Status Code Categories
1xx — Informational
The request was received and the process is continuing. Rarely seen in normal API responses.
100 Continue101 Switching Protocols
2xx — Success
The request was successfully received, understood and accepted.
200 OK201 Created204 No Content206 Partial Content
3xx — Redirection
Further action is needed to complete the request. The client must follow the redirect.
301 Moved Permanently302 Found304 Not Modified307 Temporary Redirect
4xx — Client Errors
The request contains an error on the client's side — wrong URL, missing auth, bad data.
400 Bad Request401 Unauthorized403 Forbidden404 Not Found429 Too Many Requests
5xx — Server Errors
The server failed to fulfil a valid request. The problem is on the server's side.
500 Internal Server Error502 Bad Gateway503 Service Unavailable
Key Codes to Know
200 OK — Request succeeded. 201 Created — Resource was created (return after POST). 204 No Content — Success but no body (DELETE responses). 301 — Permanent redirect (SEO-safe, cached by browsers). 302 — Temporary redirect. 400 — Bad request syntax or invalid parameters. 401 — Authentication required. 403 — Authenticated but not authorised. 404 — Resource not found. 422 — Unprocessable entity (validation errors in API requests). 429 — Rate limit exceeded. 500 — Server error. 502 — Bad gateway (upstream server error). 503 — Service unavailable (overload or maintenance).
Frequently Asked Questions
What's the difference between 401 and 403?
401 Unauthorized means the client needs to authenticate first (login). 403 Forbidden means the client is authenticated but doesn't have permission.
When should an API return 201 vs 200?
Use 201 Created when a POST request creates a new resource. Use 200 OK for successful GET, PUT or PATCH responses.
What's the difference between 301 and 302?
301 is a permanent redirect — browsers and search engines cache the new URL. 302 is temporary — the original URL should be used in future. For SEO, 301 passes link equity; 302 does not.
Is 418 I'm a Teapot real?
Yes! Defined in RFC 2324 as an April Fools' joke in 1998. It's in the IANA registry and some servers implement it as an Easter egg.
Look up any status code
Open the HTTP Status Code Reference and find any code instantly — searchable, free.
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