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<title>Apache mod_rewrite Flags</title>

<summary>

<p>This document discusses the flags which are available to the

<directive module="mod_rewrite">RewriteRule</directive> directive,

providing more detailed explanations and examples of each.</p>

</summary>

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

<seealso><a href="rewrite_tech.html">Technical details</a></seealso>

<seealso><a href="rewrite_guide.html">Rewrite Guide - useful examples</a></seealso>

<seealso><a href="rewrite_guide_advanced.html">Advanced Rewrite Guide -

advanced useful examples</a></seealso>

<section id="introduction"><title>Introduction</title>

<p><directive module="mod_rewrite">RewriteRule</directive>s can have

their behavior modified by one or more flags. Flags are included in

square brackets at the end of the rule, and multiple flags are separated

by commas.</p>

<example>

RewriteRule pattern target [Flag1,Flag2,Flag3]

</example>

<p>The flags all have a short form, such as <code>CO</code>, as well as

a longer form, such as <code>cookie</code>. Some flags take one or more

arguments. Flags are not case sensitive.</p>

</section>

<section id="flags"><title>The flags</title>

<p>Each flag has a long and short form. While it is most common to use

the short form, it is recommended that you familiarize yourself with the

long form, so that you remember what each flag is supposed to do.</p>

<p>Presented here are each of the available flags, along with an example

of how you might use them.</p>

<section id="flag_c"><title>C|chain</title>

<p>The [C] or [chain] flag indicates that the <directive

module="mod_rewrite">RewriteRule</directive> is chained to the next

rule. That is, if the rule matches, then it is processed as usual and

control moves on to the next rule. However, if it does not match, then

the next rule, and any other rules that are chained together, will be

skipped.</p>

</section>

<section id="flag_co"><title>CO|cookie</title>

<p>The [CO], or [cookie] flag, allows you to set a cookie when a

particular <directive module="mod_rewrite">RewriteRule</directive>

matches. The argument consists of three required fields and two optional

fields.</p>

<p>You must declare a name and value for the cookie to be set, and the

domain for which you wish the cookie to be valid. You may optionally set

the lifetime of the cookie, and the path for which it should be

returned.</p>

<p>By default, the lifetime of the cookie is the current browser

session.</p>

<p>By default, the path for which the cookie will be valid is "/" - that

is, the entire website.</p>

<p>Several examples are offered here:</p>

<example>

RewriteEngine On<br />

RewriteRule ^/index.html - [CO=frontdoor:yes:.apache.org:1440:/]

</example>

<p>This rule doesn't rewrite the request (the "-" rewrite target tells

mod_rewrite to pass the request through unchanged) but sets a cookie

called 'frontdoor' to a value of 'yes'. The cookie is valid for any host

in the <code>.apache.org</code> domain. It will be set to expire in 1440

minutes (24 hours) and will be returned for all URIs.</p>

</section>

<section id="flag_e"><title>E|env</title>

<p>With the [E], or [env] flag, you can set the value of an environment

variable. Note that some environment variables may be set after the rule

is run, thus unsetting what you have set. See <a href="/env.html">the

Environment Variables document</a> for more details on how Environment

variables work.</p>

<p>The following example sets an evironment variable called 'image' to a

value of '1' if the requested URI is an image file. Then, that

environment variable is used to exclude those requests from the access

log.</p>

<example>

RewriteRule \.(png|gif|jpg) - [E=image:1]<br />

CustomLog logs/access_log combined env=!image

</example>

<p>Note that this same effect can be obtained using <directive

module="mod_setenvif">SetEnvIf</directive>. This technique is offered as

an example, not as a recommendation.</p>

</section>

<section id="flag_f"><title>F|forbidden</title>

<p>Using the [F] flag causes Apache to return a 403 Forbidden status

code to the client. While the same behavior can be accomplished using

the <directive module="mod_access">Deny</directive> directive, this

allows more flexibility in assigning a Forbidden status.</p>

<p>The following rule will forbid <code>.exe</code> files from being

downloaded from your server.</p>

<example>

RewriteRule \.exe - [F]

</example>

<p>This example uses the "-" syntax for the rewrite target, which means

that the requested URI is not modified.</p>

</section>

<section id="flag_g"><title>G|gone</title>

<p>The [G] flag forces Apache to return a 410 Gone status with the

response. This indicates that a resource used to be available, but is no

longer available.</p>

</section>

<section id="flag_h"><title>H|handler</title>

<p>Forces the resulting request to be handled with the specified

handler. For example, one might use this to force all files without a

file extension to be parsed by the php handler:</p>

<example>

RewriteRule !\. - [H=application/x-httpd-php]

</example>

<p>

The regular expression above - <code>!\.</code> - will match any request

that does not contain the literal <code>.</code> character.

