HTTP

HTTP (HyperText Transfer Protocol) is the application-layer protocol of the Web, built on a request-response model, stateless, and the foundation of web communication.

Purpose

It provides the application-layer protocol for distributed hypermedia systems, with flexible content negotiation and caching.

Mechanism

The client sends a request (method GET/POST/PUT/DELETE + URL + headers + body) and the server returns a response (status code + headers + body). It is stateless (cookies carry sessions). HTTP/2 adds multiplexing, HTTP/3 builds on QUIC, and HTTP/1 is a text protocol.

Use cases

Web page and API communication
RESTful API
File download and upload
WebSocket upgrades

Examples

Input

GET /api/users HTTP/1.1

Output

200 OK + JSON body

Request-response

Common errors

Using GET for operations with side effects: Use POST/PUT/DELETE for state-changing operations

Related terms

HTTPS is HTTP over TLS: it encrypts HTTP communication at the transport layer, providing confidentiality, integrity, and server authentication, and it is the modern web standard.

TLS (Transport Layer Security) provides encryption, integrity, and authentication at the transport layer; it replaced SSL and underpins HTTPS, SMTPS, and more.

A cookie is a key-value pair set by the server and stored by the browser, sent automatically with same-origin requests for session and state management.

CORS (Cross-Origin Resource Sharing) is a browser security mechanism that uses HTTP headers to control whether a page may access resources from a different origin, preventing cross-site reads.

Related tools

HTTP Status Codes

Reference table of common HTTP status codes (1xx-5xx) with names, categories, and descriptions. Free, private, and 100% client-side.

Parse a URL into its components: protocol, host, path, query, hash, port, username, and password. Free, private, and 100% client-side.

References