HTTP Status Codes are standardized three-digit numbers returned by a web server to indicate the result of a client’s request. Introduced with the HTTP/1.0 specification in 1996, they categorize responses into five classes: 1xx (informational), 2xx (success), 3xx (redirection), 4xx (client error), and 5xx (server error). For example, 200 OK signals a successful request, 404 Not Found indicates a missing resource, and 500 Internal Server Error reflects server-side failure. Status codes provide a machine-readable way to convey request outcomes, guide client behavior, and troubleshoot web applications. They are fundamental in HTTP communication, forming the backbone of error handling, redirection, and protocol compliance for web services and APIs.
400 Bad Request 401 Unauthorized 402 Payment Required 403 Forbidden 404 Not Found 405 Method Not Allowed 406 Not Acceptable 407 Proxy Authentication Required 408 Request Timeout 409 Conflict 410 Gone 411 Length Required 412 Precondition Failed 413 Payload Too Large 414 URI Too Long 415 Unsupported Media Type 416 Range Not Satisfiable 417 Expectation Failed 418 I'm a teapot 421 Misdirected Request 422 Unprocessable Entity (WebDAV) 423 Locked (WebDAV) 424 Failed Dependency (WebDAV) 425 Too Early 426 Upgrade Required 428 Precondition Required 429 Too Many Requests 431 Request Header Fields Too Large 451 Unavailable For Legal Reasons