mod_rewrite
Provides a rule-based rewriting engine to rewrite requested URLs on the fly
Extension
mod_rewrite.c
rewrite_module

The mod_rewrite module uses a rule-based rewriting engine, based on a regular-expression parser, to rewrite requested URLs on the fly. By default, mod_rewrite maps a URL to a filesystem path. However, it can also be used to redirect one URL to another URL, or to invoke an internal proxy fetch.

mod_rewrite provides a flexible and powerful way to manipulate URLs using an unlimited number of rules. Each rule can have an unlimited number of attached rule conditions, to allow you to rewrite URL based on server variables, environment variables, HTTP headers, or time stamps.

mod_rewrite operates on the full URL path, including the path-info section. A rewrite rule can be invoked in `httpd.conf` or in `.htaccess`. The path generated by a rewrite rule can include a query string, or can lead to internal sub-processing, external request redirection, or internal proxy throughput.

Further details, discussion, and examples, are provided in the detailed mod_rewrite documentation.

# Logging

mod_rewrite offers detailed logging of its actions at the `trace1` to `trace8` log levels. The log level can be set specifically for mod_rewrite using the LogLevel directive: Up to level `debug`, no actions are logged, while `trace8` means that practically all actions are logged.

Using a high trace log level for mod_rewrite will slow down your Apache HTTP Server dramatically! Use a log level higher than `trace2` only for debugging!

## Example

LogLevel alert rewrite:trace3

## RewriteLog

Those familiar with earlier versions of mod_rewrite will no doubt be looking for the `RewriteLog` and `RewriteLogLevel` directives. This functionality has been completely replaced by the new per-module logging configuration mentioned above.

To get just the mod_rewrite-specific log messages, pipe the log file through grep:

tail -f error_log|fgrep '[rewrite:'

RewriteEngine
Enables or disables runtime rewriting engine
RewriteEngine on|off
RewriteEngine off
server config
virtual host
directory
.htaccess
FileInfo

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`

RewriteOptions
Sets some special options for the rewrite engine
RewriteOptions Options
server config
virtual host
directory
.htaccess
FileInfo
MaxRedirects
is no longer available in version 2.1 and later

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.

  Rules inherited from the parent scope are applied after rules specified in the child scope.

`InheritBefore`

  Like `Inherit` above, but the rules from the parent scope are applied before rules specified in the child scope. Available in Apache HTTP Server 2.3.10 and later.

`AllowNoSlash`

  By default, mod_rewrite will ignore URLs that map to a directory on disk but lack a trailing slash, in the expectation that the mod_dir module will issue the client with a redirect to the canonical URL with a trailing slash.

  When the DirectorySlash directive is set to off, the `AllowNoSlash` option can be enabled to ensure that rewrite rules are no longer ignored. This option makes it possible to apply rewrite rules within .htaccess files that match the directory without a trailing slash, if so desired. Available in Apache HTTP Server 2.4.0 and later.

RewriteMap
Defines a mapping function for key-lookup
RewriteMap MapName MapType:MapSource
server config
virtual host
The choice of different dbm types is available in Apache HTTP Server 2.0.41 and later

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. Empty values behave as if the key was absent, therefore it is not possible to distinguish between empty-valued keys and absent keys.

For example, you might define a RewriteMap as:

RewriteMap examplemap txt:/path/to/file/map.txt

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

RewriteRule ^/ex/(.*) ${examplemap:$1}

The following combinations for MapType and MapSource can be used:

txt
  A plain text file containing space-separated key-value pairs, one per line. (Details ...)
rnd
  Randomly selects an entry from a plain text file (Details ...)
dbm
  Looks up an entry in a dbm file containing name, value pairs. Hash is constructed from a plain text file format using the `httxt2dbm` utility. (Details ...)
int
  One of the four available internal functions provided by `RewriteMap`: toupper, tolower, escape or unescape. (Details ...)
prg
  Calls an external program or script to process the rewriting. (Details ...)
dbd or fastdbd
  A SQL SELECT statement to be performed to look up the rewrite target. (Details ...)

