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<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/quickreference.html">Directives</a> | <a href="https://cwiki.apache.org/confluence/display/httpd/FAQ">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a> | <a href="https://bz.apache.org/bugzilla/enter_bug.cgi?product=Apache%20httpd-2">Report a bug</a></p>
<p class="apache">Apache HTTP Server Version 2.4</p>
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<a href="https://www.apache.org/">Apache</a> > <a href="https://httpd.apache.org/">HTTP Server</a> > <a href="https://httpd.apache.org/docs/">Documentation</a> > <a href="../">Version 2.4</a> > <a href="./">Rewrite</a></div><div id="page-content"><div id="preamble"><h1>Redirecting and Remapping with mod_rewrite</h1>
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<p><span>Available Languages: </span><a href="../en/rewrite/remapping.html" title="English"> en </a> |
<a href="../fr/rewrite/remapping.html" hreflang="fr" rel="alternate" title="Français"> fr </a></p>
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<p>This document supplements the <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>
<a href="../mod/mod_rewrite.html">reference documentation</a>. It describes
how you can use <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> to redirect and remap
request. This includes many examples of common uses of <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>,
including detailed descriptions of how each works.</p>
</div>
<div id="quickview"><ul id="toc"><li><img alt="" src="../images/down.gif"> <a href="#old-to-new">From Old to New (internal)</a></li>
<li><img alt="" src="../images/down.gif"> <a href="#https-redirect">Forcing HTTPS</a></li>
<li><img alt="" src="../images/down.gif"> <a href="#acme-exemption">Exempting ACME challenge requests from HTTPS redirect</a></li>
<li><img alt="" src="../images/down.gif"> <a href="#trailing-slash">Trailing Slash Normalization</a></li>
<li><img alt="" src="../images/down.gif"> <a href="#front-controller">Front Controller / Application Routing</a></li>
<li><img alt="" src="../images/down.gif"> <a href="#old-to-new-extern">Rewriting From Old to New (external)</a></li>
<li><img alt="" src="../images/down.gif"> <a href="#movehomedirs">Resource Moved to Another Server</a></li>
<li><img alt="" src="../images/down.gif"> <a href="#backward-compatibility">Backward Compatibility for file extension change</a></li>
<li><img alt="" src="../images/down.gif"> <a href="#canonicalhost">Canonical Hostnames</a></li>
<li><img alt="" src="../images/down.gif"> <a href="#multipledirs">Search for pages in more than one directory</a></li>
<li><img alt="" src="../images/down.gif"> <a href="#canonicalurl">Canonical URLs</a></li>
<li><img alt="" src="../images/down.gif"> <a href="#moveddocroot">Moved <code>DocumentRoot</code></a></li>
<li><img alt="" src="../images/down.gif"> <a href="#rewrite-query">Rewrite query string</a></li>
<li><img alt="" src="../images/down.gif"> <a href="#structuredhomedirs">Structured Userdirs</a></li>
<li><img alt="" src="../images/down.gif"> <a href="#redirectanchors">Redirecting Anchors</a></li>
<li><img alt="" src="../images/down.gif"> <a href="#time-dependent">Time-Dependent Rewriting</a></li>
<li><img alt="" src="../images/down.gif"> <a href="#on-the-fly-content">On-the-fly Content-Regeneration</a></li>
</ul><h3>See also</h3><ul class="seealso"><li><a href="../mod/mod_rewrite.html">Module documentation</a></li><li><a href="intro.html">mod_rewrite introduction</a></li><li><a href="htaccess.html">Per-directory Rewrites</a></li><li><a href="flags.html">RewriteRule Flags</a></li><li><a href="vhosts.html">Virtual hosts</a></li><li><a href="rewritemap.html">Using RewriteMap</a></li><li><a href="avoid.html">When not to use mod_rewrite</a></li><li><a href="tech.html">Technical details</a></li></ul></div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif"></a></div>
<div class="section">
<h2 id="old-to-new">From Old to New (internal) <a title="Permanent link" href="#old-to-new" class="permalink">¶</a></h2>
