HTTPprotocol

HTTP (Hypertext Transfer Protocol) is an application layer protocol used for transferring data on the World Wide Web. It enables clients and servers to exchange requests and responses and typically runs over TCP. When protected by TLS, HTTP operates as HTTPS. The protocol is defined by RFCs issued by the IETF and has evolved since its origins in the early 1990s as part of Tim Berners-Lee’s web architecture.

HTTP follows a request–response model. A client sends a request with a method, a target URI, and an HTTP version, followed by headers and an optional body. The server replies with a status line, headers, and an optional body. HTTP is stateless by default; state is usually maintained with cookies or tokens.

Common methods include GET, POST, PUT, PATCH, DELETE, HEAD, OPTIONS, and TRACE. Status codes are grouped into classes, such as 2xx (success), 3xx (redirection), 4xx (client errors), and 5xx (server errors). Headers convey metadata like content type, length, caching directives, and authentication. Features include content negotiation and caching with Cache-Control, ETag, If-Modified-Since, and Expires.

Versions and evolution: HTTP/1.0 introduced simple connections; HTTP/1.1 added persistent connections and Host headers. HTTP/2 uses binary framing, multiplexing, header compression, and server push. HTTP/3, built on QUIC, aims to reduce latency. Security practices emphasize HTTPS, HSTS, and proper certificate validation. Typical ports are 80 for HTTP and 443 for HTTPS.