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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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This file is generated from xml source: DO NOT EDIT
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<title>mod_expires - Apache HTTP Server</title>
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<link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" />
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<link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" />
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<link href="../style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" />
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<link href="../images/favicon.ico" rel="shortcut icon" /></head>
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<body>
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<div id="page-header">
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<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>
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<p class="apache">Apache HTTP Server Version 2.3</p>
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<img alt="" src="../images/feather.gif" /></div>
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<div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div>
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<div id="path">
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<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>
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<div id="page-content">
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<div id="preamble"><h1>Apache Module mod_expires</h1>
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<div class="toplang">
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<p><span>Available Languages: </span><a href="../en/mod/mod_expires.html" title="English"> en </a> |
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<a href="../fr/mod/mod_expires.html" hreflang="fr" rel="alternate" title="Français"> fr </a> |
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<a href="../ja/mod/mod_expires.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> |
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<a href="../ko/mod/mod_expires.html" hreflang="ko" rel="alternate" title="Korean"> ko </a></p>
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</div>
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<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Generation of <code>Expires</code> and
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<code>Cache-Control</code> HTTP headers according to user-specified
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criteria</td></tr>
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<tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr>
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<tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>expires_module</td></tr>
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<tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_expires.c</td></tr></table>
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<h3>Summary</h3>
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<p>This module controls the setting of the <code>Expires</code>
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HTTP header and the <code>max-age</code> directive of the
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<code>Cache-Control</code> HTTP header in server responses. The
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expiration date can set to be relative to either the time the
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source file was last modified, or to the time of the client
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access.</p>
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<p>These HTTP headers are an instruction to the client about the
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document's validity and persistence. If cached, the document may
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be fetched from the cache rather than from the source until this
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time has passed. After that, the cache copy is considered
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"expired" and invalid, and a new copy must be obtained from the
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source.</p>
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<p>To modify <code>Cache-Control</code> directives other than
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<code>max-age</code> (see <a href="http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.9">RFC
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2616 section 14.9</a>), you can use the <code class="directive"><a href="../mod/mod_headers.html#header">Header</a></code> directive.</p>
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</div>
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<div id="quickview"><h3 class="directives">Directives</h3>
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<ul id="toc">
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<li><img alt="" src="../images/down.gif" /> <a href="#expiresactive">ExpiresActive</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#expiresbytype">ExpiresByType</a></li>
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<li><img alt="" src="../images/down.gif" /> <a href="#expiresdefault">ExpiresDefault</a></li>
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</ul>
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<h3>Topics</h3>
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<ul id="topics">
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<li><img alt="" src="../images/down.gif" /> <a href="#AltSyn">Alternate Interval Syntax</a></li>
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</ul></div>
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<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="section">
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<h2><a name="AltSyn" id="AltSyn">Alternate Interval Syntax</a></h2>
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<p>The <code class="directive"><a href="#expiresdefault">ExpiresDefault</a></code> and
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<code class="directive"><a href="#expiresbytype">ExpiresByType</a></code> directives
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can also be defined in a more readable syntax of the form:</p>
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<div class="example"><p><code>
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ExpiresDefault "<base> [plus] {<num>
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<type>}*"<br />
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ExpiresByType type/encoding "<base> [plus]
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{<num> <type>}*"
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</code></p></div>
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<p>where <base> is one of:</p>
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<ul>
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<li><code>access</code></li>
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<li><code>now</code> (equivalent to
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'<code>access</code>')</li>
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<li><code>modification</code></li>
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</ul>
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<p>The <code>plus</code> keyword is optional. <num>
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should be an integer value [acceptable to <code>atoi()</code>],
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and <type> is one of:</p>
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<ul>
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<li><code>years</code></li>
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<li><code>months</code></li>
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<li><code>weeks</code></li>
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<li><code>days</code></li>
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<li><code>hours</code></li>
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<li><code>minutes</code></li>
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<li><code>seconds</code></li>
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</ul>
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<p>For example, any of the following directives can be used to
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make documents expire 1 month after being accessed, by
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default:</p>
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<div class="example"><p><code>
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ExpiresDefault "access plus 1 month"<br />
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ExpiresDefault "access plus 4 weeks"<br />
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ExpiresDefault "access plus 30 days"
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</code></p></div>
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<p>The expiry time can be fine-tuned by adding several
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'<num> <type>' clauses:</p>
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<div class="example"><p><code>
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ExpiresByType text/html "access plus 1 month 15
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days 2 hours"<br />
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ExpiresByType image/gif "modification plus 5 hours 3
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minutes"
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</code></p></div>
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<p>Note that if you use a modification date based setting, the
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Expires header will <strong>not</strong> be added to content
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that does not come from a file on disk. This is due to the fact
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that there is no modification time for such content.</p>
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</div>
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<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="directive-section"><h2><a name="ExpiresActive" id="ExpiresActive">ExpiresActive</a> <a name="expiresactive" id="expiresactive">Directive</a></h2>
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<table class="directive">
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<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enables generation of <code>Expires</code>
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headers</td></tr>
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<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ExpiresActive On|Off</code></td></tr>
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<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ExpiresActive Off</code></td></tr>