<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>
<pre class="prettyprint lang-config">RewriteEngine on
RewriteRule "^<strong>/foo</strong>\.html$" "<strong>/bar</strong>.html" [PT]</pre>
</dd>
</dl>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif"></a></div>
<div class="section">
<h2 id="https-redirect">Forcing HTTPS <a title="Permanent link" href="#https-redirect" class="permalink">¶</a></h2>
<dl>
<dt>Description:</dt>
<dd>
<p>You want all HTTP requests to be redirected to HTTPS. This
is one of the most common uses of <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>,
but in most cases it is better accomplished without it.</p>
</dd>
<dt>Solution:</dt>
<dd>
<p>The preferred approach uses a
<code class="directive"><a href="../mod/mod_alias.html#redirect">Redirect</a></code> directive in a
dedicated HTTP virtual host:</p>
<pre class="prettyprint lang-config"><VirtualHost *:80>
ServerName www.example.com
Redirect permanent "/" "https://www.example.com/"
</VirtualHost>
<VirtualHost *:443>
ServerName www.example.com
# ... SSL configuration goes here
</VirtualHost></pre>
</dd>
<dt>Discussion:</dt>
<dd>
<p>If you do not have access to the main server configuration and
must use a <code>.htaccess</code> file, <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>
is the appropriate tool:</p>
<pre class="prettyprint lang-config">RewriteEngine On
RewriteCond "%{HTTPS}" !=on
RewriteRule "^(.*)" "https://%{SERVER_NAME}$1" [R=301,L]</pre>
<p>The <code>%{HTTPS}</code> variable is set to <code>on</code>
when the connection is using SSL/TLS, and is empty or
<code>off</code> otherwise. Using <code>R=301</code> issues a
permanent redirect, which tells search engines to update their
index.</p>
<p>See also the <a href="avoid.html#redirect">When not to use
mod_rewrite</a> document for more discussion of the
<code>Redirect</code> approach.</p>
<div class="note"><h3>Behind a load balancer or SSL terminator</h3>
<p>The <code>%{HTTPS}</code> variable is not a general-purpose
environment variable — it queries <code class="module"><a href="../mod/mod_ssl.html">mod_ssl</a></code>
directly. If SSL/TLS is terminated at an upstream load balancer
or reverse proxy, <code class="module"><a href="../mod/mod_ssl.html">mod_ssl</a></code> is not handling the
connection and <code>%{HTTPS}</code> will always report
<code>off</code>, even when the original client connected over
HTTPS.</p>
<p>In this situation, check the header set by the upstream proxy
instead. Most load balancers set
<code>X-Forwarded-Proto</code>:</p>
</div>
<pre class="prettyprint lang-config">RewriteEngine On
RewriteCond "%{HTTP:X-Forwarded-Proto}" =http [NC]
RewriteRule "^(.*)" "https://%{SERVER_NAME}$1" [R=301,L]</pre>
<div class="warning">
<p>Only trust <code>X-Forwarded-Proto</code> if you control the
upstream proxy and it overwrites the header on every request. An
attacker can forge this header when connecting directly to your
server. Consider restricting access so that only your load
balancer can reach the backend, or use
<code class="module"><a href="../mod/mod_remoteip.html">mod_remoteip</a></code> to validate the source.</p>
</div>
</dd>
</dl>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif"></a></div>
<div class="section">
<h2 id="acme-exemption">Exempting ACME challenge requests from HTTPS redirect <a title="Permanent link" href="#acme-exemption" class="permalink">¶</a></h2>
<dl>
<dt>Description:</dt>
<dd>
<p>You have forced all traffic to HTTPS (as above), but your
ACME client (Let's Encrypt, Certbot, etc.) needs plain HTTP
access to <code>/.well-known/acme-challenge/</code> to complete
domain validation.</p>
</dd>
<dt>Solution:</dt>
<dd>
<p>Place an exception <em>before</em> your HTTPS redirect
rule:</p>
<pre class="prettyprint lang-config">RewriteEngine On
RewriteRule "^/\.well-known/acme-challenge/" - [L]
RewriteCond "%{HTTPS}" !=on
RewriteRule "^(.*)" "https://%{SERVER_NAME}$1" [R=301,L]</pre>
</dd>
<dt>Discussion:</dt>
<dd>
<p>The dash (<code>-</code>) substitution means "do not rewrite."
