The RewriteEngine directive enables or disables the runtime rewriting engine. If it is set to off this module does no runtime processing at all. It does not even update the SCRIPT_URx environment variables.

Use this directive to disable the module instead of commenting out all the RewriteRule directives!

Note that rewrite configurations are not inherited by virtual hosts. This means that you need to have a RewriteEngine on directive for each virtual host in which you wish to use rewrite rules.

RewriteMap directives of the type prg are not started during server initialization if they're defined in a context that does not have RewriteEngine set to on

The RewriteOptions directive sets some special options for the current per-server or per-directory configuration. The Option string can currently only be one of the following:

inherit

This forces the current configuration to inherit the configuration of the parent. In per-virtual-server context, this means that the maps, conditions and rules of the main server are inherited. In per-directory context this means that conditions and rules of the parent directory's .htaccess configuration or Directory sections are inherited. The inherited rules are virtually copied to the section where this directive is being used. If used in combination with local rules, the inherited rules are copied behind the local rules. The position of this directive - below or above of local rules - has no influence on this behavior. If local rules forced the rewriting to stop, the inherited rules won't be processed.

The RewriteLog directive sets the name of the file to which the server logs any rewriting actions it performs. If the name does not begin with a slash ('/') then it is assumed to be relative to the Server Root. The directive should occur only once per server config.

The RewriteLogLevel directive sets the verbosity level of the rewriting logfile. The default level 0 means no logging, while 9 or more means that practically all actions are logged.

To disable the logging of rewriting actions simply set Level to 0. This disables all rewrite action logs.

This directive sets the filename for a synchronization lockfile which mod_rewrite needs to communicate with RewriteMap programs. Set this lockfile to a local path (not on a NFS-mounted device) when you want to use a rewriting map-program. It is not required for other types of rewriting maps.

The RewriteMap directive defines a Rewriting Map which can be used inside rule substitution strings by the mapping-functions to insert/substitute fields through a key lookup. The source of this lookup can be of various types.

The MapName is the name of the map and will be used to specify a mapping-function for the substitution strings of a rewriting rule via one of the following constructs:

${ MapName : LookupKey }
${ MapName : LookupKey | DefaultValue }

When such a construct occurs, the map MapName is consulted and the key LookupKey is looked-up. If the key is found, the map-function construct is substituted by SubstValue. If the key is not found then it is substituted by DefaultValue or by the empty string if no DefaultValue was specified.

For example, you might define a RewriteMap as:

You would then be able to use this map in a RewriteRule as follows:

The following combinations for MapType and MapSource can be used:

• Standard Plain Text
  MapType: txt, MapSource: Unix filesystem path to valid regular file

  This is the standard rewriting map feature where the MapSource is a plain ASCII file containing either blank lines, comment lines (starting with a '#' character) or pairs like the following - one per line.

  MatchingKey SubstValue

  ##
  ##  map.txt -- rewriting map
  ##
  
  Ralf.S.Engelschall    rse   # Bastard Operator From Hell
  Mr.Joe.Average        joe   # Mr. Average
  

  RewriteMap real-to-user txt:/path/to/file/map.txt
• Randomized Plain Text
  MapType: rnd, MapSource: Unix filesystem path to valid regular file

  This is identical to the Standard Plain Text variant above but with a special post-processing feature: After looking up a value it is parsed according to contained ``|'' characters which have the meaning of ``or''. In other words they indicate a set of alternatives from which the actual returned value is chosen randomly. For example, you might use the following map file and directives to provide a random load balancing between several back-end server, via a reverse-proxy. Images are sent to one of the servers in the 'static' pool, while everything else is sent to one of the 'dynamic' pool.