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<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
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<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>Indexes</td></tr>
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<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
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<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_expires</td></tr>
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</table>
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<p>This directive enables or disables the generation of the
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<code>Expires</code> and <code>Cache-Control</code> headers for
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the document realm in question. (That is, if found in an
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<code>.htaccess</code> file, for instance, it applies only to
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documents generated from that directory.) If set to
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<code>Off</code>, the headers will not be generated for any
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document in the realm (unless overridden at a lower level, such as
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an <code>.htaccess</code> file overriding a server config
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file). If set to <code>On</code>, the headers will be added to
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served documents according to the criteria defined by the
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<code class="directive"><a href="#expiresbytype">ExpiresByType</a></code> and
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<code class="directive"><a href="#expiresdefault">ExpiresDefault</a></code>
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directives (<em>q.v.</em>).</p>
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<p>Note that this directive does not guarantee that an
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<code>Expires</code> or <code>Cache-Control</code> header will be
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generated. If the criteria aren't met, no header will be sent, and
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the effect will be as though this directive wasn't even
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specified.</p>
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</div>
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<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="directive-section"><h2><a name="ExpiresByType" id="ExpiresByType">ExpiresByType</a> <a name="expiresbytype" id="expiresbytype">Directive</a></h2>
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<table class="directive">
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<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Value of the <code>Expires</code> header configured
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by MIME type</td></tr>
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<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ExpiresByType <var>MIME-type</var>
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<var><code>seconds</var></code></td></tr>
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<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
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<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>Indexes</td></tr>
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<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
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<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_expires</td></tr>
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</table>
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<p>This directive defines the value of the <code>Expires</code>
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header and the <code>max-age</code> directive of the
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<code>Cache-Control</code> header generated for documents of the
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specified type (<em>e.g.</em>, <code>text/html</code>). The second
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argument sets the number of seconds that will be added to a base
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time to construct the expiration date. The <code>Cache-Control:
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max-age</code> is calculated by subtracting the request time from
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the expiration date and expressing the result in seconds.</p>
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<p>The base time is either the last modification time of the
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file, or the time of the client's access to the document. Which
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should be used is specified by the
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<code><var><code></var></code> field; <code>M</code>
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means that the file's last modification time should be used as
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the base time, and <code>A</code> means the client's access
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time should be used.</p>
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<p>The difference in effect is subtle. If <code>M</code> is used,
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all current copies of the document in all caches will expire at
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the same time, which can be good for something like a weekly
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notice that's always found at the same URL. If <code>A</code> is
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used, the date of expiration is different for each client; this
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can be good for image files that don't change very often,
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particularly for a set of related documents that all refer to
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the same images (<em>i.e.</em>, the images will be accessed
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repeatedly within a relatively short timespan).</p>
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<div class="example"><h3>Example:</h3><p><code>
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# enable expirations<br />
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ExpiresActive On<br />
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# expire GIF images after a month in the client's cache<br />
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ExpiresByType image/gif A2592000<br />
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# HTML documents are good for a week from the<br />
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# time they were changed<br />
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ExpiresByType text/html M604800
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</code></p></div>
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<p>Note that this directive only has effect if
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<code>ExpiresActive On</code> has been specified. It overrides,
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for the specified MIME type <em>only</em>, any expiration date
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set by the <code class="directive"><a href="#expiresdefault">ExpiresDefault</a></code>
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directive.</p>
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<p>You can also specify the expiration time calculation using
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an <a href="#AltSyn">alternate syntax</a>, described earlier in
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this document.</p>
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</div>
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<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
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<div class="directive-section"><h2><a name="ExpiresDefault" id="ExpiresDefault">ExpiresDefault</a> <a name="expiresdefault" id="expiresdefault">Directive</a></h2>
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<table class="directive">
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<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Default algorithm for calculating expiration time</td></tr>
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<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ExpiresDefault <var><code>seconds</var></code></td></tr>
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<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
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<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>Indexes</td></tr>
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<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr>
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<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_expires</td></tr>
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</table>
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<p>This directive sets the default algorithm for calculating the
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expiration time for all documents in the affected realm. It can be
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overridden on a type-by-type basis by the <code class="directive"><a href="#expiresbytype">ExpiresByType</a></code> directive. See the
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description of that directive for details about the syntax of the
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argument, and the <a href="#AltSyn">alternate syntax</a>
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description as well.</p>
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</div>
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</div>
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<div class="bottomlang">
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<p><span>Available Languages: </span><a href="../en/mod/mod_expires.html" title="English"> en </a> |
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<a href="../fr/mod/mod_expires.html" hreflang="fr" rel="alternate" title="Français"> fr </a> |
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<a href="../ja/mod/mod_expires.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> |
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<a href="../ko/mod/mod_expires.html" hreflang="ko" rel="alternate" title="Korean"> ko </a></p>
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</div><div id="footer">
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<p class="apache">Copyright 2010 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>
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<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>
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