docs/manual/mod/mod_expires.html.en - httpd - Git at Google

 <?xml version="1.0" encoding="ISO-8859-1"?>
 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
 <html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!--
         XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
               This file is generated from xml source: DO NOT EDIT
         XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
       -->
 <title>mod_expires - Apache HTTP Server</title>
 <link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" />
 <link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" />
 <link href="../style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" />
 <link href="../images/favicon.ico" rel="shortcut icon" /></head>
 <body>
 <div id="page-header">
 <p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p>
 <p class="apache">Apache HTTP Server Version 2.3</p>
 <img alt="" src="../images/feather.gif" /></div>
 <div class="up"><a href="./"><img title="&lt;-" alt="&lt;-" src="../images/left.gif" /></a></div>
 <div id="path">
 <a href="http://www.apache.org/">Apache</a> &gt; <a href="http://httpd.apache.org/">HTTP Server</a> &gt; <a href="http://httpd.apache.org/docs/">Documentation</a> &gt; <a href="../">Version 2.3</a> &gt; <a href="./">Modules</a></div>
 <div id="page-content">
 <div id="preamble"><h1>Apache Module mod_expires</h1>
 <div class="toplang">
 <p><span>Available Languages: </span><a href="../en/mod/mod_expires.html" title="English">&nbsp;en&nbsp;</a> |
 <a href="../fr/mod/mod_expires.html" hreflang="fr" rel="alternate" title="Français">&nbsp;fr&nbsp;</a> |
 <a href="../ja/mod/mod_expires.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a> |
 <a href="../ko/mod/mod_expires.html" hreflang="ko" rel="alternate" title="Korean">&nbsp;ko&nbsp;</a></p>
 </div>
 <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">Module Identifier:</a></th><td>expires_module</td></tr>
 <tr><th><a href="module-dict.html#SourceFile">Source File:</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 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>

     <p> When the <code>Expires</code> header is already part of the response
     generated by the server, for example when generated by a CGI script or
     proxied from an origin server, this module does not change or add
     an <code>Expires</code> or <code>Cache-Control</code> header.</p>
 </div>
 <div id="quickview"><h3 class="directives">Directives</h3>
 <ul id="toc">
 <li><img alt="" src="../images/down.gif" /> <a href="#expiresactive">ExpiresActive</a></li>
 <li><img alt="" src="../images/down.gif" /> <a href="#expiresbytype">ExpiresByType</a></li>
 <li><img alt="" src="../images/down.gif" /> <a href="#expiresdefault">ExpiresDefault</a></li>
 </ul>
 <h3>Topics</h3>
 <ul id="topics">
 <li><img alt="" src="../images/down.gif" /> <a href="#AltSyn">Alternate Interval Syntax</a></li>
 </ul></div>
 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 <div class="section">
 <h2><a name="AltSyn" id="AltSyn">Alternate Interval Syntax</a></h2>
     <p>The <code class="directive"><a href="#expiresdefault">ExpiresDefault</a></code> and
     <code class="directive"><a href="#expiresbytype">ExpiresByType</a></code> directives
     can also be defined in a more readable syntax of the form:</p>

     <div class="example"><p><code>
       ExpiresDefault "&lt;base&gt; [plus] {&lt;num&gt;
       &lt;type&gt;}*"<br />
       ExpiresByType type/encoding "&lt;base&gt; [plus]
       {&lt;num&gt; &lt;type&gt;}*"
     </code></p></div>

     <p>where &lt;base&gt; is one of:</p>

     <ul>
       <li><code>access</code></li>

       <li><code>now</code> (equivalent to
       '<code>access</code>')</li>

       <li><code>modification</code></li>
     </ul>

     <p>The <code>plus</code> keyword is optional. &lt;num&gt;
     should be an integer value [acceptable to <code>atoi()</code>],
     and &lt;type&gt; is one of:</p>

     <ul>
       <li><code>years</code></li>
       <li><code>months</code></li>
       <li><code>weeks</code></li>
       <li><code>days</code></li>
       <li><code>hours</code></li>
       <li><code>minutes</code></li>
       <li><code>seconds</code></li>
     </ul>

     <p>For example, any of the following directives can be used to
     make documents expire 1 month after being accessed, by
     default:</p>

     <div class="example"><p><code>
       ExpiresDefault "access plus 1 month"<br />
       ExpiresDefault "access plus 4 weeks"<br />
       ExpiresDefault "access plus 30 days"
     </code></p></div>

