This module provides for the customization of HTTP request and response headers.
Status: Extension
Source File: mod_headers.c
Module Identifier: headers_module
Compatibility: Available in Apache 1.2 and later.
RequestHeader appeared in Apache 2.0.
The directives provided by mod_header 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:
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*
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.
SetEnvIf MyRequestHeader value HAVE_MyRequestHeaderIf the header "MyRequestHeader: value" is present on the HTTP request, the response will contain the following header:
Header add MyHeader "%D %t mytext" env=HAVE_MyRequestHeader
MyHeader: D=3775428 t=991424704447256 mytext
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:
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 this 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.
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 action it performs is determined by the first argument. This can be one of the following values:
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 preceeded 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 preceeded by "D=".
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.