HTTP (HyperText Transfer Protocol)

HTTP (HyperText Transfer Protocol) is the protocol browsers and servers use to exchange web pages and data. A client sends a request with a method such as GET or POST, a URL and headers; the server replies with a status code, headers and usually a body such as HTML or JSON.

HTTP is stateless: each request is independent, so cookies or tokens are used to remember users between requests. Status codes tell the result, for example 200 OK, 301 Moved Permanently, 404 Not Found and 500 Internal Server Error. Plain HTTP is not encrypted; HTTPS adds encryption.

GET /index.html HTTP/1.1
Host: example.com
Accept: text/html

HTTP/1.1 200 OK
Content-Type: text/html; charset=utf-8

<!DOCTYPE html>...