Combined with <code>[L]</code>, it stops rule processing for any
request matching the ACME challenge path, allowing it to be
served over plain HTTP. All other requests continue to the
next rule and are redirected to HTTPS as usual.</p>
<p>If you are using the <code class="directive"><a href="../mod/mod_alias.html#redirect">Redirect</a></code> approach in a dedicated
port-80 VirtualHost, use an
<code class="directive"><a href="../mod/mod_alias.html#alias">Alias</a></code> and
<code class="directive"><a href="../mod/mod_alias.html#redirectmatch">RedirectMatch</a></code>
instead:</p>
<pre class="prettyprint lang-config"><VirtualHost *:80>
ServerName www.example.com
# Allow ACME challenges over HTTP
Alias "/.well-known/acme-challenge/" "/var/www/acme/.well-known/acme-challenge/"
<Directory "/var/www/acme/.well-known/acme-challenge">
Require all granted
</Directory>
# Everything else goes to HTTPS
RedirectMatch permanent "^/(?!\.well-known/acme-challenge/)(.*)$" "https://www.example.com/$1"
</VirtualHost></pre>
</dd>
</dl>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif"></a></div>
<div class="section">
<h2 id="trailing-slash">Trailing Slash Normalization <a title="Permanent link" href="#trailing-slash" class="permalink">¶</a></h2>
<dl>
<dt>Description:</dt>
<dd>
<p>You want to ensure that URLs for directories always end with
a trailing slash, or conversely, that they never do. This is a
common requirement for SEO and for consistent URL handling by
web applications.</p>
</dd>
<dt>Solution:</dt>
<dd>
<p>To add a trailing slash to URLs that map to directories:</p>
<pre class="prettyprint lang-config">RewriteCond "%{REQUEST_FILENAME}" -d
RewriteCond "%{REQUEST_URI}" "!/$"
RewriteRule "^(.*)$" "$1/" [R=301,L]</pre>
<p>To remove a trailing slash (except for actual directories):</p>
<pre class="prettyprint lang-config">RewriteCond "%{REQUEST_FILENAME}" !-d
RewriteCond "%{REQUEST_URI}" "(.+)/$"
RewriteRule "^" "%1" [R=301,L]</pre>
</dd>
<dt>Discussion:</dt>
<dd>
<p>Apache's <code class="module"><a href="../mod/mod_dir.html">mod_dir</a></code> already handles trailing
slash redirects for real directories when
<code class="directive"><a href="../mod/mod_dir.html#directoryslash">DirectorySlash</a></code> is enabled
(the default). You only need a <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> rule
if you want to enforce trailing slash behavior for URLs that do
not correspond to actual directories on disk, or if you want to
remove trailing slashes.</p>
</dd>
</dl>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif"></a></div>
<div class="section">
<h2 id="front-controller">Front Controller / Application Routing <a title="Permanent link" href="#front-controller" class="permalink">¶</a></h2>
<p>Most modern web frameworks route all requests through a single
entry point (a "front controller"). The
<code class="directive"><a href="../mod/mod_dir.html#fallbackresource">FallbackResource</a></code> directive
handles this more simply and efficiently than
<code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>. See <a href="avoid.html#fallback-resource">When NOT to use mod_rewrite</a>
for the recommended approach.</p>
<p>If you genuinely need <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> for this (for
example, to add conditions beyond "file doesn't exist"), see the
<a href="htaccess.html#rewritebase">per-directory rewrites</a>
document for an annotated example that also demonstrates
