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<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Generation of <code>Expires</code> HTTP headers according to

user-specified criteria</td></tr>

<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Generation of <code>Expires</code> and

<code>Cache-Control</code> HTTP headers according to user-specified

criteria</td></tr>

<tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr>

<tr><th><a href="module-dict.html#ModuleIdentifier">ModuleIdentifier:</a></th><td>expires_module</td></tr>

<tr><th><a href="module-dict.html#SourceFile">SourceFile:</a></th><td>mod_expires.c</td></tr></table>

<h3>Summary</h3>

    <p>This module controls the setting of the <code>Expires</code>

    HTTP header in server responses. The expiration date can set to

    be relative to either the time the source file was last

    modified, or to the time of the client access.</p>

    <p>The <code>Expires</code> HTTP header is an instruction to

    the client about the document's validity and persistence. If

    cached, the document may be fetched from the cache rather than

    from the source until this time has passed. After that, the

    cache copy is considered "expired" and invalid, and a new copy

    must be obtained from the source.</p>

    HTTP header and the <code>max-age</code> directive of the

    <code>Cache-Control</code> HTTP header in server responses. The

    expiration date can set to be relative to either the time the

    source file was last modified, or to the time of the client

    access.</p>

    <p>These HTTP headers are an instruction to the client about the

    document's validity and persistence. If cached, the document may

    be fetched from the cache rather than from the source until this

    time has passed. After that, the cache copy is considered

    "expired" and invalid, and a new copy must be obtained from the

    source.</p> 

    <p>To modify <code>Cache-Control</code> directives other than

    <code>max-age</code> (see <a href="http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.9">RFC

    2616 section 14.9</a>), you can use the <code class="directive"><a href="../mod/mod_headers.html#header">Header</a></code> directive.</p>

</div>

<div id="quickview"><h3 class="directives">Directives</h3>

<ul id="toc">

<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_expires</td></tr>

</table>

    <p>This directive enables or disables the generation of the

    <code>Expires</code> header for the document realm in question.

    (That is, if found in an <code>.htaccess</code> file, for

    instance, it applies only to documents generated from that

    directory.) If set to <code>Off</code>, no <code>Expires</code> header

    will be generated for any document in the realm (unless overridden at

    a lower level, such as an <code>.htaccess</code> file overriding a

    server config file). If set to <code>On</code>, the header will be

    added to served documents according to the criteria defined by the 

    <code>Expires</code> and <code>Cache-Control</code> headers for

    the document realm in question.  (That is, if found in an

    <code>.htaccess</code> file, for instance, it applies only to

    documents generated from that directory.) If set to

    <code>Off</code>, the headers will not be generated for any

    document in the realm (unless overridden at a lower level, such as

    an <code>.htaccess</code> file overriding a server config

    file). If set to <code>On</code>, the headers will be added to

    served documents according to the criteria defined by the

    <code class="directive"><a href="#expiresbytype">ExpiresByType</a></code> and

    <code class="directive"><a href="#expiresdefault">ExpiresDefault</a></code> directives

    (<em>q.v.</em>).</p>

    <code class="directive"><a href="#expiresdefault">ExpiresDefault</a></code>

    directives (<em>q.v.</em>).</p>

    <p>Note that this directive does not guarantee that an

    <code>Expires</code> header will be generated. If the criteria

    aren't met, no header will be sent, and the effect will be as

    though this directive wasn't even specified.</p>

    <code>Expires</code> or <code>Cache-Control</code> header will be

    generated. If the criteria aren't met, no header will be sent, and

    the effect will be as though this directive wasn't even

    specified.</p>

</div>

<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>

<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_expires</td></tr>

</table>

    <p>This directive defines the value of the <code>Expires</code>

    header generated for documents of the specified type (<em>e.g.</em>,

    <code>text/html</code>). The second argument sets the number of

    seconds that will be added to a base time to construct the expiration

    date.</p>

    header and the <code>max-age</code> directive of the

    <code>Cache-Control</code> header generated for documents of the

    specified type (<em>e.g.</em>, <code>text/html</code>). The second

    argument sets the number of seconds that will be added to a base

    time to construct the expiration date.  The <code>Cache-Control:

