How http status code lookup works
Every HTTP response starts with a three-digit status code that tells the client how the request went. The first digit groups codes into five classes: 1xx informational, 2xx success, 3xx redirection, 4xx client error, and 5xx server error. This tool covers all of the IANA-registered codes you will actually meet — plus a few widely used non-standard ones like nginx's 499 — each with its official name and a plain-English explanation of when it appears.
You can work three ways. Enter a full three-digit code like 404 for a detailed answer: the name, the class with its range, and a description of the usual cause. Enter a single class digit like 4 to list every client-error code. Or type a keyword like "redirect", "timeout", or "teapot" and the tool ranks matching codes — exact name matches first, then name mentions, then descriptions.
Codes that are not part of the official IANA registry are flagged as non-standard, so you never mistake a server-specific convention like 499 (Client Closed Request) for something a browser or HTTP library is guaranteed to understand. A reference table of the five classes stays at the bottom of the page for quick orientation.