  Example:

  ##
  ##  map.txt -- rewriting map
  ##
  
  static   www1|www2|www3|www4
  dynamic  www5|www6
  

  RewriteMap servers rnd:/path/to/file/map.txt
  
  RewriteRule ^/(.*\.(png|gif|jpg)) http://${servers:static}/$1 [NC,P,L]
  RewriteRule ^/(.*) http://${servers:dynamic}/$1 [P,L]
• Hash File
  MapType: dbm[=type], MapSource: Unix filesystem path to valid regular file

  Here the source is a binary format DBM file containing the same contents as a Plain Text format file, but in a special representation which is optimized for really fast lookups. The type can be sdbm, gdbm, ndbm, or db depending on compile-time settings. If the type is omitted, the compile-time default will be chosen.

  To create a dbm file from a source text file, use the httxt2dbm utility.

  $ httxt2dbm -i mapfile.txt -o mapfile.map
• Internal Function
  MapType: int, MapSource: Internal Apache function

  Here, the source is an internal Apache function. Currently you cannot create your own, but the following functions already exist:

  • toupper:
    Converts the key to all upper case.
  • tolower:
    Converts the key to all lower case.
  • escape:
    Translates special characters in the key to hex-encodings.
  • unescape:
    Translates hex-encodings in the key back to special characters.
• External Rewriting Program
  MapType: prg, MapSource: Unix filesystem path to valid regular file

  Here the source is a program, not a map file. To create it you can use a language of your choice, but the result has to be an executable program (either object-code or a script with the magic cookie trick '#!/path/to/interpreter' as the first line).

  This program is started once, when the Apache server is started, and then communicates with the rewriting engine via its stdin and stdout file-handles. For each map-function lookup it will receive the key to lookup as a newline-terminated string on stdin. It then has to give back the looked-up value as a newline-terminated string on stdout or the four-character string ``NULL'' if it fails (i.e., there is no corresponding value for the given key).

  External rewriting programs are not started if they're defined in a context that does not have RewriteEngine set to on

  .

  A trivial program which will implement a 1:1 map (i.e., key == value) could be:

  #!/usr/bin/perl
  $| = 1;
  while (<STDIN>) {
      # ...put here any transformations or lookups...
      print $_;
  }
  

  But be very careful:

  1. ``Keep it simple, stupid'' (KISS). If this program hangs, it will cause Apache to hang when trying to use the relevant rewrite rule.
  2. A common mistake is to use buffered I/O on stdout. Avoid this, as it will cause a deadloop! ``$|=1'' is used above, to prevent this.
  3. The RewriteLock directive can be used to define a lockfile which mod_rewrite can use to synchronize communication with the mapping program. By default no such synchronization takes place.

• SQL Query
  MapType: dbd or fastdbd, MapSource: An SQL SELECT statement that takes a single argument and returns a single value.

  This uses mod_dbd to implement a rewritemap by lookup in an SQL database. There are two forms: fastdbd caches database lookups internally, dbd doesn't. So dbd incurs a performance penalty but responds immediately if the database contents are updated, while fastdbd is more efficient but won't re-read database contents until server restart.

  If a query returns more than one row, a random row from the result set is used.

  RewriteMap myquery "fastdbd:SELECT destination FROM rewrite WHERE source = %s"

The RewriteMap directive can occur more than once. For each mapping-function use one RewriteMap directive to declare its rewriting mapfile. While you cannot declare a map in per-directory context it is of course possible to use this map in per-directory context.

The RewriteBase directive explicitly sets the base URL for per-directory rewrites. When you use a RewriteRule in a .htaccess file, mod_rewrite strips off the local directory prefix before processing, then rewrites the rest of the URL. When the rewrite is completed, mod_rewrite automatically adds the local directory prefix back on to the path.

If your URL path does not exist on the filesystem, you must use RewriteBase in every .htaccess file where you want to use RewriteRule directives.

The example below demonstrates how to map http://example.com/foo/index.html to /home/www/example/newsite.html, in a .htaccess file. This assumes that the content available at http://example.com/ is on disk at /home/www/example/.

RewriteEngine On
RewriteBase /foo/
RewriteRule ^index\.html$  newsite.html

The RewriteCond directive defines a rule condition. One or more RewriteCond conditions can precede a RewriteRule directive. The following rewrite rule is then used only if these conditions are met, and if the URI matches the pattern specified in the rule.