Further details, and numerous examples, may be found in the RewriteMap HowTo

RewriteBase
Sets the base URL for per-directory rewrites
RewriteBase URL-path
None
directory
.htaccess
FileInfo

The RewriteBase directive explicitly sets the base URL-path (not filesystem directory path!) for per-directory rewrites that result in the substitution of a relative path. 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 (or the RewriteBase when set) back on to the substitution before handing it back to the core of the server as if it were the original URL.

This directive is required for per-directory rewrites whose context is a directory made available via the Alias directive, when the substitution uses a relative path.

If your URL path does not exist verbatim on the filesystem, or isn't directly under your DocumentRoot, 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/myapp/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
    # The URL-path used to get to this context, not the filesystem path
    RewriteBase /myapp/
    RewriteRule ^index\.html$  newsite.html

RewriteCond
Defines a condition under which rewriting will take place
RewriteCond TestString CondPattern
server config
virtual host
directory
.htaccess
FileInfo

The RewriteCond directive defines a rule condition. One or more RewriteCond can precede a RewriteRule directive. The following rule is then only used if both the current state of the URI matches its pattern, and if these conditions are met.

TestString is a string which can contain the following expanded constructs in addition to plain text:

- RewriteRule backreferences: These are backreferences of the form `$N` (0 <= N <= 9). $1 to $9 provide access to the grouped parts (in parentheses) of the pattern, from the `RewriteRule` which is subject to the current set of `RewriteCond` conditions. $0 provides access to the whole string matched by that pattern.
- RewriteCond backreferences: These are backreferences of the form `%N` (0 <= N <= 9). %1 to %9 provide access to the grouped parts (again, in parentheses) of the pattern, from the last matched `RewriteCond` in the current set of conditions. %0 provides access to the whole string matched by that pattern.
- RewriteMap expansions: These are expansions of the form `${mapname:key|default}`. See the documentation for RewriteMap for more details.
- Server-Variables: These are variables of the form `%{` NAME_OF_VARIABLE `}` where NAME_OF_VARIABLE can be a string taken from the following list:

  HTTP headers: | connection & request: |
  --- | --- | ---
  HTTP_USER_AGENT HTTP_REFERER HTTP_COOKIE HTTP_FORWARDED HTTP_HOST HTTP_PROXY_CONNECTION HTTP_ACCEPT | REMOTE_ADDR REMOTE_HOST REMOTE_PORT REMOTE_USER REMOTE_IDENT REQUEST_METHOD SCRIPT_FILENAME PATH_INFO QUERY_STRING AUTH_TYPE |
  server internals: | date and time: | specials:
  DOCUMENT_ROOT SERVER_ADMIN SERVER_NAME SERVER_ADDR SERVER_PORT SERVER_PROTOCOL SERVER_SOFTWARE | TIME_YEAR TIME_MON TIME_DAY TIME_HOUR TIME_MIN TIME_SEC TIME_WDAY TIME | API_VERSION THE_REQUEST REQUEST_URI REQUEST_FILENAME IS_SUBREQ HTTPS REQUEST_SCHEME

  These variables all correspond to the similarly named HTTP MIME-headers, C variables of the Apache HTTP Server or `struct tm` fields of the Unix system. Most are documented elsewhere in the Manual or in the CGI specification.

  SERVER_NAME and SERVER_PORT depend on the values of UseCanonicalName and UseCanonicalPhysicalPort respectively.

  Those that are special to mod_rewrite include those below.

