Name

Header

Synopsis

Header set|append|add header value

or:

Header unset headerServer config, virtual host, access.conf, .htaccess

This directive can replace, merge, or remove HTTP response headers. The action it performs is determined by the first argument. This can be one of the following values:

set

The response header is set, replacing any previous header with this name.

append

The response header is appended to any existing header of the same name. When a new value is merged onto an existing header, it is separated from the existing header with a comma. This is the HTTP standard way of giving a header multiple values.

add

The response header is added to the existing set of headers, even if this header already exists. This can result in two (or more) headers having the same name. This can lead to unforeseen consequences, and in general append should be used instead.

unset

The response header of this name is removed, if it exists. If there are multiple headers of the same name, all will be removed.

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.

Order of Processing

The Header directive can occur almost anywhere within the server configuration. It is valid in the main server config and virtual host sections, inside <Directory>, <Location>, and <Files> sections, and within .htaccess files.

The Header directives are processed in the following order:

main server 
virtual host 
<Directory> sections and .htaccess 
<Location> 
<Files>

Order is important. These two headers have a different effect if reversed:

Header append Author "John P. Doe"
Header unset Author

This way round, the Author header is not set. If reversed, the Author header is set to "John P. Doe".

The Header directives are processed just before the response is sent by its handler. These means that some headers that are added just before the response is sent cannot be unset or overridden. This includes headers such as "Date" and "Server".