Apache > HTTP Server > Documentation > Version 2.4 > Modules

Apache Module mod_substitute

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Description:Perform search and replace operations on response bodies
Module Identifier:substitute_module
Source File:mod_substitute.c
Compatibility:Available in Apache HTTP Server 2.2.7 and later


mod_substitute provides a mechanism to perform both regular expression and fixed string substitutions on response bodies.


Bugfix checklist

See also


Substitute Directive

Description:Pattern to filter the response content
Syntax:Substitute s/pattern/substitution/[infq]
Context:directory, .htaccess

The Substitute directive specifies a search and replace pattern to apply to the response body.

The meaning of the pattern can be modified by using any combination of these flags:

Perform a case-insensitive match.
By default the pattern is treated as a regular expression. Using the n flag forces the pattern to be treated as a fixed string.
The f flag causes mod_substitute to flatten the result of a substitution allowing for later substitutions to take place on the boundary of this one. This is the default.
The q flag causes mod_substitute to not flatten the buckets after each substitution. This can result in much faster response and a decrease in memory utilization, but should only be used if there is no possibility that the result of one substitution will ever match a pattern or regex of a subsequent one.


<Location "/">
    AddOutputFilterByType SUBSTITUTE text/html
    Substitute "s/foo/bar/ni"

If either the pattern or the substitution contain a slash character then an alternative delimiter should be used:

Example of using an alternate delimiter

<Location "/">
    AddOutputFilterByType SUBSTITUTE text/html
    Substitute "s|<BR */?>|<br />|i"

Backreferences can be used in the comparison and in the substitution, when regular expressions are used, as illustrated in the following example:

Example of using backreferences and captures

<Location "/">
    AddOutputFilterByType SUBSTITUTE text/html
    # "foo=k,bar=k" -> "foo/bar=k"
    Substitute "s|foo=(\w+),bar=\1|foo/bar=$1"

A common use scenario for mod_substitute is the situation in which a front-end server proxies requests to a back-end server which returns