Apache HTTP Server Version 2.0
Description: | Customization of HTTP request and response headers |
---|---|
Status: | Extension |
Module Identifier: | headers_module |
Source File: | mod_headers.c |
Compatibility: | RequestHeader is available only in Apache 2.0 |
This module provides directives to control and modify HTTP request and response headers. Headers can be merged, replaced or removed.
The directives provided by mod_headers
can occur almost anywhere within the server configuration. They are valid in the main server config and virtual host sections, inside <Directory>
, <Location>
and <Files>
sections, and within .htaccess
files.
The directives are processed in the following order:
<Directory>
sections and .htaccess
<Files>
<Location>
Order is important. These two headers have a different effect if reversed:
RequestHeader append MirrorID "mirror 12"
RequestHeader unset MirrorID
This way round, the MirrorID
header is not set. If reversed, the MirrorID header is set to "mirror 12".
Header echo ^TS
MyHeader
, to the response including a timestamp for when the request was received and how long it took to begin serving the request. This header can be used by the client to intuit load on the server or in isolating bottlenecks between the client and the server.
Header add MyHeader "%D %t"
results in this header being added to the response:
MyHeader: D=3775428 t=991424704447256
Header add MyHeader "Hello Joe. It took %D microseconds \
for Apache to serve this request."
results in this header being added to the response:
MyHeader: Hello Joe. It took D=3775428 microseconds for Apache to serve this request.
MyHeader
on the response if and only if header "MyRequestHeader" is present on the request. This is useful for constructing headers in response to some client stimulus. Note that this example requires the services of the mod_setenvif
module.
SetEnvIf MyRequestHeader value HAVE_MyRequestHeader
Header add MyHeader "%D %t mytext" env=HAVE_MyRequestHeader
If the header MyRequestHeader: value
is present on the HTTP request, the response will contain the following header:
MyHeader: D=3775428 t=991424704447256 mytext
Description: | Configure HTTP response headers |
---|---|
Syntax: | Header [condition] set|append|add|unset|echo header [value] [env=[!]variable] |
Context: | server config, virtual host, directory, .htaccess |
Override: | FileInfo |
Status: | Extension |
Module: | mod_headers |
Compatibility: | Condition is available in version 2.0.51 and later |
This directive can replace, merge or remove HTTP response headers. The header is modified just after the content handler and output filters are run, allowing outgoing headers to be modified.
The optional condition can be either onsuccess
or always
. It determines, which internal header table should be operated on. onsuccess
stands for 2xx
status codes and always
for all status codes (including 2xx
). Especially if you want to unset headers set by certain modules, you should try out, which table is affected.
The action it performs is determined by the second argument. This can be one of the following values:
set
append
add
unset
echo
This argument is followed by a header name, which can include the final colon, but it is not required. Case is ignored for set
, append
, add
and unset
. The header name for echo
is case sensitive and may be a regular expression.
For add
, append
and set
a value is specified as the third argument. If value contains spaces, it should be surrounded by doublequotes. value may be a character string, a string containing format specifiers or a combination of both. The following format specifiers are supported in value:
%t |
The time the request was received in Universal Coordinated Time since the epoch (Jan. 1, 1970) measured in microseconds. The value is preceded by t= . |
%D |
The time from when the request was received to the time the headers are sent on the wire. This is a measure of the duration of the request. The value is preceded by D= . |
%{FOOBAR}e |
The contents of the environment variable FOOBAR . |
When the Header
directive is used with the add
, append
, or set
argument, a fourth argument may be used to specify conditions under which the action will be taken. If the environment variable specified in the env=...
argument exists (or if the environment variable does not exist and env=!...
is specified) then the action specified by the Header
directive will take effect. Otherwise, the directive will have no effect on the request.
The Header
directives are processed just before the response is sent to the network. These means that it is possible to set and/or override most headers, except for those headers added by the header filter.
Description: | Configure HTTP request headers |
---|---|
Syntax: | RequestHeader set|append|add|unset header [value] |
Context: | server config, virtual host, directory, .htaccess |
Override: | FileInfo |
Status: | Extension |
Module: | mod_headers |
This directive can replace, merge or remove HTTP request headers. The header is modified just before the content handler is run, allowing incoming headers to be modified. The action it performs is determined by the first argument. This can be one of the following values:
set
append
add
append
should be used instead.unset
This argument is followed by a header name, which can include the final colon, but it is not required. Case is ignored. For add
, append
and set
a value is given as the third argument. If value contains spaces, it should be surrounded by double quotes. For unset, no value should be given.
The RequestHeader
directive is processed just before the request is run by its handler in the fixup phase. This should allow headers generated by the browser, or by Apache input filters to be overridden or modified.