<code class="directive"><a href="../mod/mod_rewrite.html#rewritebase">RewriteBase</a></code> usage.</p>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif"></a></div>
<div class="section">
<h2 id="old-to-new-extern">Rewriting From Old to New (external) <a title="Permanent link" href="#old-to-new-extern" class="permalink">¶</a></h2>
<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>
<pre class="prettyprint lang-config">RewriteEngine on
RewriteRule "^<strong>/foo</strong>\.html$" "<strong>bar</strong>.html" [<strong>R</strong>]</pre>
</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. <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> was used in that earlier
example in order to hide the redirect from the client:</p>
<pre class="prettyprint lang-config">Redirect "/foo.html" "/bar.html"</pre>
</dd>
</dl>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif"></a></div>
<div class="section">
<h2 id="movehomedirs">Resource Moved to Another Server <a title="Permanent link" href="#movehomedirs" class="permalink">¶</a></h2>
<dl>
<dt>Description:</dt>
<dd>
<p>If a resource has moved to another server, you may wish to have
URLs continue to work for a time on the old server while people
update their bookmarks.</p>
</dd>
<dt>Solution:</dt>
<dd>
<p>You can use <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> to redirect these URLs
to the new server, but you might also consider using the Redirect
or RedirectMatch directive.</p>
<pre class="prettyprint lang-config">#With mod_rewrite
RewriteEngine on
RewriteRule "^/docs/(.+)" "http://new.example.com/docs/$1" [R,L]</pre>
<pre class="prettyprint lang-config">#With RedirectMatch
RedirectMatch "^/docs/(.*)" "http://new.example.com/docs/$1"</pre>
<pre class="prettyprint lang-config">#With Redirect
Redirect "/docs/" "http://new.example.com/docs/"</pre>
</dd>
<dt>Discussion:</dt>
<dd>
<p>For simple redirections to another server, the
<code class="directive"><a href="../mod/mod_alias.html#redirect">Redirect</a></code> or
<code class="directive"><a href="../mod/mod_alias.html#redirectmatch">RedirectMatch</a></code> directives
are preferred, as they are simpler and more efficient.</p>
</dd>
</dl>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif"></a></div>
<div class="section">
<h2 id="backward-compatibility">Backward Compatibility for file extension change <a title="Permanent link" href="#backward-compatibility" class="permalink">¶</a></h2>
<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>The URL is rewritten from the old extension to the new
one only if the target file with the new extension exists
and the original file with the old extension does not.
Otherwise, the URL is left unchanged.</p>
<pre class="prettyprint lang-config"># backward compatibility ruleset for
# rewriting document.html to document.php
# when and only when document.php exists
<Directory "/var/www/htdocs">
RewriteEngine on
RewriteBase "/var/www/htdocs"
RewriteCond "$1.php" -f
RewriteCond "$1.html" !-f
RewriteRule "^(.*).html$" "$1.php"
</Directory></pre>
</dd>
<dt>Discussion</dt>
<dd>
<p>This example uses an often-overlooked feature of <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>,
by taking advantage of the order of execution of the ruleset. In
particular, <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> evaluates the left-hand-side of the
RewriteRule before it evaluates the RewriteCond directives.
