HTTP status codes

One page per status code: what it means, the spec section that defines it, the causes that actually produce it in production, how to debug it, and working curl, Python, and Node examples. Codes are taken from theIANA HTTP Status Code Registry; widely-deployed vendor codes that are not registered are grouped separately and labelled as non-standard.

Looking for a searchable single-page cheat sheet instead? Use theHTTP status code reference tool.

1xx — Informational

Interim responses. The client should expect a final status after these, and most HTTP libraries swallow them without ever telling you they arrived.

2xx — Success

The request was received, understood, and accepted. Which 2xx you pick tells the client whether a body follows and whether anything was created.

3xx — Redirection

Further action is needed to complete the request. The difference between the redirect codes is whether the method is preserved and whether caches may keep the mapping.

4xx — Client error

The request was malformed, unauthorised, or asked for something that is not there. A 4xx means retrying the identical request will not help.

Non-standard 4xx codes

Not in the IANA registry. These are vendor-specific codes you will still meet in real logs.

5xx — Server error

The server knows it failed, or cannot do what was asked. Most 5xx codes are retryable, and the interesting question is usually which hop in the chain produced it.

Non-standard 5xx codes

Not in the IANA registry. These are vendor-specific codes you will still meet in real logs.