     <p>The expiry time can be fine-tuned by adding several
     '&lt;num&gt; &lt;type&gt;' clauses:</p>

     <div class="example"><p><code>
       ExpiresByType text/html "access plus 1 month 15
       days 2 hours"<br />
       ExpiresByType image/gif "modification plus 5 hours 3
       minutes"
     </code></p></div>

     <p>Note that if you use a modification date based setting, the
     Expires header will <strong>not</strong> be added to content
     that does not come from a file on disk. This is due to the fact
     that there is no modification time for such content.</p>
 </div>
 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 <div class="directive-section"><h2><a name="ExpiresActive" id="ExpiresActive">ExpiresActive</a> <a name="expiresactive" id="expiresactive">Directive</a></h2>
 <table class="directive">
 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enables generation of <code>Expires</code>
 headers</td></tr>
 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ExpiresActive On|Off</code></td></tr>
 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ExpiresActive Off</code></td></tr>
 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>Indexes</td></tr>
 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 <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> 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>

     <p>Note that this directive does not guarantee that an
     <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>
 <div class="directive-section"><h2><a name="ExpiresByType" id="ExpiresByType">ExpiresByType</a> <a name="expiresbytype" id="expiresbytype">Directive</a></h2>
 <table class="directive">
 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Value of the <code>Expires</code> header configured
 by MIME type</td></tr>
 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ExpiresByType <var>MIME-type</var>
 <var>&lt;code&gt;seconds</var></code></td></tr>
 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>Indexes</td></tr>
 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 <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 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
     should be used is specified by the
     <code><var>&lt;code&gt;</var></code> field; <code>M</code>
     means that the file's last modification time should be used as
     the base time, and <code>A</code> means the client's access
     time should be used.</p>

     <p>The difference in effect is subtle. If <code>M</code> is used,
     all current copies of the document in all caches will expire at
     the same time, which can be good for something like a weekly
     notice that's always found at the same URL. If <code>A</code> is
     used, the date of expiration is different for each client; this
     can be good for image files that don't change very often,
     particularly for a set of related documents that all refer to
     the same images (<em>i.e.</em>, the images will be accessed
     repeatedly within a relatively short timespan).</p>

     <div class="example"><h3>Example:</h3><p><code>
       # enable expirations<br />
       ExpiresActive On<br />
       # expire GIF images after a month in the client's cache<br />
       ExpiresByType image/gif A2592000<br />
       # HTML documents are good for a week from the<br />
       # time they were changed<br />
       ExpiresByType text/html M604800
     </code></p></div>

     <p>Note that this directive only has effect if
     <code>ExpiresActive On</code> has been specified. It overrides,
     for the specified MIME type <em>only</em>, any expiration date
     set by the <code class="directive"><a href="#expiresdefault">ExpiresDefault</a></code>
     directive.</p>

     <p>You can also specify the expiration time calculation using
     an <a href="#AltSyn">alternate syntax</a>, described earlier in
     this document.</p>

 </div>
 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 <div class="directive-section"><h2><a name="ExpiresDefault" id="ExpiresDefault">ExpiresDefault</a> <a name="expiresdefault" id="expiresdefault">Directive</a></h2>
 <table class="directive">
 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Default algorithm for calculating expiration time</td></tr>
 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ExpiresDefault <var>&lt;code&gt;seconds</var></code></td></tr>
 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>Indexes</td></tr>
 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_expires</td></tr>
 </table>
     <p>This directive sets the default algorithm for calculating the
     expiration time for all documents in the affected realm. It can be
     overridden on a type-by-type basis by the <code class="directive"><a href="#expiresbytype">ExpiresByType</a></code> directive. See the
     description of that directive for details about the syntax of the
     argument, and the <a href="#AltSyn">alternate syntax</a>
     description as well.</p>

