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<?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> <meta content="text/html; charset=ISO-8859-1" http-equiv="Content-Type" /> <!-- XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX This file is generated from xml source: DO NOT EDIT XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX --> <title>mod_headers - Apache HTTP Server Version 2.2</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 rel="stylesheet" type="text/css" href="../style/css/prettify.css" /> <script src="../style/scripts/prettify.min.js" type="text/javascript"> </script> <link href="../images/favicon.ico" rel="shortcut icon" /><link href="http://httpd.apache.org/docs/current/mod/mod_headers.html" rel="canonical" /></head> <body> <div id="page-header"> <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> <p class="apache">Apache HTTP Server Version 2.2</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 2.2</a> > <a href="./">Modules</a></div> <div id="page-content"> <div class="retired"><h4>Please note</h4> <p> This document refers to a legacy release (<strong>2.2</strong>) of Apache httpd. The active release (<strong>2.4</strong>) is documented <a href="http://httpd.apache.org/docs/current">here</a>. If you have not already upgraded, please follow <a href="http://httpd.apache.org/docs/current/upgrading.html">this link</a> for more information.</p> <p>You may follow <a href="http://httpd.apache.org/docs/current/mod/mod_headers.html">this link</a> to go to the current version of this document.</p></div><div id="preamble"><h1>Apache Module mod_headers</h1> <div class="toplang"> <p><span>Available Languages: </span><a href="../en/mod/mod_headers.html" title="English"> en </a> | <a href="../ja/mod/mod_headers.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> | <a href="../ko/mod/mod_headers.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>Customization of HTTP request and response headers</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>headers_module</td></tr> <tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_headers.c</td></tr></table> <h3>Summary</h3> <p>This module provides directives to control and modify HTTP request and response headers. Headers can be merged, replaced or removed.</p> </div> <div id="quickview"><h3>Topics</h3> <ul id="topics"> <li><img alt="" src="../images/down.gif" /> <a href="#order">Order of Processing</a></li> <li><img alt="" src="../images/down.gif" /> <a href="#early">Early and Late Processing</a></li> <li><img alt="" src="../images/down.gif" /> <a href="#examples">Examples</a></li> </ul><h3 class="directives">Directives</h3> <ul id="toc"> <li><img alt="" src="../images/down.gif" /> <a href="#header">Header</a></li> <li><img alt="" src="../images/down.gif" /> <a href="#requestheader">RequestHeader</a></li> </ul> <ul class="seealso"><li><a href="#comments_section">Comments</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="order" id="order">Order of Processing</a></h2> <p>The directives provided by <code class="module"><a href="../mod/mod_headers.html">mod_headers</a></code> can occur almost anywhere within the server configuration, and can be limited in scope by enclosing them in <a href="../sections.html">configuration sections</a>.</p> <p>Order of processing is important and is affected both by the order in the configuration file and by placement in <a href="../sections.html#mergin">configuration sections</a>. These two directives have a different effect if reversed:</p> <div class="example"><p><code> RequestHeader append MirrorID "mirror 12"<br /> RequestHeader unset MirrorID </code></p></div> <p>This way round, the <code>MirrorID</code> header is not set. If reversed, the MirrorID header is set to "mirror 12".</p> </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> <div class="section"> <h2><a name="early" id="early">Early and Late Processing</a></h2> <p><code class="module"><a href="../mod/mod_headers.html">mod_headers</a></code> can be applied either early or late in the request. The normal mode is late, when <em>Request</em> Headers are set immediately before running the content generator and <em>Response</em> Headers just as the response is sent down the wire. Always use Late mode in an operational server.</p> <p>Early mode is designed as a test/debugging aid for developers. Directives defined using the <code>early</code> keyword are set right at the beginning of processing the request. This means they can be used to simulate different requests and set up test cases, but it also means that headers may be changed at any time by other modules before generating a Response.</p> <p>Because early directives are processed before the request path's configuration is traversed, early headers can only be set in a main server or virtual host context. Early directives cannot depend on a request path, so they will fail in contexts such as <code><Directory></code> or <code><Location></code>.