A response header is an HTTP header that can be used in an HTTP response and that doesn't relate to the content of the message. Response headers, like
Server 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
Content-Type header is a representation header indicating the original type of data in the body of the response message (prior to the encoding in the
Content-Encoding 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
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: mykey=myvalue; 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