 </div>
 </div>
 <div class="bottomlang">
 <p><span>Available Languages: </span><a href="../en/mod/mod_expires.html" title="English">&nbsp;en&nbsp;</a> |
 <a href="../fr/mod/mod_expires.html" hreflang="fr" rel="alternate" title="Français">&nbsp;fr&nbsp;</a> |
 <a href="../ja/mod/mod_expires.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a> |
 <a href="../ko/mod/mod_expires.html" hreflang="ko" rel="alternate" title="Korean">&nbsp;ko&nbsp;</a></p>
 </div><div id="footer">
 <p class="apache">Copyright 2011 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>
 <p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p></div>
 </body></html>
	<?xml version="1.0" encoding="ISO-8859-1"?>
	<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
	<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!--
	XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
	This file is generated from xml source: DO NOT EDIT
	XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
	-->
	<title>mod_expires - Apache HTTP Server</title>
	<link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" />
	<link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" />
	<link href="../style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" />
	<link href="../images/favicon.ico" rel="shortcut icon" /></head>
	<body>
	<div id="page-header">
	<p class="menu"><a href="../mod/">Modules</a> \| <a href="../mod/directives.html">Directives</a> \| <a href="../faq/">FAQ</a> \| <a href="../glossary.html">Glossary</a> \| <a href="../sitemap.html">Sitemap</a></p>
	<p class="apache">Apache HTTP Server Version 2.3</p>
	<img alt="" src="../images/feather.gif" /></div>
	<div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div>
	<div id="path">
	<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="../">Version 2.3</a> > <a href="./">Modules</a></div>
	<div id="page-content">
	<div id="preamble"><h1>Apache Module mod_expires</h1>
	<div class="toplang">
	<p><span>Available Languages: </span><a href="../en/mod/mod_expires.html" title="English"> en </a> \|
	<a href="../fr/mod/mod_expires.html" hreflang="fr" rel="alternate" title="Français"> fr </a> \|
	<a href="../ja/mod/mod_expires.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> \|
	<a href="../ko/mod/mod_expires.html" hreflang="ko" rel="alternate" title="Korean"> ko </a></p>
	</div>
	<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">Module Identifier:</a></th><td>expires_module</td></tr>
	<tr><th><a href="module-dict.html#SourceFile">Source File:</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 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>

	<p> When the <code>Expires</code> header is already part of the response
	generated by the server, for example when generated by a CGI script or
	proxied from an origin server, this module does not change or add
	an <code>Expires</code> or <code>Cache-Control</code> header.</p>
	</div>
	<div id="quickview"><h3 class="directives">Directives</h3>
	<ul id="toc">
	<li><img alt="" src="../images/down.gif" /> <a href="#expiresactive">ExpiresActive</a></li>
	<li><img alt="" src="../images/down.gif" /> <a href="#expiresbytype">ExpiresByType</a></li>
	<li><img alt="" src="../images/down.gif" /> <a href="#expiresdefault">ExpiresDefault</a></li>
	</ul>
	<h3>Topics</h3>
	<ul id="topics">
	<li><img alt="" src="../images/down.gif" /> <a href="#AltSyn">Alternate Interval Syntax</a></li>
	</ul></div>
	<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
	<div class="section">
	<h2><a name="AltSyn" id="AltSyn">Alternate Interval Syntax</a></h2>
	<p>The <code class="directive"><a href="#expiresdefault">ExpiresDefault</a></code> and
	<code class="directive"><a href="#expiresbytype">ExpiresByType</a></code> directives
	can also be defined in a more readable syntax of the form:</p>

	<div class="example"><p><code>
	ExpiresDefault "<base> [plus] {<num>
	<type>}*"<br />
	ExpiresByType type/encoding "<base> [plus]
	{<num> <type>}*"
	</code></p></div>

	<p>where <base> is one of:</p>

	<ul>
	<li><code>access</code></li>

	<li><code>now</code> (equivalent to
	'<code>access</code>')</li>

	<li><code>modification</code></li>
	</ul>

	<p>The <code>plus</code> keyword is optional. <num>
	should be an integer value [acceptable to <code>atoi()</code>],
	and <type> is one of:</p>

	<ul>
	<li><code>years</code></li>
	<li><code>months</code></li>
	<li><code>weeks</code></li>
	<li><code>days</code></li>
	<li><code>hours</code></li>
	<li><code>minutes</code></li>
	<li><code>seconds</code></li>
	</ul>

	<p>For example, any of the following directives can be used to
	make documents expire 1 month after being accessed, by
	default:</p>

	<div class="example"><p><code>
	ExpiresDefault "access plus 1 month"<br />
	ExpiresDefault "access plus 4 weeks"<br />
	ExpiresDefault "access plus 30 days"
	</code></p></div>

	<p>The expiry time can be fine-tuned by adding several
	'<num> <type>' clauses:</p>

	<div class="example"><p><code>
	ExpiresByType text/html "access plus 1 month 15
	days 2 hours"<br />
	ExpiresByType image/gif "modification plus 5 hours 3
	minutes"
	</code></p></div>

	<p>Note that if you use a modification date based setting, the
	Expires header will <strong>not</strong> be added to content
	that does not come from a file on disk. This is due to the fact
	that there is no modification time for such content.</p>
	</div>
	<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
	<div class="directive-section"><h2><a name="ExpiresActive" id="ExpiresActive">ExpiresActive</a> <a name="expiresactive" id="expiresactive">Directive</a></h2>
	<table class="directive">
	<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enables generation of <code>Expires</code>
	headers</td></tr>
	<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ExpiresActive On\|Off</code></td></tr>
	<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ExpiresActive Off</code></td></tr>
	<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
	<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>Indexes</td></tr>
	<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
	<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> 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>

	<p>Note that this directive does not guarantee that an
	<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>
	<div class="directive-section"><h2><a name="ExpiresByType" id="ExpiresByType">ExpiresByType</a> <a name="expiresbytype" id="expiresbytype">Directive</a></h2>
	<table class="directive">
	<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Value of the <code>Expires</code> header configured
	by MIME type</td></tr>
	<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ExpiresByType <var>MIME-type</var>
	<var><code>seconds</var></code></td></tr>
	<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
	<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>Indexes</td></tr>
	<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
	<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 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
	should be used is specified by the
	<code><var><code></var></code> field; <code>M</code>
	means that the file's last modification time should be used as
	the base time, and <code>A</code> means the client's access
	time should be used.</p>

	<p>The difference in effect is subtle. If <code>M</code> is used,
	all current copies of the document in all caches will expire at
	the same time, which can be good for something like a weekly
	notice that's always found at the same URL. If <code>A</code> is
	used, the date of expiration is different for each client; this
	can be good for image files that don't change very often,
	particularly for a set of related documents that all refer to
	the same images (<em>i.e.</em>, the images will be accessed
	repeatedly within a relatively short timespan).</p>

	<div class="example"><h3>Example:</h3><p><code>
	# enable expirations<br />
	ExpiresActive On<br />
	# expire GIF images after a month in the client's cache<br />
	ExpiresByType image/gif A2592000<br />
	# HTML documents are good for a week from the<br />
	# time they were changed<br />
	ExpiresByType text/html M604800
	</code></p></div>

	<p>Note that this directive only has effect if
	<code>ExpiresActive On</code> has been specified. It overrides,
	for the specified MIME type <em>only</em>, any expiration date
	set by the <code class="directive"><a href="#expiresdefault">ExpiresDefault</a></code>
	directive.</p>

	<p>You can also specify the expiration time calculation using
	an <a href="#AltSyn">alternate syntax</a>, described earlier in
	this document.</p>

	</div>
	<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
	<div class="directive-section"><h2><a name="ExpiresDefault" id="ExpiresDefault">ExpiresDefault</a> <a name="expiresdefault" id="expiresdefault">Directive</a></h2>
	<table class="directive">
	<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Default algorithm for calculating expiration time</td></tr>
	<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ExpiresDefault <var><code>seconds</var></code></td></tr>
	<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
	<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>Indexes</td></tr>
	<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
	<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_expires</td></tr>
	</table>
	<p>This directive sets the default algorithm for calculating the
	expiration time for all documents in the affected realm. It can be
	overridden on a type-by-type basis by the <code class="directive"><a href="#expiresbytype">ExpiresByType</a></code> directive. See the
	description of that directive for details about the syntax of the
	argument, and the <a href="#AltSyn">alternate syntax</a>
	description as well.</p>

	</div>
	</div>
	<div class="bottomlang">
	<p><span>Available Languages: </span><a href="../en/mod/mod_expires.html" title="English"> en </a> \|
	<a href="../fr/mod/mod_expires.html" hreflang="fr" rel="alternate" title="Français"> fr </a> \|
	<a href="../ja/mod/mod_expires.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> \|
	<a href="../ko/mod/mod_expires.html" hreflang="ko" rel="alternate" title="Korean"> ko </a></p>
	</div><div id="footer">
	<p class="apache">Copyright 2011 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>
	<p class="menu"><a href="../mod/">Modules</a> \| <a href="../mod/directives.html">Directives</a> \| <a href="../faq/">FAQ</a> \| <a href="../glossary.html">Glossary</a> \| <a href="../sitemap.html">Sitemap</a></p></div>
	</body></html>