</p> </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> <div class="section"> <h2><a name="examples" id="examples">Examples</a></h2> <ol> <li> Copy all request headers that begin with "TS" to the response headers: <div class="example"><p><code> Header echo ^TS </code></p></div> </li> <li> Add a header, <code>MyHeader</code>, to the response including a timestamp for when the request was received and how long it took to begin serving the request. This header can be used by the client to intuit load on the server or in isolating bottlenecks between the client and the server. <div class="example"><p><code> Header set MyHeader "%D %t" </code></p></div> <p>results in this header being added to the response:</p> <div class="example"><p><code> MyHeader: D=3775428 t=991424704447256 </code></p></div> </li> <li> Say hello to Joe <div class="example"><p><code> Header set MyHeader "Hello Joe. It took %D microseconds \<br /> for Apache to serve this request." </code></p></div> <p>results in this header being added to the response:</p> <div class="example"><p><code> MyHeader: Hello Joe. It took D=3775428 microseconds for Apache to serve this request. </code></p></div> </li> <li> Conditionally send <code>MyHeader</code> on the response if and only if header <code>MyRequestHeader</code> is present on the request. This is useful for constructing headers in response to some client stimulus. Note that this example requires the services of the <code class="module"><a href="../mod/mod_setenvif.html">mod_setenvif</a></code> module. <div class="example"><p><code> SetEnvIf MyRequestHeader myvalue HAVE_MyRequestHeader<br /> Header set MyHeader "%D %t mytext" env=HAVE_MyRequestHeader </code></p></div> <p>If the header <code>MyRequestHeader: myvalue</code> is present on the HTTP request, the response will contain the following header:</p> <div class="example"><p><code> MyHeader: D=3775428 t=991424704447256 mytext </code></p></div> </li> <li> Enable DAV to work with Apache running HTTP through SSL hardware (<a href="http://svn.haxx.se/users/archive-2006-03/0549.shtml">problem description</a>) by replacing <var>https:</var> with <var>http:</var> in the <var>Destination</var> header: <div class="example"><p><code> RequestHeader edit Destination ^https: http: early </code></p></div> </li> <li> Set the same header value under multiple nonexclusive conditions, but do not duplicate the value in the final header. If all of the following conditions applied to a request (i.e., if the <code>CGI</code>, <code>NO_CACHE</code> and <code>NO_STORE</code> environment variables all existed for the request): <div class="example"><p><code> Header merge Cache-Control no-cache env=CGI<br /> Header merge Cache-Control no-cache env=NO_CACHE<br /> Header merge Cache-Control no-store env=NO_STORE </code></p></div> <p>then the response would contain the following header:</p> <div class="example"><p><code> Cache-Control: no-cache, no-store </code></p></div> <p>If <code>append</code> was used instead of <code>merge</code>, then the response would contain the following header:</p> <div class="example"><p><code> Cache-Control: no-cache, no-cache, no-store </code></p></div> </li> </ol> </div> <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> <div class="directive-section"><h2><a name="Header" id="Header">Header</a> <a name="header" id="header">Directive</a></h2> <table class="directive"> <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Configure HTTP response headers</td></tr> <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>Header [<var>condition</var>] set|append|merge|add|unset|echo|edit <var>header</var> [<var>value</var>] [<var>replacement</var>] [early|env=[!]<var>variable</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>FileInfo</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_headers</td></tr> <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>The <code>merge</code> argument is available in version 2.2.9 and later. The <code>edit</code> argument is available in version 2.2.4 and later.</td></tr> </table> <p>This directive can replace, merge or remove HTTP response headers. The header is modified just after the content handler and output filters are run, allowing outgoing headers to be modified.</p> <p> The optional <var>condition</var> argument determines which internal table of responses headers this directive will operate against. Other components of the server may have stored their response headers in either the table that corresponds to <code>onsuccess</code> or the table that corresponds to <code>always</code>. "Always" in this context refers to whether headers you add will be sent during both a successful and unsucessful response, but if your action is a function of an existing header, you will have to read on for further complications.</p> <p> The default value of <code>onsuccess</code> may need to be changed to <code>always</code> under the circumstances similar to those listed below. Note also that repeating this directive with both conditions makes sense in some scenarios because <code>always</code> is not a superset of <code>onsuccess</code> with respect to existing headers:</p> <ul> <li> You're adding a header to a non-success (non-2xx) response, such as a redirect, in which case only the table corresponding to <code>always</code> is used in the ultimate response.</li> <li> You're modifying or removing a header generated by a CGI script, in which case the CGI scripts are in the table corresponding to <code>always</code> and not in the default table.</li> <li> You're modifying or removing a header generated by some piece of the server but that header is not being found by the default <code>onsuccess</code> condition.</li> </ul> <p>The action it performs is determined by the first argument (second argument if a <var>condition</var> is specified). This can be one of the following values:</p> <dl> <dt><code>set</code></dt> <dd>The response header is set, replacing any previous header with this name. The <var>value</var> may be a format string.</dd> <dt><code>append</code></dt> <dd>The response header is appended to any existing header of the same name. When a new value is merged onto an existing header it is separated from the existing header with a comma. This is the HTTP standard way of giving a header multiple values.