  `IS_SUBREQ`
    Will contain the text "true" if the request currently being processed is a sub-request, "false" otherwise. Sub-requests may be generated by modules that need to resolve additional files or URIs in order to complete their tasks.
  `API_VERSION`
    This is the version of the Apache httpd module API (the internal interface between server and module) in the current httpd build, as defined in include/ap_mmn.h. The module API version corresponds to the version of Apache httpd in use (in the release version of Apache httpd 1.3.14, for instance, it is 19990320:10), but is mainly of interest to module authors.
  `THE_REQUEST`
    The full HTTP request line sent by the browser to the server (e.g., "`GET /index.html HTTP/1.1`"). This does not include any additional headers sent by the browser. This value has not been unescaped (decoded), unlike most other variables below.
  `REQUEST_URI`
    The path component of the requested URI, such as "/index.html". This notably excludes the query string which is available as as its own variable named `QUERY_STRING`.
  `REQUEST_FILENAME`
    The full local filesystem path to the file or script matching the request, if this has already been determined by the server at the time `REQUEST_FILENAME` is referenced. Otherwise, such as when used in virtual host context, the same value as `REQUEST_URI`.
  `HTTPS`
    Will contain the text "on" if the connection is using SSL/TLS, or "off" otherwise. (This variable can be safely used regardless of whether or not mod_ssl is loaded).
  `REQUEST_SCHEME`
    Will contain the scheme of the request (ususally "http" or "https"). This value can be influenced with ServerName.

If the TestString has the special value `expr`, the CondPattern will be treated as a ap_expr.

Other things you should be aware of:

1. The variables SCRIPT_FILENAME and REQUEST_FILENAME contain the same value - the value of the `filename` field of the internal `request_rec` structure of the Apache HTTP Server. The first name is the commonly known CGI variable name while the second is the appropriate counterpart of REQUEST_URI (which contains the value of the `uri` field of `request_rec`).

   If a substitution occurred and the rewriting continues, the value of both variables will be updated accordingly.

   If used in per-server context (i.e., before the request is mapped to the filesystem) SCRIPT_FILENAME and REQUEST_FILENAME cannot contain the full local filesystem path since the path is unknown at this stage of processing. Both variables will initially contain the value of REQUEST_URI in that case. In order to obtain the full local filesystem path of the request in per-server context, use an URL-based look-ahead `%{LA-U:REQUEST_FILENAME}` to determine the final value of REQUEST_FILENAME.

2. `%{ENV:variable}`, where variable can be any environment variable, is also available. This is looked-up via internal Apache httpd structures and (if not found there) via `getenv()` from the Apache httpd server process.
3. `%{SSL:variable}`, where variable is the name of an SSL environment variable, can be used whether or not mod_ssl is loaded, but will always expand to the empty string if it is not. Example: `%{SSL:SSL_CIPHER_USEKEYSIZE}` may expand to `128`.
4. `%{HTTP:header}`, where header can be any HTTP MIME-header name, can always be used to obtain the value of a header sent in the HTTP request. Example: `%{HTTP:Proxy-Connection}` is the value of the HTTP header ```Proxy-Connection:`''.

   If a HTTP header is used in a condition this header is added to the Vary header of the response in case the condition evaluates to to true for the request. It is not added if the condition evaluates to false for the request. Adding the HTTP header to the Vary header of the response is needed for proper caching.

   It has to be kept in mind that conditions follow a short circuit logic in the case of the '`ornext|OR`' flag so that certain conditions might not be evaluated at all.

5. `%{LA-U:variable}` can be used for look-aheads which perform an internal (URL-based) sub-request to determine the final value of variable. This can be used to access variable for rewriting which is not available at the current stage, but will be set in a later phase.

   For instance, to rewrite according to the `REMOTE_USER` variable from within the per-server context (`httpd.conf` file) you must use `%{LA-U:REMOTE_USER}` - this variable is set by the authorization phases, which come after the URL translation phase (during which mod_rewrite operates).

   On the other hand, because mod_rewrite implements its per-directory context (`.htaccess` file) via the Fixup phase of the API and because the authorization phases come before this phase, you just can use `%{REMOTE_USER}` in that context.

6. `%{LA-F:variable}` can be used to perform an internal (filename-based) sub-request, to determine the final value of variable. Most of the time, this is the same as LA-U above.

