HTTP Status Codes

Look up HTTP status codes by category or keyword, with meanings, typical scenarios, and debugging hints.

What this tool does

Covers 37 RFC-standard HTTP status codes, each with a plain-language explanation and typical scenarios. Browse by category (1xx informational, 2xx success, 3xx redirection, 4xx client errors, 5xx server errors) or search by number or keyword (searching “cache” finds 304). More than definitions — each entry notes where to look when debugging.

Typical use cases

Pinpointing responsibility when an API errors: 4xx means the requester's problem (parameters, auth, rate), 5xx means the server's (crashes, dead upstreams); choosing semantically correct codes when designing REST APIs (201 for creation, 429 for throttling); telling 502 (invalid upstream response) from 504 (upstream timeout) when debugging a gateway.

Caveats

Common confusions: 401 is “not authenticated” (log in), 403 is “authenticated but forbidden”; 301 is permanent and transfers search ranking, 302 is temporary; 404 says “not here, or not saying”, 410 says “was here, now deleted”. 307/308 are the strict versions of 302/301 — they never rewrite POST to GET. Frameworks and CDNs also use non-standard codes (Nginx 499, Cloudflare's 5xx series) that are not listed here.