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    <title>Filters - Apache HTTPD</title>
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    <h1 align="CENTER">Filters</h1>

    <table border="1">
      <tr>
        <td valign="top"><strong>Related Modules</strong><br />
         <br />
         <a href="mod/mod_deflate.html">mod_defalte</a><br />
         <a href="mod/mod_ext_filter.html">mod_ext_filter</a><br />
         <a href="mod/mod_include.html">mod_include</a><br />
         </td>

        <td valign="top"><strong>Related Directives</strong><br />
         <br />
         <a
        href="mod/mod_mime.html#addinputfilter">AddInputFilter</a><br />
         <a
        href="mod/mod_mime.html#addoutputfilter">AddOutputFilter</a><br />
         <a
        href="mod/mod_ext_filter.html#extfilterdefine">ExtFilterDefine</a><br />
         <a
        href="mod/mod_ext_filter.html#extfilteroptions">ExtFilterOptions</a><br />
         <a
        href="mod/core.html#setinputfilter">SetInputFilter</a><br />
         <a
        href="mod/core.html#setoutputfilter">SetOutputFilter</a><br />
         </td>
      </tr>
    </table>

    <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 <code>SetInputFilter</code>,
    <code>SetOutputFilter</code>, <code>AddInputFilter</code>, and
    <code>AddOutputFilter</code> 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 <a
href="mod/mod_include.html">mod_include</a></dd>
<dt>DEFLATE</dt> <dd>Compress output before sending it to
the client using <a href="mod/mod_deflate.html">mod_deflate</a></dd>
</dl>

    <p>In addition, the module <a
    href="mod/mod_ext_filter.html">mod_ext_filter</a> allows
    for external programs to be defined as filters.</p>

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