CondPattern is the condition pattern, a regular expression which is applied to the current instance of the TestString. TestString is first evaluated, before being matched against CondPattern.

CondPattern is usually a perl compatible regular expression, but there is additional syntax available to perform other useful tests against the Teststring:

1. You can prefix the pattern string with a '`!`' character (exclamation mark) to specify a non-matching pattern.
2. You can perform lexicographical string comparisons:

   - '<CondPattern' (lexicographically precedes)
     Treats the CondPattern as a plain string and compares it lexicographically to TestString. True if TestString lexicographically precedes CondPattern.
   - '>CondPattern' (lexicographically follows)
     Treats the CondPattern as a plain string and compares it lexicographically to TestString. True if TestString lexicographically follows CondPattern.
   - '=CondPattern' (lexicographically equal)
     Treats the CondPattern as a plain string and compares it lexicographically to TestString. True if TestString is lexicographically equal to CondPattern (the two strings are exactly equal, character for character). If CondPattern is `""` (two quotation marks) this compares TestString to the empty string.
   - '<=CondPattern' (lexicographically less than or equal to)
     Treats the CondPattern as a plain string and compares it lexicographically to TestString. True if TestString lexicographically precedes CondPattern, or is equal to CondPattern (the two strings are equal, character for character).
   - '>=CondPattern' (lexicographically greater than or equal to)
     Treats the CondPattern as a plain string and compares it lexicographically to TestString. True if TestString lexicographically follows CondPattern, or is equal to CondPattern (the two strings are equal, character for character).
3. You can perform integer comparisons:
   - '-eq' (is numerically equal to)
     The TestString is treated as an integer, and is numerically compared to the CondPattern. True if the two are numerically equal.
   - '-ge' (is numerically greater than or equal to)
     The TestString is treated as an integer, and is numerically compared to the CondPattern. True if the TestString is numerically greater than or equal to the CondPattern.
   - '-gt' (is numerically greater than)
     The TestString is treated as an integer, and is numerically compared to the CondPattern. True if the TestString is numerically greater than the CondPattern.
   - '-le' (is numerically less than or equal to)
     The TestString is treated as an integer, and is numerically compared to the CondPattern. True if the TestString is numerically less than or equal to the CondPattern. Avoid confusion with the -l by using the -L or -h variant.
   - '-lt' (is numerically less than)
     The TestString is treated as an integer, and is numerically compared to the CondPattern. True if the TestString is numerically less than the CondPattern. Avoid confusion with the -l by using the -L or -h variant.
4. You can perform various file attribute tests:
   - '-d' (is directory)
     Treats the TestString as a pathname and tests whether or not it exists, and is a directory.
   - '-f' (is regular file)
     Treats the TestString as a pathname and tests whether or not it exists, and is a regular file.
   - '-F' (is existing file, via subrequest)
     Checks whether or not TestString is a valid file, accessible via all the server's currently-configured access controls for that path. This uses an internal subrequest to do the check, so use it with care - it can impact your server's performance!
   - '-H' (is symbolic link, bash convention)
     See -l.
   - '-l' (is symbolic link)
     Treats the TestString as a pathname and tests whether or not it exists, and is a symbolic link. May also use the bash convention of -L or -h if there's a possibility of confusion such as when using the -lt or -le tests.
   - '-L' (is symbolic link, bash convention)
     See -l.
   - '-s' (is regular file, with size)
     Treats the TestString as a pathname and tests whether or not it exists, and is a regular file with size greater than zero.
   - '-U' (is existing URL, via subrequest)
     Checks whether or not TestString is a valid URL, accessible via all the server's currently-configured access controls for that path. This uses an internal subrequest to do the check, so use it with care - it can impact your server's performance!
   - '-x' (has executable permissions)
     Treats the TestString as a pathname and tests whether or not it exists, and has executable permissions. These permissions are determined according to the underlying OS.

   # Note:

   All of these tests can also be prefixed by an exclamation mark ('!') to negate their meaning.

5. If the TestString has the special value `expr`, the CondPattern will be treated as a ap_expr.

   In the below example, `-strmatch` is used to compare the `REFERER` against the site hostname, to block unwanted hotlinking.

   RewriteCond expr "! %{HTTP_REFERER} -strmatch '*://%{HTTP_HOST}/*'"
   RewriteRule ^/images - [F]
6. You can also set special flags for CondPattern by appending `[`flags`]` as the third argument to the `RewriteCond` directive, where flags is a comma-separated list of any of the following flags:

   - '`nocase|NC`' (no case)
     This makes the test case-insensitive - differences between 'A-Z' and 'a-z' are ignored, both in the expanded TestString and the CondPattern. This flag is effective only for comparisons between TestString and CondPattern. It has no effect on filesystem and subrequest checks.
   - '`ornext|OR`' (or next condition)
     Use this to combine rule conditions with a local OR instead of the implicit AND. Typical example:

         RewriteCond %{REMOTE_HOST}  ^host1  [OR]
         RewriteCond %{REMOTE_HOST}  ^host2  [OR]
         RewriteCond %{REMOTE_HOST}  ^host3
         RewriteRule ...some special stuff for any of these hosts...

     Without this flag you would have to write the condition/rule pair three times.
   - '`novary|NV`' (no vary)
     If a HTTP header is used in the condition, this flag prevents this header from being added to the Vary header of the response.
     Using this flag might break proper caching of the response if the representation of this response varies on the value of this header. So this flag should be only used if the meaning of the Vary header is well understood.

Example:

To rewrite the Homepage of a site according to the ```User-Agent:`'' header of the request, you can use the following:

    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]

Explanation: If you use a browser which identifies itself as 'Mozilla' (including Netscape Navigator, Mozilla etc), then you get the max homepage (which could include frames, or other special features). If you use the Lynx browser (which is terminal-based), then you get the min homepage (which could be a version designed for easy, text-only browsing). If neither of these conditions apply (you use any other browser, or your browser identifies itself as something non-standard), you get the std (standard) homepage.

RewriteRule
Defines rules for the rewriting engine
RewriteRule Pattern Substitution [flags]
server config
virtual host
directory
.htaccess
FileInfo

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 (%-decoded) URL-path of the request; subsequent patterns are applied to the output of the last matched RewriteRule.

# What is matched?

In VirtualHost context, The Pattern will initially be matched against the part of the URL after the hostname and port, and before the query string (e.g. "/app1/index.html").

In Directory and htaccess context, the Pattern will initially be matched against the filesystem path, after removing the prefix that lead the server to the current RewriteRule (e.g. "app1/index.html" or "index.html" depending on where the directives are defined).

If you wish to match against the hostname, port, or query string, use a RewriteCond with the `%{HTTP_HOST}`, `%{SERVER_PORT}`, or `%{QUERY_STRING}` variables respectively.

# Per-directory Rewrites

- The rewrite engine may be used in .htaccess files and in Directory sections, with some additional complexity.
- To enable the rewrite engine in this context, you need to set "`RewriteEngine On`" and "`Options FollowSymLinks`" must be enabled. If your administrator has disabled override of `FollowSymLinks` for a user's directory, then you cannot use the rewrite engine. This restriction is required for security reasons.
- When using the rewrite engine in `.htaccess` files the per-directory prefix (which always is the same for a specific directory) is automatically removed for the RewriteRule pattern matching and automatically added after any relative (not starting with a slash or protocol name) substitution encounters the end of a rule set. See the RewriteBase directive for more information regarding what prefix will be added back to relative substitions.
- If you wish to match against the full URL-path in a per-directory (htaccess) RewriteRule, use the `%{REQUEST_URI}` variable in a RewriteCond.
- The removed prefix always ends with a slash, meaning the matching occurs against a string which never has a leading slash. Therefore, a Pattern with `^/` never matches in per-directory context.
- Although rewrite rules are syntactically permitted in Location and Files sections, this should never be necessary and is unsupported.

