A response header is an that can be used in an HTTP response and that doesn’t relate to the content of the message. Response headers, like , or are used to give a more detailed context of the response.

Not all headers appearing in a response are categorized as response headers by the specification. For example, the header is a indicating the original type of data in the body of the response message (prior to the encoding in the representation header being applied). However, “conversationally” all headers are usually referred to as response headers in a response message.

The following shows a few response and representation headers after a request.

200 OK
Access-Control-Allow-Origin: *
Connection: Keep-Alive
Content-Encoding: gzip
Content-Type: text/html; charset=utf-8
Date: Mon, 18 Jul 2016 16:06:00 GMT
ETag: "c561c68d0ba92bbeb8b0f612a9199f722e3a621a"
Keep-Alive: timeout=5, max=997
Last-Modified: Mon, 18 Jul 2016 02:36:04 GMT
Server: Apache
Set-Cookie: my-key=my value; expires=Mon, 17-Jul-2017 16:06:00 GMT; Max-Age=31449600; Path=/; secure
Transfer-Encoding: chunked
Vary: Cookie, Accept-Encoding
X-Backend-Server: developer2.webapp.scl3.mozilla.com
X-Cache-Info: not cacheable; meta data too large
X-kuma-revision: 1085259
x-frame-options: DENY

See also

• List of all HTTP headers

Related glossary terms: