1<?xml version="1.0" encoding="ISO-8859-1"?> 2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 3<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!-- 4 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 5 This file is generated from xml source: DO NOT EDIT 6 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 7 --> 8<title>mod_expires - Apache HTTP Server</title> 9<link href="/style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" /> 10<link href="/style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" /> 11<link href="/style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" /><link rel="stylesheet" type="text/css" href="/style/css/prettify.css" /> 12<script src="/style/scripts/prettify.min.js" type="text/javascript"> 13</script> 14 15<link href="/images/favicon.ico" rel="shortcut icon" /></head> 16<body> 17<div id="page-header"> 18<p class="menu"><a href="/mod/">Modules</a> | <a href="/mod/directives.html">Directives</a> | <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="/glossary.html">Glossary</a> | <a href="/sitemap.html">Sitemap</a></p> 19<p class="apache">Apache HTTP Server Version 2.4</p> 20<img alt="" src="/images/feather.gif" /></div> 21<div class="up"><a href="./"><img title="<-" alt="<-" src="/images/left.gif" /></a></div> 22<div id="path"> 23<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 2.4</a> > <a href="./">Modules</a></div> 24<div id="page-content"> 25<div id="preamble"><h1>Apache Module mod_expires</h1> 26<div class="toplang"> 27<p><span>Available Languages: </span><a href="/en/mod/mod_expires.html" title="English"> en </a> | 28<a href="/fr/mod/mod_expires.html" hreflang="fr" rel="alternate" title="Fran�ais"> fr </a> | 29<a href="/ja/mod/mod_expires.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> | 30<a href="/ko/mod/mod_expires.html" hreflang="ko" rel="alternate" title="Korean"> ko </a></p> 31</div> 32<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Generation of <code>Expires</code> and 33<code>Cache-Control</code> HTTP headers according to user-specified 34criteria</td></tr> 35<tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr> 36<tr><th><a href="module-dict.html#ModuleIdentifier">Module�Identifier:</a></th><td>expires_module</td></tr> 37<tr><th><a href="module-dict.html#SourceFile">Source�File:</a></th><td>mod_expires.c</td></tr></table> 38<h3>Summary</h3> 39 40 <p>This module controls the setting of the <code>Expires</code> 41 HTTP header and the <code>max-age</code> directive of the 42 <code>Cache-Control</code> HTTP header in server responses. The 43 expiration date can set to be relative to either the time the 44 source file was last modified, or to the time of the client 45 access.</p> 46 47 <p>These HTTP headers are an instruction to the client about the 48 document's validity and persistence. If cached, the document may 49 be fetched from the cache rather than from the source until this 50 time has passed. After that, the cache copy is considered 51 "expired" and invalid, and a new copy must be obtained from the 52 source.</p> 53 54 <p>To modify <code>Cache-Control</code> directives other than 55 <code>max-age</code> (see <a href="http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.9">RFC 56 2616 section 14.9</a>), you can use the <code class="directive"><a href="/mod/mod_headers.html#header">Header</a></code> directive.</p> 57 58 <p> When the <code>Expires</code> header is already part of the response 59 generated by the server, for example when generated by a CGI script or 60 proxied from an origin server, this module does not change or add 61 an <code>Expires</code> or <code>Cache-Control</code> header.</p> 62</div> 63<div id="quickview"><h3 class="directives">Directives</h3> 64<ul id="toc"> 65<li><img alt="" src="/images/down.gif" /> <a href="#expiresactive">ExpiresActive</a></li> 66<li><img alt="" src="/images/down.gif" /> <a href="#expiresbytype">ExpiresByType</a></li> 67<li><img alt="" src="/images/down.gif" /> <a href="#expiresdefault">ExpiresDefault</a></li> 68</ul> 69<h3>Topics</h3> 70<ul id="topics"> 71<li><img alt="" src="/images/down.gif" /> <a href="#AltSyn">Alternate Interval Syntax</a></li> 72</ul><ul class="seealso"><li><a href="#comments_section">Comments</a></li></ul></div> 73<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 74<div class="section"> 75<h2><a name="AltSyn" id="AltSyn">Alternate Interval Syntax</a></h2> 76 <p>The <code class="directive"><a href="#expiresdefault">ExpiresDefault</a></code> and 77 <code class="directive"><a href="#expiresbytype">ExpiresByType</a></code> directives 78 can also be defined in a more readable syntax of the form:</p> 79 80 <pre class="prettyprint lang-config">ExpiresDefault "<var>base</var> [plus <var>num</var> <var>type</var>] [<var>num</var> <var>type</var>] ..." 