mod_setenvif - Apache HTTP Server Version 2.5

mod_setenvif - Apache HTTP Server Version 2.5
Modules
Directives
FAQ
Glossary
Apache HTTP Server Version 2.5
Apache
HTTP Server
Documentation
Version 2.5
Modules
Apache Module mod_setenvif
Available Languages:
en
fr
ja
ko
tr
Description:
Allows the setting of environment variables based
on characteristics of the request
Status:
Base
Module Identifier:
setenvif_module
Source File:
mod_setenvif.c
Summary
The
mod_setenvif
module allows you to set
internal environment variables according to whether different aspects of
the request match regular expressions you specify. These
environment variables can be used by other parts of the server
to make decisions about actions to be taken, as well as becoming
available to CGI scripts and SSI pages.
The directives are considered in the order they appear in
the configuration files. So more complex sequences can be used,
such as this example, which sets
netscape
if the
browser is mozilla but not MSIE.
BrowserMatch ^Mozilla netscape
BrowserMatch MSIE !netscape
When the server looks up a path via an internal
subrequest
such as looking
for a
DirectoryIndex
or generating a directory listing with
mod_autoindex
per-request environment variables are
not
inherited in the
subrequest. Additionally,
SetEnvIf
directives
are not separately evaluated in the subrequest due to the API phases
mod_setenvif
takes action in.
A regular expression only needs quoting when it contains space,
in which case single and double quotes are equivalent. Unlike
mod_rewrite
mod_setenvif
strips every
other backslash when parsing the expression; thus
\\
requires
\\\
, and
\\\
requires
\\\\\
Directives
BrowserMatch
BrowserMatchNoCase
SetEnvIf
SetEnvIfExpr
SetEnvIfNoCase
Bugfix checklist
httpd changelog
Known issues
Report a bug
See also
Environment Variables in Apache HTTP Server
Comments
BrowserMatch
Directive
Description:
Sets environment variables conditional on HTTP User-Agent
Syntax:
BrowserMatch
regex [!]env-variable
[=
value
[[!]
env-variable
[=
value
]] ...
Context:
server config, virtual host, directory, .htaccess
Override:
FileInfo
Status:
Base
Module:
mod_setenvif
The
BrowserMatch
is a special cases of the
SetEnvIf
directive that
sets environment variables conditional on the
User-Agent
HTTP request header. The following two
lines have the same effect:
BrowserMatch Robot is_a_robot
SetEnvIf User-Agent Robot is_a_robot
Some additional examples:
BrowserMatch ^Mozilla forms jpeg=yes browser=netscape
BrowserMatch "^Mozilla/[2-3]" tables agif frames javascript
BrowserMatch MSIE !javascript
BrowserMatchNoCase
Directive
Description:
Sets environment variables conditional on User-Agent without
respect to case
Syntax:
BrowserMatchNoCase
regex [!]env-variable
[=
value
[[!]
env-variable
[=
value
]] ...
Context:
server config, virtual host, directory, .htaccess
Override:
FileInfo
Status:
Base
Module:
mod_setenvif
The
BrowserMatchNoCase
directive is
semantically identical to the
BrowserMatch
directive.
However, it provides for case-insensitive matching. For
example:
BrowserMatchNoCase mac platform=macintosh
BrowserMatchNoCase win platform=windows
The
BrowserMatch
and
BrowserMatchNoCase
directives are special cases of
the
SetEnvIf
and
SetEnvIfNoCase
directives. The following two lines have the same effect:
BrowserMatchNoCase Robot is_a_robot
SetEnvIfNoCase User-Agent Robot is_a_robot
SetEnvIf
Directive
Description:
Sets environment variables based on attributes of the request
Syntax:
SetEnvIf
attribute
regex [!]env-variable
[=
value
[[!]
env-variable
[=
value
]] ...
Context:
server config, virtual host, directory, .htaccess
Override:
FileInfo
Status:
Base
Module:
mod_setenvif
The
SetEnvIf
directive defines
environment variables based on attributes of the request. The
attribute
specified in the first argument can be one of the
following things:
An HTTP request header field (see
RFC2616
for more information about these); for example:
Host
User-Agent
Referer
, and
Accept-Language
. A regular expression may be
used to specify a set of request headers.
One of the following aspects of the request:
Remote_Host
- the hostname (if available) of
the client making the request
Remote_Addr
- the IP address of the client
making the request
Server_Addr
- the IP address of the server
on which the request was received (only with versions later
than 2.0.43)
Request_Method
- the name of the method
being used (
GET
POST
et
cetera
Request_Protocol
- the name and version of
the protocol with which the request was made (
e.g.
"HTTP/0.9", "HTTP/1.1",
etc.
Request_URI
- the resource requested on the HTTP
request line -- generally the portion of the URL
following the scheme and host portion without the query string. See
the
RewriteCond
directive of
mod_rewrite
for extra information on
how to match your query string.
The name of an environment variable in the list of those
associated with the request. This allows
SetEnvIf
directives to test against the result
of prior matches. Only those environment variables defined by earlier
SetEnvIf[NoCase]
directives are available for testing in
this manner. 'Earlier' means that they were defined at a broader scope
(such as server-wide) or previously in the current directive's scope.
Environment variables will be considered only if there was no match
among request characteristics and a regular expression was not
used for the
attribute
The second argument (
regex
) is a
regular expression
. If the
regex
matches against the
attribute
, then the remainder of the
arguments are evaluated.
The rest of the arguments give the names of variables to set, and
optionally values to which they should be set. These take the form
of
varname
, or
varname
, or
varname
value
In the first form, the value will be set to "1". The second
will remove the given variable if already defined, and the
third will set the variable to the literal value given by
value
. Since version 2.0.51, Apache httpd will
recognize occurrences of
$1
..
$9
within
value
and replace them by parenthesized subexpressions
of
regex
$0
provides access to the whole
string matched by that pattern.
If the special value
--early
is specified, and this
directive is not in directory context, the directive will be evaluated
earlier during request processing. This allows the output variables
set by this directive to be used as input to the "early mode" option of
the
RequestHeader
directive.
Available in 2.5.1 and later.
SetEnvIf Request_URI "\.gif$" object_is_image=gif
SetEnvIf Request_URI "\.jpg$" object_is_image=jpg
SetEnvIf Request_URI "\.xbm$" object_is_image=xbm

