🔢 HTTP Status Code Reference

This tool groups its included HTTP status codes by class. Each entry shows its IANA registry name, a one-line description, and its RFC reference. Unused or obsoleted entries are marked separately.

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1. The five HTTP status code classes

HTTP status codes are grouped into five classes by their first digit: 1xx (informational, the request is still being processed), 2xx (success, the request was received, understood and accepted), 3xx (redirection, further action is needed to complete the request), 4xx (client error, something is wrong with the request itself), and 5xx (server error, the server failed to fulfill an apparently valid request). This design lets clients and proxies make a reasonable fallback decision from the first digit alone even for a status code they don't specifically recognize.

2. Commonly confused code pairs

401 Unauthorized actually means "not authenticated" (despite the name, it's an authentication problem, not authorization), while 403 Forbidden means the server refuses regardless of authentication because the client lacks permission. The distinction between 301/308 (permanent) and 302/307 (temporary) matters for caching and SEO; 307 and 308 specifically preserve the original HTTP method and body on redirect, unlike 302 and 301. 404 Not Found and 410 Gone are also often confused — 410 is a stronger signal meaning the resource existed before but was deliberately and permanently removed, telling clients to stop retrying.

3. RFC 9110 and status code standardization

RFC 9110 (HTTP Semantics), published in 2022, consolidated HTTP status code definitions that were previously scattered across RFC 7231 and related documents. This reference cites RFC 9110 section numbers (§15.x) as the primary source, while codes defined by separate specifications — such as WebDAV (RFC 4918) or the rate-limiting codes in RFC 6585 (429/431) — cite those RFCs instead. Using status codes precisely lets API clients, monitoring tools, and cache servers behave predictably.

Frequently asked questions

Is any standard status code missing from this list?

This table shows the entries included in this tool from the IANA HTTP Status Code Registry checked on September 9, 2026. Temporary registrations are excluded, and unused or obsoleted entries are marked separately. Later registry changes might not appear immediately.

How does the search work?

Any row whose code number, registry name, description, or historical search alias contains your text (case-insensitive) is shown. For example, searching "404", "not found", or "teapot" works.

What is the difference between 422 and 400?

400 means the request itself is malformed (bad syntax), while 422 means the syntax is fine but the instructions within it cannot be processed (e.g. a validation error).

Is this data sent anywhere?

No. This is entirely static reference data, and the search runs purely in your browser's JavaScript — nothing is sent to a server.