</p>

</section>

<section id="flag_l"><title>L|last</title>

<p>The [L] flag causes <module>mod_rewrite</module> to stop processing

the rule set. In most contexts, this means that if the rule matches, no

further rules will be processed.</p>

<p>If you are using <directive

module="mod_rewrite">RewriteRule</directive> in either

<code>.htaccess</code> files or in

<directive type="section" module="core">Directory</directive> sections,

it is important to have some understanding of how the rules are

processed. The simplified form of this is that once the rules have been

processed, the rewritten request is handed back to the URL parsing

engine to do what it may with it. It is possible that as the rewritten

request is handled, the <code>.htaccess</code> file or

<directive type="section" module="core">Directory</directive> section

may be encountered again, and thus the ruleset may be run again from the

start. Most commonly this will happen if one of the rules causes a

redirect - either internal or external - causing the request process to

start over.</p>

<p>It is therefore important, if you are using <directive

module="mod_rewrite">RewriteRule</directive> directives in one of these

context that you take explicit steps to avoid rules looping, and not

count solely on the [L] flag to terminate execution of a series of

rules.</p>

</section>

<section id="flag_n"><title>N|next</title>

<p>

The [N] flag causes the ruleset to start over again from the top. Use

with extreme caution, as it may result in loop.

</p>

<p>

The [Next] flag could be used, for example, if you wished to replace a

certain string or letter repeatedly in a request.

</p>

</section>

<section id="flag_nc"><title>NC|nocase</title>

<p>Use of the [NC] flag causes the <directive

module="mod_rewrite">RewriteRule</directive> to be matched in a

case-insensitive manner. That is, it doesn't care whether letters appear

as upper-case or lower-case in the matched URI.</p>

<p>In the example below, any request for an image file will be proxied

to your dedicated image server. The match is case-insensitive, so that

<code>.jpg</code> and <code>.JPG</code> files are both acceptable, for

example.</p>

<example>

RewriteRule (.*\.(jpg|gif|png))$ http://images.example.com$1 [P,NC]

</example>

</section>

<section id="flag_ne"><title>NE|noescape</title>

<p>By default, special characters, such as <code>&amp;</code> and

<code>?</code>, for example, will be converted to their hexcode

equivalent. Using the [NE] flag prevents that from happening.

</p>

<example>

RewriteRule ^/anchor/(.+) /bigpage.html#$1 [NE,R]

</example>

<p>

The above example will redirect <code>/anchor/xyz</code> to

<code>/bigpage.html#xyz</code>. Omitting the [NE] will result in the #

being converted to its hexcode equivalent, <code>%23</code>.

</p>

</section>

<section id="flag_ns"><title>NS|nosubreq</title>

<p>Use of the [NS] flag prevents the rule from being used on

subrequests. For example, a page which is included using an SSI (Server

Side Include) is a subrequest, and you may want to avoid rewrites

happening on those subrequests.</p>

<p>

Images, javascript files, or css files, loaded as part of an HTML page,

are not subrequests - the browser requests them as separate HTTP

requests.

</p>

</section>

<section id="flag_p"><title>P|proxy</title>

<p>Use of the [P] flag causes the request to be handled by

<module>mod_proxy</module>, and handled via a proxy request. For

example, if you wanted all image requests to be handled by a back-end

image server, you might do something like the following:</p>

<example>

RewriteRule (.*)\.(jpg|gif|png) http://images.example.com$1.$2 [P]

</example>

<p>Use of the [P] flag implies [L] - that is, the request is immediatly

pushed through the proxy, and any following rules will not be

considered.</p>

</section>

<section id="flag_pt"><title>PT|passthrough</title>

<p>

The target (or substitution string) in a RewriteRule is assumed to be a

file path, by default. The use of the [PT] flag causes it to be trated

as a URI instead. That is to say, the

use of the [PT] flag causes the result of the <directive

module="mod_rewrite">RewriteRule</directive> to be passed back through

URL mapping, so that location-based mappings, such as <directive

module="mod_alias">Alias</directive>, for example, might have a chance to take

effect.

