Day Software HP Microsoft Adobe Systems Microsoft W3C/MIT The Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypermedia information systems. HTTP has been in use by the World Wide Web global information initiative since 1990. This document is Part 2 of the eight-part specification that defines the protocol referred to as "HTTP/1.1" and, taken together, updates RFC 2616 and RFC 2617. Part 2 defines the semantics of HTTP messages as expressed by request methods, request-header fields, response status codes, and response- header fields.