    max-age</code> is calculated by subtracting the request time from

    the expiration date and expressing the result in seconds.</p>

    <p>The base time is either the last modification time of the

    file, or the time of the client's access to the document. Which

<?xml version="1.0"?>

<!DOCTYPE modulesynopsis SYSTEM "../style/modulesynopsis.dtd">

<?xml-stylesheet type="text/xsl" href="../style/manual.en.xsl"?>

<!-- $Revision: 1.3.2.4 $ -->

<!-- $Revision: 1.3.2.5 $ -->

<!--

 Copyright 2002-2004 The Apache Software Foundation

<modulesynopsis metafile="mod_expires.xml.meta">

<name>mod_expires</name>

<description>Generation of <code>Expires</code> HTTP headers according to

user-specified criteria</description>

<description>Generation of <code>Expires</code> and

<code>Cache-Control</code> HTTP headers according to user-specified

criteria</description>

<status>Extension</status>

<sourcefile>mod_expires.c</sourcefile>

<identifier>expires_module</identifier>

<summary>

    <p>This module controls the setting of the <code>Expires</code>

    HTTP header in server responses. The expiration date can set to

    be relative to either the time the source file was last

    modified, or to the time of the client access.</p>

    <p>The <code>Expires</code> HTTP header is an instruction to

    the client about the document's validity and persistence. If

    cached, the document may be fetched from the cache rather than

    from the source until this time has passed. After that, the

    cache copy is considered "expired" and invalid, and a new copy

    must be obtained from the source.</p>

    HTTP header and the <code>max-age</code> directive of the

    <code>Cache-Control</code> HTTP header in server responses. The

    expiration date can set to be relative to either the time the

    source file was last modified, or to the time of the client

    access.</p>

    <p>These HTTP headers are an instruction to the client about the

    document's validity and persistence. If cached, the document may

    be fetched from the cache rather than from the source until this

    time has passed. After that, the cache copy is considered

    "expired" and invalid, and a new copy must be obtained from the

    source.</p> 

    <p>To modify <code>Cache-Control</code> directives other than

    <code>max-age</code> (see <a

    href="http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.9">RFC

    2616 section 14.9</a>), you can use the <directive

    module="mod_headers">Header</directive> directive.</p>

</summary>

<section id="AltSyn"><title>Alternate Interval Syntax</title>

<usage>

    <p>This directive enables or disables the generation of the

    <code>Expires</code> header for the document realm in question.

    (That is, if found in an <code>.htaccess</code> file, for

    instance, it applies only to documents generated from that

    directory.) If set to <code>Off</code>, no <code>Expires</code> header

    will be generated for any document in the realm (unless overridden at

    a lower level, such as an <code>.htaccess</code> file overriding a

    server config file). If set to <code>On</code>, the header will be

    added to served documents according to the criteria defined by the 

    <code>Expires</code> and <code>Cache-Control</code> headers for

    the document realm in question.  (That is, if found in an

    <code>.htaccess</code> file, for instance, it applies only to

    documents generated from that directory.) If set to

    <code>Off</code>, the headers will not be generated for any

    document in the realm (unless overridden at a lower level, such as

    an <code>.htaccess</code> file overriding a server config

    file). If set to <code>On</code>, the headers will be added to

    served documents according to the criteria defined by the

    <directive module="mod_expires">ExpiresByType</directive> and

    <directive module="mod_expires">ExpiresDefault</directive> directives

    (<em>q.v.</em>).</p>

    <directive module="mod_expires">ExpiresDefault</directive>

    directives (<em>q.v.</em>).</p>

    <p>Note that this directive does not guarantee that an

    <code>Expires</code> header will be generated. If the criteria

    aren't met, no header will be sent, and the effect will be as

    though this directive wasn't even specified.</p>

    <code>Expires</code> or <code>Cache-Control</code> header will be

    generated. If the criteria aren't met, no header will be sent, and

    the effect will be as though this directive wasn't even

    specified.</p>

 </usage> 

</directivesynopsis>

<usage>

    <p>This directive defines the value of the <code>Expires</code>

    header generated for documents of the specified type (<em>e.g.</em>,

    <code>text/html</code>). The second argument sets the number of

    seconds that will be added to a base time to construct the expiration

    date.</p>

    header and the <code>max-age</code> directive of the

    <code>Cache-Control</code> header generated for documents of the

    specified type (<em>e.g.</em>, <code>text/html</code>). The second

    argument sets the number of seconds that will be added to a base

    time to construct the expiration date.  The <code>Cache-Control:

    max-age</code> is calculated by subtracting the request time from

    the expiration date and expressing the result in seconds.</p>

    <p>The base time is either the last modification time of the

    file, or the time of the client's access to the document. Which