HTTPRequest

An HTTP request is a message sent by a client to an origin server as part of the Hypertext Transfer Protocol. It is used to retrieve resources, submit data, or instruct a server to perform an action. Requests are typically initiated by web browsers, apps, or command-line tools and travel over TCP, with TLS providing encryption for HTTPS.

In raw form, an HTTP request consists of a request line, a set of headers, an empty line, and an optional body. The request line includes the method, the request target (the path or full URL), and the HTTP version. The request target may be origin-form, absolute-form, or asterisk-form depending on the method.

Headers convey metadata such as Host, User-Agent, Accept, and Content-Type. The Host header is mandatory in HTTP/1.1. If a body is present, its length is indicated by Content-Length and its format by Content-Type; compression can be negotiated via Accept-Encoding.

Common methods include GET, POST, PUT, PATCH, DELETE, HEAD, OPTIONS, TRACE, and CONNECT. GET and HEAD are typically safe and idempotent; POST, PUT, PATCH, and DELETE may change server state. Requests may carry cookies or authentication data in headers or bodies.

Servers respond with status codes indicating success or failure, and may also include headers and a response body. HTTP/2 and HTTP/3 introduce performance improvements such as multiplexing and reduced latency. Developers issue HTTP requests with tools like browsers, curl, or fetch-based APIs.