81ExpiresByType type/encoding "<var>base</var> [plus <var>num</var> <var>type</var>] [<var>num</var> <var>type</var>] ..."</pre> 82 83 84 <p>where <var>base</var> is one of:</p> 85 86 <ul> 87 <li><code>access</code></li> 88 89 <li><code>now</code> (equivalent to 90 '<code>access</code>')</li> 91 92 <li><code>modification</code></li> 93 </ul> 94 95 <p>The <code>plus</code> keyword is optional. <var>num</var> 96 should be an integer value [acceptable to <code>atoi()</code>], 97 and <var>type</var> is one of:</p> 98 99 <ul> 100 <li><code>years</code></li> 101 <li><code>months</code></li> 102 <li><code>weeks</code></li> 103 <li><code>days</code></li> 104 <li><code>hours</code></li> 105 <li><code>minutes</code></li> 106 <li><code>seconds</code></li> 107 </ul> 108 109 <p>For example, any of the following directives can be used to 110 make documents expire 1 month after being accessed, by 111 default:</p> 112 113 <pre class="prettyprint lang-config">ExpiresDefault "access plus 1 month" 114ExpiresDefault "access plus 4 weeks" 115ExpiresDefault "access plus 30 days"</pre> 116 117 118 <p>The expiry time can be fine-tuned by adding several 119 '<var>num</var> <var>type</var>' clauses:</p> 120 121 <pre class="prettyprint lang-config">ExpiresByType text/html "access plus 1 month 15 days 2 hours" 122ExpiresByType image/gif "modification plus 5 hours 3 minutes"</pre> 123 124 125 <p>Note that if you use a modification date based setting, the 126 Expires header will <strong>not</strong> be added to content 127 that does not come from a file on disk. This is due to the fact 128 that there is no modification time for such content.</p> 129</div> 130<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 131<div class="directive-section"><h2><a name="ExpiresActive" id="ExpiresActive">ExpiresActive</a> <a name="expiresactive" id="expiresactive">Directive</a></h2> 132<table class="directive"> 133<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enables generation of <code>Expires</code> 134headers</td></tr> 135<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ExpiresActive On|Off</code></td></tr> 136<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ExpiresActive Off</code></td></tr> 137<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr> 138<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>Indexes</td></tr> 139<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr> 140<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_expires</td></tr> 141</table> 142 <p>This directive enables or disables the generation of the 143 <code>Expires</code> and <code>Cache-Control</code> headers for 144 the document realm in question. (That is, if found in an 145 <code>.htaccess</code> file, for instance, it applies only to 146 documents generated from that directory.) If set to 147 <code>Off</code>, the headers will not be generated for any 148 document in the realm (unless overridden at a lower level, such as 149 an <code>.htaccess</code> file overriding a server config 150 file). If set to <code>On</code>, the headers will be added to 151 served documents according to the criteria defined by the 152 <code class="directive"><a href="#expiresbytype">ExpiresByType</a></code> and 153 <code class="directive"><a href="#expiresdefault">ExpiresDefault</a></code> 154 directives (<em>q.v.</em>).</p> 155 156 <p>Note that this directive does not guarantee that an 157 <code>Expires</code> or <code>Cache-Control</code> header will be 158 generated. If the criteria aren't met, no header will be sent, and 159 the effect will be as though this directive wasn't even 160 specified.</p> 161 162</div> 163<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 164<div class="directive-section"><h2><a name="ExpiresByType" id="ExpiresByType">ExpiresByType</a> <a name="expiresbytype" id="expiresbytype">Directive</a></h2> 165<table class="directive"> 166<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Value of the <code>Expires</code> header configured 167by MIME type</td></tr> 168<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ExpiresByType <var>MIME-type</var> 169<var><code>seconds</var></code></td></tr> 170<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr> 171<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>Indexes</td></tr> 172<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr> 173<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_expires</td></tr> 174</table> 175 <p>This directive defines the value of the <code>Expires</code> 176 header and the <code>max-age</code> directive of the 177 <code>Cache-Control</code> header generated for documents of the 178 specified type (<em>e.g.