</p>

<p>

If, for example, you have an

<directive module="mod_alias">Alias</directive>

for /icons, and have a <directive

module="mod_rewrite">RewriteRule</directive> pointing there, you should

use the [PT] flag to ensure that the

<directive module="mod_alias">Alias</directive> is evaluated.

</p>

<example>

Alias /icons /usr/local/apache/icons

RewriteRule /pics/(.+)\.jpg /icons/$1.gif [PT]

</example>

<p>

Omission of the [PT] flag in this case will cause the Alias to be

ignored, resulting in a 'File not found' error being returned.

</p>

</section>

<section id="flag_qsa"><title>QSA|qsappend</title>

<p>

When the replacement URI contains a query string, the default behavior

of <directive module="mod_rewrite">RewriteRule</directive> is to discard

the existing query string, and replace it with the newly generated one.

Using the [QSA] flag causes the query strings to be combined.

</p>

<p>Consider the following rule:</p>

<example>

RewriteRule /pages/(.+) /page.php?page=$1 [QSA]

</example>

<p>With the [QSA] flag, a request for <code>/pages/123?one=two</code> will be

mapped to <code>/page.php?page=123&amp;one=two</code>. Without the [QSA]

flag, that same request will be mapped to

<code>/page.php?page=123</code> - that is, the existing query string

will be discarded.

</p>

</section>

<section id="flag_r"><title>R|redirect</title>

<p>

Use of the [R] flag causes a HTTP redirect to be issued to the browser.

If a fully-qualified URL is specified (that is, including

<code>http://servername/</code>) then a redirect will be issued to that

location. Otherwise, the current servername will be used to generate the

URL sent with the redirect.

</p>

<p>

A status code may be specified, in the range 300-399, with a 302 status

code being used by default if none is specified.

</p>

<p>

You will almost always want to use [R] in conjunction with [L] (that is,

use [R,L]) because on its own, the [R] flag prepends

<code>http://thishost[:thisport]</code> to the URI, but then passes this

on to the next rule in the ruleset, which can often result in 'Invalid

URI in request' warnings.

</p>

</section>

<section id="flag_s"><title>S|skip</title>

<p>The [S] flag is used to skip rules that you don't want to run. This

can be thought of as a <code>goto</code> statement in your rewrite

ruleset. In the following example, we only want to run the <directive

module="mod_rewrite">RewriteRule</directive> if the requested URI

doesn't correspond with an actual file.</p>

<example>

RewriteCond %{REQUEST_FILENAME} !-f<br />

RewriteCond %{REQUEST_FILENAME} !-d<br />

RewriteRule .? - [S=2]<br />

<br />

RewriteRule (.*\.gif) images.php?$1<br />

RewriteRule (.*\.html) docs.php?$1

</example>

<p>This technique is useful because a <directive

module="mod_rewrite">RewriteCond</directive> only applies to the

<directive module="mod_rewrite">RewriteRule</directive> immediately

following it. Thus, if you want to make a <code>RewriteCond</code> apply

to several <code>RewriteRule</code>s, one possible technique is to

negate those conditions and use a [Skip] flag.</p>

</section>

<section id="flag_t"><title>T|type</title>

<p>Sets the MIME type with which the resulting response will be

sent. This has the same effect as the <directive

module="mod_mime">AddType</directive> directive.</p>

<p>For example, you might use the following technique to serve Perl

source code as plain text, if requested in a particular way:</p>

<example>

# Files with 'IMG' in the name are gif images.

RewriteRule IMG - [T=image/gif]

</example>

<p>Please note that this is a trivial example, and could be better done

using <directive type="section" module="core">FilesMatch</directive>

instead. Always consider the alternate

solutions to a problem before resorting to rewrite, which will

invariably be a less efficient solution than the alternatives.</p>

</section>

</section>

</manualpage>