Consequently, $1 is already defined by the time the RewriteCond
directives are evaluated. This allows us to test for the existence
of 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
<Directory> 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 <code class="directive"><a href="../mod/mod_rewrite.html#rewritebase">RewriteBase</a></code> directive to specify the
directory base that you're working in.</p>
</dd>
</dl>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif"></a></div>
<div class="section">
<h2 id="canonicalhost">Canonical Hostnames <a title="Permanent link" href="#canonicalhost" class="permalink">¶</a></h2>
<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>The very best way to solve this doesn't involve <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> at all,
but rather uses the <code class="directive"><a href="../mod/mod_alias.html#redirect">Redirect</a></code>
directive placed in a virtual host for the non-canonical
hostname(s).</p>
<pre class="prettyprint lang-config"><VirtualHost *:80>
ServerName undesired.example.com
ServerAlias example.com notthis.example.com
Redirect "/" "http://www.example.com/"
</VirtualHost>
<VirtualHost *:80>
ServerName www.example.com
</VirtualHost></pre>
<p>You can alternatively accomplish this using the
<code class="directive"><a href="../mod/core.html#if"><If></a></code>
directive: (<strong>2.4 and later</strong>)</p>
<pre class="prettyprint lang-config"><If "%{HTTP_HOST} != 'www.example.com'">
Redirect "/" "http://www.example.com/"
</If></pre>
<p>Or, for example, to redirect a portion of your site to HTTPS, you
might do the following:</p>
<pre class="prettyprint lang-config"><If "%{SERVER_PROTOCOL} != 'HTTPS'">
Redirect "/admin/" "https://www.example.com/admin/"
</If></pre>
<p>If, for whatever reason, you still want to use <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>
- if, for example, you need this to work with a larger set of RewriteRules -
you might use one of the recipes below.</p>
<p>For sites running on a port other than 80:</p>
<pre class="prettyprint lang-config">RewriteCond "%{HTTP_HOST}" "!^www\.example\.com" [NC]
RewriteCond "%{HTTP_HOST}" "!^$"
RewriteCond "%{SERVER_PORT}" "!^80$"
RewriteRule "^/?(.*)" "http://www.example.com:%{SERVER_PORT}/$1" [L,R,NE]</pre>
<p>And for a site running on port 80</p>
<pre class="prettyprint lang-config">RewriteCond "%{HTTP_HOST}" "!^www\.example\.com" [NC]
RewriteCond "%{HTTP_HOST}" "!^$"
RewriteRule "^/?(.*)" "http://www.example.com/$1" [L,R,NE]</pre>
<p>
If you wanted to do this generically for all domain names - that
is, if you want to redirect <strong>example.com</strong> to
<strong>www.example.com</strong> for all possible values of
<strong>example.com</strong>, you could use the following
recipe:</p>
<p>To do the reverse - strip the <code>www.</code> prefix - swap the
condition:</p>
<pre class="prettyprint lang-config">RewriteCond "%{HTTP_HOST}" "^www\.(.+)$" [NC]
RewriteRule "^(.*)" "http://%1/$1" [L,R,NE]</pre>
<p>To generically add <code>www.</code> to any hostname:</p>
<pre class="prettyprint lang-config">RewriteCond "%{HTTP_HOST}" "!^www\." [NC]
RewriteCond "%{HTTP_HOST}" "!^$"
RewriteRule "^/?(.*)" "http://www.%{HTTP_HOST}/$1" [L,R,NE]</pre>
<p>These rulesets will work either in your main server configuration
file, or in a <code>.htaccess</code> file placed in the <code class="directive"><a href="../mod/core.html#documentroot">DocumentRoot</a></code> of the server.</p>
</dd>
<dt>Discussion:</dt>
<dd>
<p>If you have access to the server configuration, a
<code class="directive"><a href="../mod/mod_alias.html#redirect">Redirect</a></code> in a dedicated
<code class="directive"><a href="../mod/core.html#virtualhost"><VirtualHost></a></code>
is the cleanest approach. Canonicalizing the hostname ensures that
search engines treat your site as a single entity and avoids
cookie scope issues that arise when the same site is reachable
under multiple names.</p>
<p>Use the
<code class="directive"><a href="../mod/core.html#if"><If></a></code> directive
as a middle ground, and <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> only if you
are limited to <code>.htaccess</code>.</p>
</dd>
</dl>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif"></a></div>
<div class="section">