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.

# Note

When using the NOT character to negate a pattern, you cannot include grouped wildcard parts in that pattern. This is because, when the pattern does NOT match (ie, the negation matches), there are no contents for the groups. Thus, if negated patterns are used, you cannot use `$N` in the substitution string!

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. Substitutions are only treated as a file-system path when the rule is configured in server (virtualhost) context and the first component of the path in the substitution is exists in the file-system
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.

Rewrite rules are applied to the results of previous rewrite rules, in the order in which they are defined in the config file. The URI or file path (see "What is matched?", above) is completely replaced by the Substitution and the rewriting process continues until all rules have been applied, or it is explicitly terminated by an `L` flag, or other flag which implies immediate termination, such as `END` or `F`.

# Modifying the Query String

By default, the query string is passed through unchanged. You can, however, create URLs in the substitution string containing a query string part. Simply use a question mark inside the substitution string to indicate that the following text should be re-injected into the query string. When you want to erase an existing query string, end the substitution string with just a question mark. To combine new and old query strings, use the `[QSA]` 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 flags in the following table. More details, and examples, for each flag, are available in the Rewrite Flags document.

Flag and syntax | Function
--- | ---
B | Escape non-alphanumeric characters before applying the transformation. details ...
chain|C | Rule is chained to the following rule. If the rule fails, the rule(s) chained to it will be skipped. details ...
cookie|CO=NAME:VAL | Sets a cookie in the client browser. Full syntax is: CO=NAME:VAL:domain[:lifetime[:path[:secure[:httponly]]]] details ...
discardpath|DPI | Causes the PATH_INFO portion of the rewritten URI to be discarded. details ...
env|E=[!]VAR[:VAL] | Causes an environment variable VAR to be set (to the value VAL if provided). The form !VAR causes the environment variable VAR to be unset.details ...
forbidden|F | Returns a 403 FORBIDDEN response to the client browser. details ...
gone|G | Returns a 410 GONE response to the client browser. details ...
Handler|H=Content-handler | Causes the resulting URI to be sent to the specified Content-handler for processing. details ...
last|L | Stop the rewriting process immediately and don't apply any more rules. Especially note caveats for per-directory and .htaccess context (see also the END flag). details ...
next|N | Re-run the rewriting process, starting again with the first rule, using the result of the ruleset so far as a starting point. details ...
nocase|NC | Makes the pattern comparison case-insensitive. details ...
noescape|NE | Prevent mod_rewrite from applying hexcode escaping of special characters in the result of the rewrite. details ...
nosubreq|NS | Causes a rule to be skipped if the current request is an internal sub-request. details ...
proxy|P | Force the substitution URL to be internally sent as a proxy request. details ...
passthrough|PT | Forces the resulting URI to be passed back to the URL mapping engine for processing of other URI-to-filename translators, such as `Alias` or `Redirect`. details ...
qsappend|QSA | Appends any query string created in the rewrite target to any query string that was in the original request URL. details ...
qsdiscard|QSD | Discard any query string attached to the incoming URI. details ...
redirect|R[=code] | Forces an external redirect, optionally with the specified HTTP status code. details ...
END | Stop the rewriting process immediately and don't apply any more rules. Also prevents further execution of rewrite rules in per-directory and .htaccess context. (Available in 2.3.9 and later) details ...
skip|S=num | Tells the rewriting engine to skip the next num rules if the current rule matches. details ...
type|T=MIME-type | Force the MIME-type of the target file to be the specified type. details ...

# Home directory expansion

When the substitution string begins with a string resembling "/~user" (via explicit text or backreferences), mod_rewrite performs home directory expansion independent of the presence or configuration of mod_userdir.

This expansion does not occur when the PT flag is used on the RewriteRule directive.

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