RewriteCond  %{HTTP_USER_AGENT}  ^Mozilla.*
RewriteRule  ^/$                 /homepage.max.html  [L]

RewriteCond  %{HTTP_USER_AGENT}  ^Lynx.*
RewriteRule  ^/$                 /homepage.min.html  [L]

RewriteRule  ^/$                 /homepage.std.html  [L]

The RewriteRule directive is the real rewriting workhorse. The directive can occur more than once, with each instance defining a single rewrite rule. The order in which these rules are defined is important - this is the order in which they will be applied at run-time.

Pattern is a perl compatible regular expression. On the first RewriteRule it is applied to the (%-encoded) URL-path of the request; subsequent patterns are applied to the output of the last matched RewriteRule.

For some hints on regular expressions, see the mod_rewrite Introduction.

In mod_rewrite, the NOT character ('!') is also available as a possible pattern prefix. This enables you to negate a pattern; to say, for instance: ``if the current URL does NOT match this pattern''. This can be used for exceptional cases, where it is easier to match the negative pattern, or as a last default rule.

The Substitution of a rewrite rule is the string that replaces the original URL-path that was matched by Pattern. The Substitution may be a:

file-system path

Designates the location on the file-system of the resource to be delivered to the client.

URL-path

A DocumentRoot-relative path to the resource to be served. Note that mod_rewrite tries to guess whether you have specified a file-system path or a URL-path by checking to see if the first segment of the path exists at the root of the file-system. For example, if you specify a Substitution string of /www/file.html, then this will be treated as a URL-path unless a directory named www exists at the root or your file-system, in which case it will be treated as a file-system path. If you wish other URL-mapping directives (such as Alias) to be applied to the resulting URL-path, use the [PT] flag as described below.

Absolute URL

If an absolute URL is specified, mod_rewrite checks to see whether the hostname matches the current host. If it does, the scheme and hostname are stripped out and the resulting path is treated as a URL-path. Otherwise, an external redirect is performed for the given URL. To force an external redirect back to the current host, see the [R] flag below.

- (dash)

A dash indicates that no substitution should be performed (the existing path is passed through untouched). This is used when a flag (see below) needs to be applied without changing the path.

In addition to plain text, the Substition string can include

1. back-references ($N) to the RewriteRule pattern
2. back-references (%N) to the last matched RewriteCond pattern
3. server-variables as in rule condition test-strings (%{VARNAME})
4. mapping-function calls (${mapname:key|default})

Back-references are identifiers of the form $N (N=0..9), which will be replaced by the contents of the Nth group of the matched Pattern. The server-variables are the same as for the TestString of a RewriteCond directive. The mapping-functions come from the RewriteMap directive and are explained there. These three types of variables are expanded in the order above.

As already mentioned, all rewrite rules are applied to the Substitution (in the order in which they are defined in the config file). The URL is completely replaced by the Substitution and the rewriting process continues until all rules have been applied, or it is explicitly terminated by a L flag.

Additionally you can set special actions to be performed by appending [flags] as the third argument to the RewriteRule directive. Flags is a comma-separated list, surround by square brackets, of any of the following flags:

'B' (escape backreferences)

Apache has to unescape URLs before mapping them, so backreferences will be unescaped at the time they are applied. Using the B flag, non-alphanumeric characters in backreferences will be escaped. For example, consider the rule:

RewriteRule ^(/.*)$ /index.php?show=$1

This will map /C++ to /index.php?show=/C++. But it will also map /C%2b%2b to /index.php?show=/C++, because the %2b has been unescaped. With the B flag, it will instead map to /index.php?show=/C%2b%2b.

This escaping is particularly necessary in a proxy situation, when the backend may break if presented with an unescaped URL.

'chain|C' (chained with next rule)

This flag chains the current rule with the next rule (which itself can be chained with the following rule, and so on). This has the following effect: if a rule matches, then processing continues as usual - the flag has no effect. If the rule does not match, then all following chained rules are skipped. For instance, it can be used to remove the ``.www'' part, inside a per-directory rule set, when you let an external redirect happen (where the ``.www'' part should not occur!).

'cookie|CO=NAME:VAL:domain[:lifetime[:path[:secure[:httponly]]]]' (set cookie)

This sets a cookie in the client's browser. The cookie's name is specified by NAME and the value is VAL. The domain field is the domain of the cookie, such as '.apache.org', the optional lifetime is the lifetime of the cookie in minutes (0 means expires at end of session), and the optional path is the path of the cookie. If secure is set to 'secure', 'true' or '1', the cookie is only transmitted via secured connections. If httponly is set to 'HttpOnly', 'true' or '1', the HttpOnly flag is used, making the cookie inaccessible to JavaScript code on browsers that support this feature.

'discardpathinfo|DPI' (discard PATH_INFO)

This flag is available from 2.2.12

In per-directory context, the URI each RewriteRule compares against is the concatenation of the current values of the URI and PATH_INFO.

The current URI can be the initial URI as requested by the client, the result of a previous round of mod_rewrite processing, or the result of a prior rule in the current round of mod_rewrite processing.

In contrast, the PATH_INFO that is appended to the URI before each rule reflects only the value of PATH_INFO before this round of mod_rewrite processing. As a consequence, if large portions of the URI are matched and copied into a substitution in multiple RewriteRule directives, without regard for which parts of the URI came from the current PATH_INFO, the final URI may have multiple copies of PATH_INFO appended to it.

Use this flag on any substitution where the PATH_INFO that resulted from the previous mapping of this request to the filesystem is not of interest. This flag permanently forgets the PATH_INFO established before this round of mod_rewrite processing began. PATH_INFO will not be recalculated until the current round of mod_rewrite processing completes. Subsequent rules during this round of processing will see only the direct result of substitutions, without any PATH_INFO appended.

'env|E=VAR:VAL' (set environment variable)

This forces an environment variable named VAR to be set to the value VAL, where VAL can contain regexp backreferences ($N and %N) which will be expanded. You can use this flag more than once, to set more than one variable. The variables can later be dereferenced in many situations, most commonly from within XSSI (via <!--#echo var="VAR"-->) or CGI ($ENV{'VAR'}). You can also dereference the variable in a later RewriteCond pattern, using %{ENV:VAR}. Use this to strip information from URLs, while maintaining a record of that information.

'forbidden|F' (force URL to be forbidden)

This forces the current URL to be forbidden - it immediately sends back a HTTP response of 403 (FORBIDDEN). Use this flag in conjunction with appropriate RewriteConds to conditionally block some URLs.

'gone|G' (force URL to be gone)

This forces the current URL to be gone - it immediately sends back a HTTP response of 410 (GONE). Use this flag to mark pages which no longer exist as gone.

'handler|H=Content-handler' (force Content handler)

Force the Content-handler of the target file to be Content-handler. For instance, this can be used to simulate the mod_alias directive ScriptAlias, which internally forces all files inside the mapped directory to have a handler of ``cgi-script''.
If used in per-directory context, there must not be a substitution which changes the path. Use this flag in per-directory context only with - (dash) as the substitution, otherwise the request will fail.

'last|L' (last rule)

Stop the rewriting process here and don't apply any more rewrite rules. This corresponds to the Perl last command or the break command in C. Use this flag to prevent the currently rewritten URL from being rewritten further by following rules. Remember, however, that if the RewriteRule generates an internal redirect (which frequently occurs when rewriting in a per-directory context), this will reinject the request and will cause processing to be repeated starting from the first RewriteRule.

'next|N' (next round)

Re-run the rewriting process (starting again with the first rewriting rule). This time, the URL to match is no longer the original URL, but rather the URL returned by the last rewriting rule. This corresponds to the Perl next command or the continue command in C. Use this flag to restart the rewriting process - to immediately go to the top of the loop. Be careful not to create an infinite loop!

