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<parentdocument href="./">Rewrite</parentdocument>

<title>Redirecting and Remapping with mod_rewrite</title>

<summary>

<p>This document supplements the <module>mod_rewrite</module>

<a href="/mod_rewrite.html">reference documentation</a>. It describes

how you can use <module>mod_rewrite</module> to redirect and remap

request. This includes many examples of common uses of mod_rewrite,

including detailed descriptions of how each works.</p>

<note type="warning">Note that many of these examples won't work unchanged in your

particular server configuration, so it's important that you understand

them, rather than merely cutting and pasting the examples into your

configuration.</note>

</summary>

<seealso><a href="/mod/mod_rewrite.html">Module documentation</a></seealso>

<seealso><a href="intro.html">mod_rewrite introduction</a></seealso>

<section id="old-to-new">

<title>From Old to New (internal)</title>

<dl>

<dt>Description:</dt>

<dd>

<p>Assume we have recently renamed the page

<code>foo.html</code> to <code>bar.html</code> and now want

to provide the old URL for backward compatibility. However,

we want that users of the old URL even not recognize that

the pages was renamed - that is, we don't want the address to

change in their browser.</p>

</dd>

<dt>Solution:</dt>

<dd>

<p>We rewrite the old URL to the new one internally via the

following rule:</p>

<example><pre>

RewriteEngine on

RewriteRule ^<strong>/old</strong>\.html$ <strong>/new</strong>.html [PT]

</pre></example>

</dd>

</dl>

</section>

<section id="old-to-new-extern">

<title>Rewriting From Old to New (external)</title>

<dl>

<dt>Description:</dt>

<dd>

<p>Assume again that we have recently renamed the page

<code>foo.html</code> to <code>bar.html</code> and now want

to provide the old URL for backward compatibility. But this

time we want that the users of the old URL get hinted to

the new one, i.e. their browsers Location field should

change, too.</p>

</dd>

<dt>Solution:</dt>

<dd>

<p>We force a HTTP redirect to the new URL which leads to a

change of the browsers and thus the users view:</p>

<example><pre>

RewriteEngine on

RewriteRule ^<strong>/foo</strong>\.html$ <strong>bar</strong>.html [<strong>R</strong>]

</pre></example>

</dd>

<dt>Discussion</dt>

<dd>

<p>In this example, as contrasted to the <a

href="#old-to-new-intern">internal</a> example above, we can simply

use the Redirect directive. mod_rewrite was used in that earlier

example in order to hide the redirect from the client:</p>

<example>

Redirect /foo.html /bar.html

</example>

</dd>

</dl>

</section>

<section id="static-to-dynamic">

<title>From Static to Dynamic</title>

<dl>

<dt>Description:</dt>

<dd>

<p>How can we transform a static page

<code>foo.html</code> into a dynamic variant

<code>foo.cgi</code> in a seamless way, i.e. without notice

by the browser/user.</p>

</dd>

<dt>Solution:</dt>

<dd>

<p>We just rewrite the URL to the CGI-script and force the

handler to be <strong>cgi-script</strong> so that it is

executed as a CGI program.

This way a request to <code>/~quux/foo.html</code>

internally leads to the invocation of

<code>/~quux/foo.cgi</code>.</p>

<example><pre>

RewriteEngine on

RewriteBase /~quux/

RewriteRule ^foo\.<strong>html</strong>$ foo.<strong>cgi</strong> [H=<strong>cgi-script</strong>]

</pre></example>

</dd>

</dl>

</section>

<section id="backward-compatibility">

<title>Backward Compatibility for file extension change</title>

<dl>

<dt>Description:</dt>

<dd>

<p>How can we make URLs backward compatible (still

existing virtually) after migrating <code>document.YYYY</code>

to <code>document.XXXX</code>, e.g. after translating a

bunch of <code>.html</code> files to <code>.php</code>?</p>

</dd>

<dt>Solution:</dt>

<dd>

<p>We rewrite the name to its basename and test for

existence of the new extension. If it exists, we take

that name, else we rewrite the URL to its original state.</p>

<example><pre>

# backward compatibility ruleset for

# rewriting document.html to document.php

# when and only when document.php exists

RewriteEngine on

RewriteCond $1.php -f

RewriteCond $1.html !-f

RewriteRule ^(.*).html$ $1.php

</pre></example>

</dd>

<dt>Discussion</dt>

<dd>

<p>This example uses an often-overlooked feature of mod_rewrite,

by taking advantage of the order of execution of the ruleset. In

particular, mod_rewrite evaluates the left-hand-side of the

RewriteRule before it evaluates the RewriteCond directives.

Consequently, $1 is already defined by the time the RewriteRule

directives are evaluated. This allows us to test for the existence

of the the original (<code>document.html</code>) and target

(<code>document.php</code>) files using the same base filename.</p>

<p>This ruleset is designed to use in a per-directory context (In a

&lt;Directory&gt; block or in a .htaccess file), so that the

<code>-f</code> checks are looking at the correct directory path.

