 Hypertext Transfer Protocol

The Hypertext Transfer Protocol is an application-level communication protocol for exchanging requests and responses about resources. In the client-server model, an HTTP request supplies an HTTP request method and target; an HTTP response supplies an HTTP status code and associated information. HTTP header fields convey metadata, and messages can carry content. These semantics are distinct from the particular wire format used by a protocol version.^[ref]

For a concrete exchange, a client can send method GET for https://example.org/manual. A successful response can carry status 200 and an HTML representation of the resource. A response with status 404 instead says that the server did not find a current representation, or is unwilling to disclose one; successful communication does not require successful retrieval.^[ref]

The request's URL identifies the target, while the response describes the outcome of this exchange. A later exchange can return different content or a different status. The protocol's stateless request semantics also do not prevent an application from maintaining state: the distinction concerns what a request must mean, not whether a user can have an ongoing session.^[ref]