What this tool does
This is a searchable reference of every registered HTTP response status code (1xx–5xx): its name, what it means, and where it typically shows up in practice. It is a static, client-side reference — typing here does not send any request, it just filters the list below.
How to use it
- Search by code number (
404), name (not found) or a keyword such asredirectorrate limit. - Or filter by class using the 1xx–5xx tabs: 1xx is informational, 2xx is success, 3xx is redirection, 4xx is a client-side error, 5xx is a server-side error.
- Press
/anywhere on the page to jump to the search box.
As a rule of thumb: a 4xx means the request itself was the problem (bad input, missing auth, wrong method); a 5xx means the server failed a request it should have handled. That distinction is usually the fastest way to decide whether to fix the client or check the server logs first.
Frequently asked questions
What is the difference between a 301 and a 302 redirect?
301 Moved Permanently tells clients and search engines the resource has a new URL for good: browsers may cache the redirect, and crawlers transfer ranking signals to the new URL. 302 Found means the move is temporary, so the old URL should stay indexed and should not be cached long-term. Using 301 for a temporary maintenance redirect can get the wrong URL indexed; using 302 for a permanent move can leave the old URL competing with the new one in search results.
What is the difference between 401 and 403?
401 Unauthorized means the request lacks valid authentication; the server should also send a WWW-Authenticate header describing how to authenticate. 403 Forbidden means the server understood who you are but you are not allowed to access the resource regardless. In short: 401 is “log in”, 403 is “you are logged in, but no”.
What does a 429 status code mean and how should I respond to it?
429 Too Many Requests means the client hit a rate limit. The response should include a Retry-After header; well-behaved clients and scripts should back off and retry after that delay instead of hammering the endpoint, which can extend a temporary block.
What does a 503 mean, and how is it different from 500 and 502?
500 Internal Server Error is a generic failure in application code. 502 Bad Gateway means a proxy or load balancer got an invalid response from the upstream server. 503 Service Unavailable means the server is deliberately not serving requests right now, usually maintenance or overload, and is often paired with a Retry-After header. 504 Gateway Timeout is the 502 case where upstream never responded in time.
Why does 418 exist, and is it ever used seriously?
418 I'm a teapot comes from RFC 2324, an April Fools’ spec for a hypothetical coffee-pot protocol. It has no real semantics, but some frameworks keep it as an easter egg, and a few bot-mitigation tools reuse it as a deliberately odd status for blocked automated traffic.