HTTP status code reference · Guide
Common HTTP Error Codes
A short list of error codes accounts for most real-world failures. Here is what each is telling you.
Client errors (4xx)
400 means malformed input, 401 missing or invalid auth, 403 authenticated but not allowed, 404 not found, 422 well-formed but semantically invalid, and 429 too many requests. Fix the request side.
Server errors (5xx)
500 is a generic server failure, 502 a bad response from an upstream, and 503 a server temporarily unavailable. These point at the server or its dependencies, not your request.
Frequently asked questions
Can I use this for production work?
Yes, for inspection, formatting and quick generation. Still review the output before committing it to production code or configuration.
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