<h2 id="multipledirs">Search for pages in more than one directory <a title="Permanent link" href="#multipledirs" class="permalink">¶</a></h2>
<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>
<pre class="prettyprint lang-config">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>
</dd>
<dt>Discussion:</dt>
<dd>
<p>This is useful during migrations when content is being moved
between directories. For permanent setups, consider using
<code class="directive"><a href="../mod/mod_alias.html#alias">Alias</a></code> or symbolic links
instead.</p>
</dd>
</dl>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif"></a></div>
<div class="section">
<h2 id="canonicalurl">Canonical URLs <a title="Permanent link" href="#canonicalurl" class="permalink">¶</a></h2>
<dl>
<dt>Description:</dt>
<dd>
<p>On some webservers there is more than one URL for a
resource. Usually there are canonical URLs (which are be
actually used and distributed) and those which are just
shortcuts, internal ones, and so on. Independent of which URL the
user supplied with the request, they should finally see the
canonical one in their browser address bar.</p>
</dd>
<dt>Solution:</dt>
<dd>
<p>We do an external HTTP redirect for all non-canonical
URLs to fix them in the location view of the Browser and
for all subsequent requests. In the example ruleset below
we replace <code>/puppies</code> and <code>/canines</code>
by the canonical <code>/dogs</code>.</p>
<pre class="prettyprint lang-config">RewriteRule "^/(puppies|canines)/(.*)" "/dogs/$2" [R]</pre>
</dd>
<dt>Discussion:</dt>
<dd>
This should really be accomplished with Redirect or RedirectMatch
directives:
<pre class="prettyprint lang-config">RedirectMatch "^/(puppies|canines)/(.*)" "/dogs/$2"</pre>
</dd>
</dl>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif"></a></div>
<div class="section">
<h2 id="moveddocroot">Moved <code>DocumentRoot</code> <a title="Permanent link" href="#moveddocroot" class="permalink">¶</a></h2>
<dl>
<dt>Description:</dt>
<dd>
<p>Usually the <code class="directive"><a href="../mod/core.html#documentroot">DocumentRoot</a></code>
of the webserver directly relates to the URL "<code>/</code>".
But often this data is not really of top-level priority. For example,
you may wish for visitors, on first entering a site, to go to a
particular subdirectory <code>/about/</code>. This may be accomplished
using the following ruleset:</p>
</dd>
<dt>Solution:</dt>
<dd>
<p>We redirect the URL <code>/</code> to
<code>/about/</code>:
</p>
<pre class="prettyprint lang-config">RewriteEngine on
RewriteRule "^/$" "/about/" [<strong>R</strong>]</pre>
<p>Note that this can also be handled using the <code class="directive"><a href="../mod/mod_alias.html#redirectmatch">RedirectMatch</a></code> directive:</p>
<pre class="prettyprint lang-config">RedirectMatch "^/$" "http://example.com/about/"</pre>
<p>Note also that the example rewrites only the root URL. That is, it
rewrites a request for <code>http://example.com/</code>, but not a
request for <code>http://example.com/page.html</code>. If you have in
fact changed your document root - that is, if <strong>all</strong> of
your content is in fact in that subdirectory, it is greatly preferable
to simply change your <code class="directive"><a href="../mod/core.html#documentroot">DocumentRoot</a></code>
directive, or move all of the content up one directory,
rather than rewriting URLs.</p>
</dd>
</dl>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif"></a></div>
<div class="section">
<h2 id="rewrite-query">Rewrite query string <a title="Permanent link" href="#rewrite-query" class="permalink">¶</a></h2>
<dl>
<dt>Description:</dt>
<dd>You want to capture a particular value from a query string
and either replace it or incorporate it into another component
of the URL.</dd>
<dt>Solutions:</dt>
<dd>
<p> Many of the solutions in this section will all use the same condition,
which leaves the matched value in the %2 backreference. %1 is the beginning
of the query string (up to the key of intererest), and %3 is the remainder. This
condition is a bit complex for flexibility and to avoid double '&&' in the
substitutions.</p>
<ul>
<li>This solution removes the matching key and value:
<pre class="prettyprint lang-config"># Remove mykey=???