</dd> <dt><code>merge</code></dt> <dd>The response header is appended to any existing header of the same name, unless the value to be appended already appears in the header's comma-delimited list of values. When a new value is merged onto an existing header it is separated from the existing header with a comma. This is the HTTP standard way of giving a header multiple values. Values are compared in a case sensitive manner, and after all format specifiers have been processed. Values in double quotes are considered different from otherwise identical unquoted values. <em>Available in version 2.2.9 and later.</em></dd> <dt><code>add</code></dt> <dd>The response header is added to the existing set of headers, even if this header already exists. This can result in two (or more) headers having the same name. This can lead to unforeseen consequences, and in general <code>set</code>, <code>append</code> or <code>merge</code> should be used instead.</dd> <dt><code>unset</code></dt> <dd>The response header of this name is removed, if it exists. If there are multiple headers of the same name, all will be removed. <var>value</var> must be omitted.</dd> <dt><code>echo</code></dt> <dd>Request headers with this name are echoed back in the response headers. <var>header</var> may be a <a class="glossarylink" href="../glossary.html#regex" title="see glossary">regular expression</a>. <var>value</var> must be omitted.</dd> <dt><code>edit</code></dt> <dd>If this response header exists, its value is transformed according to a <a class="glossarylink" href="../glossary.html#regex" title="see glossary">regular expression</a> search-and-replace. The <var>value</var> argument is a <a class="glossarylink" href="../glossary.html#regex" title="see glossary">regular expression</a>, and the <var>replacement</var> is a replacement string, which may contain backreferences. <em>Available in version 2.2.4 and later.</em></dd> </dl> <p>This argument is followed by a <var>header</var> name, which can include the final colon, but it is not required. Case is ignored for <code>set</code>, <code>append</code>, <code>merge</code>, <code>add</code>, <code>unset</code> and <code>edit</code>. The <var>header</var> name for <code>echo</code> is case sensitive and may be a <a class="glossarylink" href="../glossary.html#regex" title="see glossary">regular expression</a>.</p> <p>For <code>set</code>, <code>append</code>, <code>merge</code> and <code>add</code> a <var>value</var> is specified as the next argument. If <var>value</var> contains spaces, it should be surrounded by double quotes. <var>value</var> may be a character string, a string containing format specifiers or a combination of both. The following format specifiers are supported in <var>value</var>:</p> <table class="bordered"><tr class="header"><th>Format</th><th>Description</th></tr> <tr><td><code>%%</code></td> <td>The percent sign</td></tr> <tr class="odd"><td><code>%t</code></td> <td>The time the request was received in Universal Coordinated Time since the epoch (Jan. 1, 1970) measured in microseconds. The value is preceded by <code>t=</code>.</td></tr> <tr><td><code>%D</code></td> <td>The time from when the request was received to the time the headers are sent on the wire. This is a measure of the duration of the request. The value is preceded by <code>D=</code>. The value is measured in microseconds.</td></tr> <tr class="odd"><td><code>%{FOOBAR}e</code></td> <td>The contents of the <a href="../env.html">environment variable</a> <code>FOOBAR</code>.</td></tr> <tr><td><code>%{FOOBAR}s</code></td> <td>The contents of the <a href="mod_ssl.html#envvars">SSL environment variable</a> <code>FOOBAR</code>, if <code class="module"><a href="../mod/mod_ssl.html">mod_ssl</a></code> is enabled.</td></tr> </table> <div class="note"><h3>Note</h3> <p>The <code>%s</code> format specifier is only available in Apache 2.1 and later; it can be used instead of <code>%e</code> to avoid the overhead of enabling <code>SSLOptions +StdEnvVars</code>. If <code>SSLOptions +StdEnvVars</code> must be enabled anyway for some other reason, <code>%e</code> will be more efficient than <code>%s</code>.</p> </div> <p>For <code>edit</code> there is both a <var>value</var> argument which is a <a class="glossarylink" href="../glossary.html#regex" title="see glossary">regular expression</a>, and an additional <var>replacement</var> string.</p> <p>The <code class="directive">Header</code> directive may be followed by an an additional argument, which may be used to specify conditions under which the action will be taken, or may be the keyword <code>early</code> to specify <a href="#early">early processing</a>. If the <a href="../env.html">environment variable</a> specified in the <code>env=<var>...</var></code> argument exists (or if the environment variable does not exist and <code>env=!<var>...</var></code> is specified) then the action specified by the <code class="directive">Header</code> directive will take effect. Otherwise, the directive will have no effect on the request.</p> <p>Except in <a href="#early">early</a> mode, the <code class="directive">Header</code> directives are processed just before the response is sent to the network. This means that it is possible to set and/or override most headers, except for some headers added by the HTTP header filter. Prior to 2.2.12, it was not possible to change the Content-Type header with this directive.