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<title>Filters</title>

<summary>

<p>This document describes the use of filters in Apache.</p>

</summary>

<section id="filters">

<title>Filters</title>

<related>

<modulelist>

<module>mod_deflate</module>

<module>mod_ext_filter</module>

<module>mod_include</module>

</modulelist>

<directivelist>

<directive module="mod_mime">AddInputFilter</directive>

<directive module="mod_mime">AddOutputFilter</directive>

<directive module="mod_mime">RemoveInputFilter</directive>

<directive module="mod_mime">RemoveOutputFilter</directive>

<directive module="mod_ext_filter">ExtFilterDefine</directive>

<directive module="mod_ext_filter">ExtFilterOptions</directive>

<directive module="core">SetInputFilter</directive>

<directive module="core">SetOutputFilter</directive>

</directivelist>

</related>

<p>A <em>filter</em> is a process that is applied to data that

is sent or received by the server. Data sent by clients to the

server is processed by <em>input filters</em> while data sent

by the server to the client is processed by <em>output

filters</em>. Multiple filters can be applied to the data, and

the order of the filters can be explicitly specified.</p>

<p>Filters are used internally by Apache to perform functions such

as chunking and byte-range request handling. In addition, modules

can provide filters that are selectable using run-time

configuration directives. The set of filters that apply to data

can be manipulated with the

<directive module="core">SetInputFilter</directive>,

<directive module="core">SetOutputFilter</directive>,

<directive module="mod_mime">AddInputFilter</directive>,

<directive module="mod_mime">AddOutputFilter</directive>,

<directive module="mod_mime">RemoveInputFilter</directive>, and

<directive module="mod_mime">RemoveOutputFilter</directive>

directives.</p>

<p>The following user-selectable filters are currently provided

with the Apache HTTP Server distribution.</p>

<dl>

<dt>INCLUDES</dt>

<dd>Server-Side Includes processing by <module>mod_include</module></dd>

<dt>DEFLATE</dt>

<dd>Compress output before sending it to the client using

<module>mod_deflate</module>

</dd>

</dl>

<p>In addition, the module <module>mod_ext_filter</module> allows

for external programs to be defined as filters.</p>

</section>

</manualpage>