HTTP Status Code Lookup

A 502 shows up in a log, a 418 in an API response, a 307 in a redirect chain, and all you want is to know what the number means before getting on with debugging. Type the code and get its official name instantly: 404 is Not Found, 429 is Too Many Requests, 503 is Service Unavailable. The table covers the most used codes across classes 1xx to 5xx, including the ones that tend to show up in proxy and API logs.

The first digit tells half the story: 1xx is informational, 2xx success, 3xx redirection, 4xx a client-side error and 5xx a server-side one. The traps live in the look-alike pairs: 401 means no valid credentials while 403 means authenticated but not allowed; 502 is a gateway getting an invalid response from the backend, while 504 is the backend not answering in time; and 308 is the version of 301 that preserves the POST method across the redirect.

What you get back is the official reason phrase, enough to point the investigation in the right direction; the full semantics (required headers, caching behavior) live in RFC 9110 and on MDN. Codes outside the list show as unknown, which includes non-standard ones like the 499 Nginx logs when a client gives up before the response arrives. The lookup runs against a local table right in your browser, with no external call.