <module>mod_ext_filter</module> allows
61 for external programs to be defined as filters.</p>