SetEnvIf Referer www\.mydomain\.example\.com intra_site_referral

SetEnvIf object_is_image xbm XBIT_PROCESSING=1

SetEnvIf Request_URI "\.(.*)$" EXTENSION=$1

SetEnvIf ^TS ^[a-z] HAVE_TS
The first three will set the environment variable
object_is_image
if the request was for an image
file, and the fourth sets
intra_site_referral
if
the referring page was somewhere on the
www.mydomain.example.com
Web site.
The last example will set environment variable
HAVE_TS
if the request contains any headers that
begin with "TS" whose values begins with any character in the
set [a-z].
See also
Environment Variables in Apache HTTP Server
for additional examples.
SetEnvIfExpr
Directive
Description:
Sets environment variables based on an ap_expr expression
Syntax:
SetEnvIfExpr
expr
[!]env-variable
[=
value
[[!]
env-variable
[=
value
]] ...
Context:
server config, virtual host, directory, .htaccess
Override:
FileInfo
Status:
Base
Module:
mod_setenvif
The
SetEnvIfExpr
directive defines
environment variables based on an
expression
These expressions will be evaluated at runtime,
and applied
env-variable
in the same fashion as
SetEnvIf
, including backreferences.
SetEnvIfExpr "tolower(req('X-Sendfile')) == 'd:\images\very_big.iso')" iso_delivered
SetEnvIfExpr "tolower(req('X-Sendfile')) =~ /(.*\.iso$)/" iso-path=$1
This would set the environment variable
iso_delivered
every time our application attempts to send it via
X-Sendfile
A more useful example would be to set the variable rfc1918 if the
remote IP address is a private address according to RFC 1918:
SetEnvIfExpr "-R '10.0.0.0/8' || -R '172.16.0.0/12' || -R '192.168.0.0/16'" rfc1918
See also
Expressions in Apache HTTP Server
for a complete reference and more examples.

can be used to achieve similar
results.
mod_filter
SetEnvIfNoCase
Directive
Description:
Sets environment variables based on attributes of the request
without respect to case
Syntax:
SetEnvIfNoCase
attribute regex
[!]env-variable
[=
value
[[!]
env-variable
[=
value
]] ...
Context:
server config, virtual host, directory, .htaccess
Override:
FileInfo
Status:
Base
Module:
mod_setenvif
The
SetEnvIfNoCase
is semantically identical to
the
SetEnvIf
directive,
and differs only in that the regular expression matching is
performed in a case-insensitive manner. For example:
SetEnvIfNoCase Host Example\.Org site=example
This will cause the
site
environment variable
to be set to "
example
" if the HTTP request header
field
Host:
was included and contained
Example.Org
example.org
, or any other
combination.
Available Languages:
en
fr
ja
ko
tr
Copyright 2026 The Apache Software Foundation.
Licensed under the
Apache License, Version 2.0
Modules
Directives
FAQ
Glossary