Complete reference of HTTP status codes defined in RFC 9110 (June 2022): codes from 100 to 599, grouped by category (1xx informational, 2xx success, 3xx redirection, 4xx client error, 5xx server error). For each code: name, semantics, typical use cases, anti-patterns (when NOT to use), cURL example. Filterable by category + searchable by name or code.
Type a number (e.g. 404, 502) or part of the name (e.g. 'redirect', 'unauthorized', 'gone'). Filter applies case-insensitive match on both code and name.
The 5 top chips filter by category: 1xx, 2xx, 3xx, 4xx, 5xx. Click 'All' to reset.
Each card shows: code + name (e.g. '301 Moved Permanently'), semantic description, two sections 'when to use' and 'when NOT to use' to avoid common anti-patterns, ready-to-copy cURL example.
The problem with names. 'Unauthorized' (401) means 'not authenticated', NOT 'not authorized'. 'Forbidden' (403) is instead 'not authorized'. The confusion is widespread even among senior devs. References that clearly explain RFC semantics reduce these errors in production. Similar example: 422 'Unprocessable Content' vs 400 'Bad Request' - when to use one vs the other? The reference here provides practical rules.
RFC 9110 (June 2022). The current specification unifies previous RFC 7230-7235 and introduces some new status codes (e.g. 421 Misdirected Request, 425 Too Early). The reference is aligned with RFC 9110 with updated anti-patterns for modern APIs (REST, GraphQL, gRPC-HTTP/2).
What the tool does NOT cover. WebDAV status codes (RFC 4918: 102, 207, 422, 423, 424, 507) are included only where they made it into RFC 9110. Cloudflare-custom codes (520-527), 'I'm a teapot' (418, RFC 2324 April Fool's joke) are treated as curiosities. For ad-hoc protocol tools consult the specific spec.
Maurizio Fonte, senior IT consultant with 20+ years in PHP, Laravel, unmanaged Linux infrastructure, applied cybersecurity and AI/LLM integration. Production backends, legacy code modernization, security audits, custom AI agents and MCP servers: the work behind every tool published here.
About Maurizio Fonte