You may need to set a <directive

module="mod_rewite">RewriteBase</directive> directive to specify the

directory base that you're working in.</p>

</dd>

</dl>

</section>

<section id="canonicalhost"><title>Canonical Hostnames</title>

<dl>

<dt>Description:</dt>

<dd>The goal of this rule is to force the use of a particular

hostname, in preference to other hostnames which may be used to

reach the same site. For example, if you wish to force the use

of <strong>www.example.com</strong> instead of

<strong>example.com</strong>, you might use a variant of the

following recipe.</dd>

<dt>Solution:</dt>

<dd>

<p>For sites running on a port other than 80:</p>

<example><pre>

RewriteCond %{HTTP_HOST} !^www\.example\.com [NC]

RewriteCond %{HTTP_HOST} !^$

RewriteCond %{SERVER_PORT} !^80$

RewriteRule ^/?(.*) http://www.example.com:%{SERVER_PORT}/$1 [L,R,NE]

</pre></example>

<p>And for a site running on port 80</p>

<example><pre>

RewriteCond %{HTTP_HOST} !^www\.example\.com [NC]

RewriteCond %{HTTP_HOST} !^$

RewriteRule ^/?(.*) http://www.example.com/$1 [L,R,NE]

</pre></example>

<p>

If you wanted to do this generically for all domain names - that

is, if you want to redirect <strong>example.com</strong> to

<strong>www.example.com</strong> for all possible values of

<strong>example.com</strong>, you could use the following

recipe:</p>

<example><pre>

RewriteCond %{HTTP_HOST} !^www\. [NC]

RewriteCond %{HTTP_HOST} !^$

RewriteRule ^/?(.*) http://www.%{HTTP_HOST}/$1 [L,R,NE]

</pre></example>

<p>These rulesets will work either in your main server configuration

file, or in a <code>.htaccess</code> file placed in the <directive

module="core">DocumentRoot</directive> of the server.</p>

</dd>

</dl>

</section>

<section id="multipledirs">

<title>Search for pages in more than one directory</title>

<dl>

<dt>Description:</dt>

<dd>

<p>A particular resource might exist in one of several places, and

we want to look in those places for the resource when it is

requested. Perhaps we've recently rearranged our directory

structure, dividing content into several locations.</p>

</dd>

<dt>Solution:</dt>

<dd>

<p>The following ruleset searches in two directories to find the

resource, and, if not finding it in either place, will attempt to

just serve it out of the location requested.</p>

<example><pre>

RewriteEngine on

# first try to find it in dir1/...

# ...and if found stop and be happy:

RewriteCond %{DOCUMENT_ROOT}/<strong>dir1</strong>/%{REQUEST_URI} -f

RewriteRule ^(.+) %{DOCUMENT_ROOT}/<strong>dir1</strong>/$1 [L]

# second try to find it in dir2/...

# ...and if found stop and be happy:

RewriteCond %{DOCUMENT_ROOT}/<strong>dir2</strong>/%{REQUEST_URI} -f

RewriteRule ^(.+) %{DOCUMENT_ROOT}/<strong>dir2</strong>/$1 [L]

# else go on for other Alias or ScriptAlias directives,

# etc.

RewriteRule ^(.+) - [PT]

</pre></example>

</dd>

</dl>

</section>

<section id="archive-access-multiplexer">

<title>Redirecting to Geographically Distributed Servers</title>

<dl>

<dt>Description:</dt>

<dd>

<p>We have numerous mirrors of our website, and want to redirect

people to the one that is located in the country where they are

located.</p>

</dd>

<dt>Solution:</dt>

<dd>

<p>Looking at the hostname of the requesting client, we determine

which country they are coming from. If we can't do a lookup on their

IP address, we fall back to a default server.</p>

<p>We'll use <directive module="mod_rewrite">RewriteMap</directive>

directive to build a list of servers that we wish to use.</p>

<example><pre>

HostnameLookups on

RewriteEngine on

RewriteMap multiplex txt:/path/to/map.mirrors

RewriteCond %{REMOTE_HOST} ([a-z]+)$ [NC]

RewriteRule ^(.*)$ ${multiplex:<strong>%1</strong>|http://www.example.com/}$1 [R,L]

</pre></example>

<example><pre>

## map.mirrors -- Multiplexing Map

de http://www.example.de/

uk http://www.example.uk/

com http://www.example.com/

##EOF##

</pre></example>

</dd>

<dt>Discussion</dt>

<dd>

<note type="warning">This ruleset relies on

<directive module="core">HostNameLookups</directive>

being set <code>on</code>, which can be

a significant performance hit.</note>

<p>The <directive module="mod_rewrite">RewriteCond</directive>

directive captures the last portion of the hostname of the

requesting client - the country code - and the following RewriteRule

uses that value to look up the appropriate mirror host in the map

file.</p>

</dd>

</dl>

</section>

</manualpage>