An extensible and open representation for data types (MIME Types)

HTTP uses Internet Media Types (formerly referred to as MIME Content-Types) to provide open and extensible data typing and type negotiation. For mail applications, where there is no type negotiation between sender and receiver, it's reasonable to put strict limits on the set of allowed media types. With HTTP, where the sender and recipient can communicate directly, applications are allowed more freedom in the use of non-registered types. When the client sends a transaction to the server, headers are attached that conform to standard Internet e-mail specifications (RFC 822). Most client requests expect an answer either in plain text or HTML. When the HTTP Server transmits information back to the client, it includes a MIME-like (Multipart Internet Mail Extension) header to inform the client what kind of data follows the header. Translation then depends on the client possessing the appropriate utility (image viewer, movie player, etc.) corresponding to that data type.