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_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:
This way round, the MirrorID header is not set. If reversed, the MirrorID header is set to "mirror 12".
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
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 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 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
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.