'nocase|NC' (no case)

This makes the Pattern case-insensitive, ignoring difference between 'A-Z' and 'a-z' when Pattern is matched against the current URL.

'noescape|NE' (no URI escaping of output)

This flag prevents mod_rewrite from applying the usual URI escaping rules to the result of a rewrite. Ordinarily, special characters (such as '%', '$', ';', and so on) will be escaped into their hexcode equivalents ('%25', '%24', and '%3B', respectively); this flag prevents this from happening. This allows percent symbols to appear in the output, as in RewriteRule ^/foo/(.*) /bar?arg=P1\%3d$1 [R,NE] which would turn '/foo/zed' into a safe request for '/bar?arg=P1=zed'.

'nosubreq|NS' (not for internal sub-requests)

This flag forces the rewriting engine to skip a rewriting rule if the current request is an internal sub-request. For instance, sub-requests occur internally in Apache when mod_dir tries to find out information about possible directory default files (index.xxx files). On sub-requests it is not always useful, and can even cause errors, if the complete set of rules are applied. Use this flag to exclude some rules.

To decide whether or not to use this rule: if you prefix URLs with CGI-scripts, to force them to be processed by the CGI-script, it's likely that you will run into problems (or significant overhead) on sub-requests. In these cases, use this flag.

'proxy|P' (force proxy)

This flag forces the substitution part to be internally sent as a proxy request and immediately (rewrite processing stops here) put through the proxy module. You must make sure that the substitution string is a valid URI (typically starting with http://hostname) which can be handled by the Apache proxy module. If not, you will get an error from the proxy module. Use this flag to achieve a more powerful implementation of the ProxyPass directive, to map remote content into the namespace of the local server.

Note: mod_proxy must be enabled in order to use this flag.

'passthrough|PT' (pass through to next handler)

This flag forces the rewrite engine to set the uri field of the internal request_rec structure to the value of the filename field. This flag is just a hack to enable post-processing of the output of RewriteRule directives, using Alias, ScriptAlias, Redirect, and other directives from various URI-to-filename translators. For example, to rewrite /abc to /def using mod_rewrite, and then /def to /ghi using mod_alias: RewriteRule ^/abc(.*) /def$1 [PT]
Alias /def /ghi If you omit the PT flag, mod_rewrite will rewrite uri=/abc/... to filename=/def/... as a full API-compliant URI-to-filename translator should do. Then mod_alias will try to do a URI-to-filename transition, which will fail.

Note: You must use this flag if you want to mix directives from different modules which allow URL-to-filename translators. The typical example is the use of mod_alias and mod_rewrite.

The PT flag implies the L flag: rewriting will be stopped in order to pass the request to the next phase of processing.

'qsappend|QSA' (query string append)

This flag forces the rewrite engine to append the query string part of the substitution string to the existing query string, instead of replacing it. Use this when you want to add more data to the query string via a rewrite rule. This rule has no net effect unless your substitution explicitly provides a new query string.

'redirect|R [=code]' (force redirect)

Prefix Substitution with http://thishost[:thisport]/ (which makes the new URL a URI) to force a external redirection. If no code is given, a HTTP response of 302 (MOVED TEMPORARILY) will be returned. If you want to use other response codes, simply specify the appropriate number or use one of the following symbolic names: temp (default), permanent, seeother. Use this for rules to canonicalize the URL and return it to the client - to translate ``/~'' into ``/u/'', or to always append a slash to /u/user, etc.
Note: When you use this flag, make sure that the substitution field is a valid URL! Otherwise, you will be redirecting to an invalid location. Remember that this flag on its own will only prepend http://thishost[:thisport]/ to the URL, and rewriting will continue. Usually, you will want to stop rewriting at this point, and redirect immediately. To stop rewriting, you should add the 'L' flag.

