Warning: The current HTTP/1.1 specification no longer refers to entities, entity headers or entity-body. Some of the fields are now referred to as Representation header fields.
An entity header is an HTTP header that describes the payload of an HTTP message (i.e. metadata about the message body). Entity headers include:
Expires, etc. Entity headers may be present in both HTTP request and response messages.
POST /myform.html HTTP/1.1 Host: developer.mozilla.org User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:50.0) Gecko/20100101 Firefox/50.0 Content-Length: 128