</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="RequestHeader" id="RequestHeader">RequestHeader</a> <a name="requestheader" id="requestheader">Directive</a></h2> <table class="directive"> <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Configure HTTP request headers</td></tr> <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>RequestHeader set|append|merge|add|unset|edit <var>header</var> [<var>value</var>] [<var>replacement</var>] [early|env=[!]<var>variable</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>FileInfo</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_headers</td></tr> <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>The <code>merge</code> argument is available in version 2.2.9 and later. The <code>edit</code> argument is available in version 2.2.4 and later.</td></tr> </table> <p>This directive can replace, merge, change or remove HTTP request headers. The header is modified just before the content handler is run, allowing incoming headers to be modified. The action it performs is determined by the first argument. This can be one of the following values:</p> <dl> <dt><code>set</code></dt> <dd>The request header is set, replacing any previous header with this name</dd> <dt><code>append</code></dt> <dd>The request header is appended to any existing header of the same name. When a new value is merged onto an existing header it is separated from the existing header with a comma. This is the HTTP standard way of giving a header multiple values.</dd> <dt><code>merge</code></dt> <dd>The request header is appended to any existing header of the same name, unless the value to be appended already appears in the existing header's comma-delimited list of values. When a new value is merged onto an existing header it is separated from the existing header with a comma. This is the HTTP standard way of giving a header multiple values. Values are compared in a case sensitive manner, and after all format specifiers have been processed. Values in double quotes are considered different from otherwise identical unquoted values. <em>Available in version 2.2.9 and later.</em></dd> <dt><code>add</code></dt> <dd>The request header is added to the existing set of headers, even if this header already exists. This can result in two (or more) headers having the same name. This can lead to unforeseen consequences, and in general <code>set</code>, <code>append</code> or <code>merge</code> should be used instead.</dd> <dt><code>unset</code></dt> <dd>The request header of this name is removed, if it exists. If there are multiple headers of the same name, all will be removed. <var>value</var> must be omitted.</dd> <dt><code>edit</code></dt> <dd>If this request header exists, its value is transformed according to a <a class="glossarylink" href="../glossary.html#regex" title="see glossary">regular expression</a> search-and-replace. The <var>value</var> argument is a <a class="glossarylink" href="../glossary.html#regex" title="see glossary">regular expression</a>, and the <var>replacement</var> is a replacement string, which may contain backreferences. <em>Available in version 2.2.4 and later</em>.</dd> </dl> <p>This argument is followed by a header name, which can include the final colon, but it is not required. Case is ignored. For <code>set</code>, <code>append</code>, <code>merge</code> and <code>add</code> a <var>value</var> is given as the third argument. If a <var>value</var> contains spaces, it should be surrounded by double quotes. For <code>unset</code>, no <var>value</var> should be given. <var>value</var> may be a character string, a string containing format specifiers or a combination of both. The supported format specifiers are the same as for the <code class="directive"><a href="#header">Header</a></code>, please have a look there for details. For <code>edit</code> both a <var>value</var> and a <var>replacement</var> are required, and are a <a class="glossarylink" href="../glossary.html#regex" title="see glossary">regular expression</a> and a replacement string respectively.</p> <p>The <code class="directive">RequestHeader</code> directive may be followed by an additional argument, which may be used to specify conditions under which the action will be taken, or may be the keyword <code>early</code> to specify <a href="#early">early processing</a>. If the <a href="../env.html">environment variable</a> specified in the <code>env=<var>...</var></code> argument exists (or if the environment variable does not exist and <code>env=!<var>...</var></code> is specified) then the action specified by the <code class="directive">RequestHeader</code> directive will take effect. Otherwise, the directive will have no effect on the request.</p> <p>Except in <a href="#early">early</a> mode, the <code class="directive">RequestHeader</code> directive is processed just before the request is run by its handler in the fixup phase. This should allow headers generated by the browser, or by Apache input filters to be overridden or modified.</p> </div> </div> <div class="bottomlang"> <p><span>Available Languages: </span><a href="../en/mod/mod_headers.html" title="English"> en </a> | <a href="../ja/mod/mod_headers.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> | <a href="../ko/mod/mod_headers.html" hreflang="ko" rel="alternate" title="Korean"> ko </a></p> </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. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed again by our moderators if they are either implemented or considered invalid/off-topic. 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