While this is typically used for redirects, any valid status code can be given here. If the status code is outside the redirect range (300-399), then the Substitution string is dropped and rewriting is stopped as if the L flag was used.

'skip|S=num' (skip next rule(s))

This flag forces the rewriting engine to skip the next num rules in sequence, if the current rule matches. Use this to make pseudo if-then-else constructs: The last rule of the then-clause becomes skip=N, where N is the number of rules in the else-clause. (This is not the same as the 'chain|C' flag!)

'type|T=MIME-type' (force MIME type)

Force the MIME-type of the target file to be MIME-type. This can be used to set up the content-type based on some conditions. If used in per-directory context, use only - (dash) as the substitution, otherwise the MIME-type set with this flag is lost due to an internal re-processing.

Here are all possible substitution combinations and their meanings:

Inside per-server configuration (httpd.conf)
for request ``GET /somepath/pathinfo'':

Given Rule                                      Resulting Substitution
----------------------------------------------  ----------------------------------
^/somepath(.*) otherpath$1                      invalid, not supported

^/somepath(.*) otherpath$1  [R]                 invalid, not supported

^/somepath(.*) otherpath$1  [P]                 invalid, not supported
----------------------------------------------  ----------------------------------
^/somepath(.*) /otherpath$1                     /otherpath/pathinfo

^/somepath(.*) /otherpath$1 [R]                 http://thishost/otherpath/pathinfo
                                                via external redirection

^/somepath(.*) /otherpath$1 [P]                 doesn't make sense, not supported
----------------------------------------------  ----------------------------------
^/somepath(.*) http://thishost/otherpath$1      /otherpath/pathinfo

^/somepath(.*) http://thishost/otherpath$1 [R]  http://thishost/otherpath/pathinfo
                                                via external redirection

^/somepath(.*) http://thishost/otherpath$1 [P]  doesn't make sense, not supported
----------------------------------------------  ----------------------------------
^/somepath(.*) http://otherhost/otherpath$1     http://otherhost/otherpath/pathinfo
                                                via external redirection

^/somepath(.*) http://otherhost/otherpath$1 [R] http://otherhost/otherpath/pathinfo
                                                via external redirection
                                                (the [R] flag is redundant)

^/somepath(.*) http://otherhost/otherpath$1 [P] http://otherhost/otherpath/pathinfo
                                                via internal proxy

Inside per-directory configuration for /somepath
(/physical/path/to/somepath/.htacccess, with RewriteBase /somepath)
for request ``GET /somepath/localpath/pathinfo'':

Given Rule                                      Resulting Substitution
----------------------------------------------  ----------------------------------
^localpath(.*) otherpath$1                      /somepath/otherpath/pathinfo

^localpath(.*) otherpath$1  [R]                 http://thishost/somepath/otherpath/pathinfo
                                                via external redirection

^localpath(.*) otherpath$1  [P]                 doesn't make sense, not supported
----------------------------------------------  ----------------------------------
^localpath(.*) /otherpath$1                     /otherpath/pathinfo

^localpath(.*) /otherpath$1 [R]                 http://thishost/otherpath/pathinfo
                                                via external redirection

^localpath(.*) /otherpath$1 [P]                 doesn't make sense, not supported
----------------------------------------------  ----------------------------------
^localpath(.*) http://thishost/otherpath$1      /otherpath/pathinfo

^localpath(.*) http://thishost/otherpath$1 [R]  http://thishost/otherpath/pathinfo
                                                via external redirection

^localpath(.*) http://thishost/otherpath$1 [P]  doesn't make sense, not supported
----------------------------------------------  ----------------------------------
^localpath(.*) http://otherhost/otherpath$1     http://otherhost/otherpath/pathinfo
                                                via external redirection

^localpath(.*) http://otherhost/otherpath$1 [R] http://otherhost/otherpath/pathinfo
                                                via external redirection
                                                (the [R] flag is redundant)

^localpath(.*) http://otherhost/otherpath$1 [P] http://otherhost/otherpath/pathinfo
                                                via internal proxy