RewriteCond "%{QUERY_STRING}" "(.*(?:^|&))mykey=([^&]*)&?(.*)&?$"
RewriteRule "(.*)" "$1?%1%3"</pre>
</li>
<li>This solution uses the captured value in the URL substitution,
discarding the rest of the original query by appending a '?':
<pre class="prettyprint lang-config"># Copy from query string to PATH_INFO
RewriteCond "%{QUERY_STRING}" "(.*(?:^|&))mykey=([^&]*)&?(.*)&?$"
RewriteRule "(.*)" "$1/products/%2/?" [PT]</pre>
</li>
<li>This solution checks the captured value in a subsequent condition:
<pre class="prettyprint lang-config"># Capture the value of mykey in the query string
RewriteCond "%{QUERY_STRING}" "(.*(?:^|&))mykey=([^&]*)&?(.*)&?$"
RewriteCond "%2" !=not-so-secret-value
RewriteRule "(.*)" "-" [F]</pre>
</li>
<li>This solution shows the reverse of the previous ones, copying
path components (perhaps <a class="glossarylink" href="../glossary.html#pathinfo" title="see glossary">PATH_INFO</a>) from the URL into the query string.
<pre class="prettyprint lang-config"># The desired URL might be /products/kitchen-sink, and the script expects
# /path?products=kitchen-sink.
RewriteRule "^/?path/([^/]+)/([^/]+)" "/path?$1=$2" [PT]</pre>
</li>
</ul>
</dd>
<dt>Discussion:</dt>
<dd>
<p>See also the <a href="flags.html#flag_qsa">[QSA]</a> and
<a href="flags.html#flag_qsd">[QSD]</a> flags, which control whether
the original query string is appended to or discarded from the
substitution.</p>
</dd>
</dl>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif"></a></div>
<div class="section">
<h2 id="structuredhomedirs">Structured Userdirs <a title="Permanent link" href="#structuredhomedirs" class="permalink">¶</a></h2>
<dl>
<dt>Description:</dt>
<dd>
<p>Some sites with thousands of users use a
structured homedir layout, <em>i.e.</em> each homedir is in a
subdirectory which begins (for instance) with the first
character of the username. So, <code>/~larry/anypath</code>
is <code>/home/<strong>l</strong>/larry/public_html/anypath</code>
while <code>/~waldo/anypath</code> is
<code>/home/<strong>w</strong>/waldo/public_html/anypath</code>.</p>
</dd>
<dt>Solution:</dt>
<dd>
<p>We use the following ruleset to expand the tilde URLs
into the above layout.</p>
<pre class="prettyprint lang-config">RewriteEngine on
RewriteRule "^/~(<strong>([a-z])</strong>[a-z0-9]+)(.*)" "/home/<strong>$2</strong>/$1/public_html$3"</pre>
</dd>
<dt>Discussion:</dt>
<dd>
<p>This technique is primarily useful for large hosting
environments with thousands of users. For most sites,
<code class="module"><a href="../mod/mod_userdir.html">mod_userdir</a></code> handles tilde-based user URLs
without requiring <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>.</p>
</dd>
</dl>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif"></a></div>
<div class="section">
<h2 id="redirectanchors">Redirecting Anchors <a title="Permanent link" href="#redirectanchors" class="permalink">¶</a></h2>
<dl>
<dt>Description:</dt>
<dd>
<p>By default, redirecting to an HTML anchor doesn't work,
because <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> escapes the <code>#</code> character,
turning it into <code>%23</code>. This, in turn, breaks the
redirection.</p>
</dd>
<dt>Solution:</dt>
<dd>
<p>Use the <code>[NE]</code> flag on the
<code>RewriteRule</code>. NE stands for No Escape.
