About this tool
HTTP status codes are the three-digit answer of every web request: 2xx means it worked, 3xx that the client must go elsewhere, 4xx that the request has a problem and 5xx that the server failed. This reference lists the codes of RFC 9110 and the common extensions (429 Too Many Requests, 103 Early Hints, 451…), each with its official reason phrase, a plain explanation, when an API or website should return it and a link to the specification. Search by number (4 shows every 4xx) or by word (timeout, redirect, cache), or filter by class or by the most used. It answers the classic doubts: 401 or 403, 301 or 308, 400 or 422, 502 or 504.
How to use it
- 1 Type a code or a word, such as 404, 50 or timeout.
- 2 Or filter by class (1xx to 5xx) or by the most used codes.
- 3 Read what the code means and when to use it.
- 4 Open the RFC link for the exact definition.
Frequently asked questions
What is the difference between 401 and 403?
401 Unauthorized means the request has no valid credentials: the client should log in or refresh the token. 403 Forbidden means the server knows who you are and still refuses: logging in again will not help.
Should I use 301 or 308 for a permanent redirect?
For web pages, 301 is the usual choice and is understood by every browser and search engine. 308 means the same but guarantees the method and body are repeated, so use it for API endpoints that receive POST or PUT.
When should an API return 400 and when 422?
Use 400 when the request cannot be read at all — broken JSON, a missing parameter or wrong types. Use 422 when it is well-formed but the data fails your rules, such as an invalid e-mail or a date in the past.
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