</em>, <code>text/html</code>). The second 179 argument sets the number of seconds that will be added to a base 180 time to construct the expiration date. The <code>Cache-Control: 181 max-age</code> is calculated by subtracting the request time from 182 the expiration date and expressing the result in seconds.</p> 183 184 <p>The base time is either the last modification time of the 185 file, or the time of the client's access to the document. Which 186 should be used is specified by the 187 <code><var><code></var></code> field; <code>M</code> 188 means that the file's last modification time should be used as 189 the base time, and <code>A</code> means the client's access 190 time should be used.</p> 191 192 <p>The difference in effect is subtle. If <code>M</code> is used, 193 all current copies of the document in all caches will expire at 194 the same time, which can be good for something like a weekly 195 notice that's always found at the same URL. If <code>A</code> is 196 used, the date of expiration is different for each client; this 197 can be good for image files that don't change very often, 198 particularly for a set of related documents that all refer to 199 the same images (<em>i.e.</em>, the images will be accessed 200 repeatedly within a relatively short timespan).</p> 201 202 <div class="example"><h3>Example:</h3><pre class="prettyprint lang-config"># enable expirations 203ExpiresActive On 204# expire GIF images after a month in the client's cache 205ExpiresByType image/gif A2592000 206# HTML documents are good for a week from the 207# time they were changed 208ExpiresByType text/html M604800</pre> 209</div> 210 211 <p>Note that this directive only has effect if 212 <code>ExpiresActive On</code> has been specified. It overrides, 213 for the specified MIME type <em>only</em>, any expiration date 214 set by the <code class="directive"><a href="#expiresdefault">ExpiresDefault</a></code> 215 directive.</p> 216 217 <p>You can also specify the expiration time calculation using 218 an <a href="#AltSyn">alternate syntax</a>, described earlier in 219 this document.</p> 220 221</div> 222<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 223<div class="directive-section"><h2><a name="ExpiresDefault" id="ExpiresDefault">ExpiresDefault</a> <a name="expiresdefault" id="expiresdefault">Directive</a></h2> 224<table class="directive"> 225<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Default algorithm for calculating expiration time</td></tr> 226<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ExpiresDefault <var><code>seconds</var></code></td></tr> 227<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr> 228<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>Indexes</td></tr> 229<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr> 230<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_expires</td></tr> 231</table> 232 <p>This directive sets the default algorithm for calculating the 233 expiration time for all documents in the affected realm. It can be 234 overridden on a type-by-type basis by the <code class="directive"><a href="#expiresbytype">ExpiresByType</a></code> directive. See the 235 description of that directive for details about the syntax of the 236 argument, and the <a href="#AltSyn">alternate syntax</a> 237 description as well.</p> 238 239</div> 240</div> 241<div class="bottomlang"> 242<p><span>Available Languages: </span><a href="/en/mod/mod_expires.html" title="English"> en </a> | 243<a href="/fr/mod/mod_expires.html" hreflang="fr" rel="alternate" title="Fran�ais"> fr </a> | 244<a href="/ja/mod/mod_expires.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> | 245<a href="/ko/mod/mod_expires.html" hreflang="ko" rel="alternate" title="Korean"> ko </a></p> 246</div><div class="top"><a href="#page-header"><img src="/images/up.gif" alt="top" /></a></div><div class="section"><h2><a id="comments_section" name="comments_section">Comments</a></h2><div class="warning"><strong>Notice:</strong><br />This is not a Q&A section. 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