</p>
</dd>
<dt>Discussion:</dt>
<dd>This technique will of course also work with other
special characters that <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>, by default, URL-encodes.</dd>
</dl>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif"></a></div>
<div class="section">
<h2 id="time-dependent">Time-Dependent Rewriting <a title="Permanent link" href="#time-dependent" class="permalink">¶</a></h2>
<dl>
<dt>Description:</dt>
<dd>
<p>We wish to use <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> to serve different content based on
the time of day.</p>
</dd>
<dt>Solution:</dt>
<dd>
<p>There are a lot of variables named <code>TIME_xxx</code>
for rewrite conditions. In conjunction with the special
lexicographic comparison patterns <code><STRING</code>,
<code>>STRING</code> and <code>=STRING</code> we can
do time-dependent redirects:</p>
<pre class="prettyprint lang-config">RewriteEngine on
RewriteCond "%{TIME_HOUR}%{TIME_MIN}" >0700
RewriteCond "%{TIME_HOUR}%{TIME_MIN}" <1900
RewriteRule "^foo\.html$" "foo.day.html" [L]
RewriteRule "^foo\.html$" "foo.night.html"</pre>
<p>This provides the content of <code>foo.day.html</code>
under the URL <code>foo.html</code> from
<code>07:01-18:59</code> and at the remaining time the
contents of <code>foo.night.html</code>.</p>
<div class="warning"><code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code>, intermediate proxies
and browsers may each cache responses and cause the either page to be
shown outside of the time-window configured.
<code class="module"><a href="../mod/mod_expires.html">mod_expires</a></code> may be used to control this
effect. You are, of course, much better off simply serving the
content dynamically, and customizing it based on the time of day.</div>
</dd>
<dt>Discussion:</dt>
<dd>
<p>Serving dynamic content through your application is almost
always a better approach. Caching by browsers, proxies, and
<code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code> makes time-based rewriting unreliable
in practice.</p>
</dd>
</dl>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif"></a></div>
<div class="section">
<h2 id="on-the-fly-content">On-the-fly Content-Regeneration <a title="Permanent link" href="#on-the-fly-content" class="permalink">¶</a></h2>
<dl>
<dt>Description:</dt>
<dd>
<p>We wish to dynamically generate content, but store it
statically once it is generated. This rule will check for the
existence of the static file, and if it's not there, generate
it. The static files can be removed periodically, if desired (say,
via cron) and will be regenerated on demand.</p>
</dd>
<dt>Solution:</dt>
<dd>
This is done via the following ruleset:
<pre class="prettyprint lang-config"># This example is valid in per-directory context only
RewriteCond "%{REQUEST_URI}" !-U
RewriteRule "^(.+)\.html$" "/regenerate_page.cgi" [PT,L]</pre>
<p>The <code>-U</code> operator determines whether the test string
(in this case, <code>REQUEST_URI</code>) is a valid URL. It does
this via a subrequest. In the event that this subrequest fails -
that is, the requested resource doesn't exist - this rule invokes
the CGI program <code>/regenerate_page.cgi</code>, which generates
the requested resource and saves it into the document directory, so
that the next time it is requested, a static copy can be served.</p>
<p>In this way, documents that are infrequently updated can be served in
static form. if documents need to be refreshed, they can be deleted
from the document directory, and they will then be regenerated the
next time they are requested.</p>
</dd>
<dt>Discussion:</dt>
<dd>
<p>Modern approaches such as <code class="module"><a href="../mod/mod_cache.html">mod_cache</a></code>, CDN
caching layers, or application-level caching provide more robust
and controllable solutions for serving pre-generated static
content. The <code>-U</code> subrequest test used here also
carries a performance cost on every request.</p>
</dd>
</dl>
</div></div>
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