Reference

HTTP status codes

Every time a browser or a program asks a web server for something, the server replies with a three-digit status code that says what happened. The first digit sets the class, from 2xx for success to 4xx for a problem with the request and 5xx for a problem on the server. Here is the full list in plain English, with detail pages for the codes worth knowing well.

Reading this as a program? This page is available as markdown at /reference/http-status-codes/index.md, and each code has its own markdown twin.

1xx Informational

Informational: the request was received and the process is continuing.

100	Continue	The client should continue with its request.
101	Switching Protocols	The server is switching protocols as requested.
103	Early Hints	Preliminary headers sent while the response is prepared.

2xx Success

Success: the request was received, understood and accepted.

200	OK	The request succeeded. The most common status code.
201	Created	The request succeeded and a new resource was created.
202	Accepted	The request was accepted but not yet processed.
204	No Content	Success, but there is no body to return.
206	Partial Content	Part of the resource is returned, used for range requests.

3xx Redirection

Redirection: further action is needed to complete the request.

301	Moved Permanently	The resource has a new permanent URL.
302	Found	The resource is temporarily at a different URL.
304	Not Modified	The cached copy is still valid, so nothing is sent.
307	Temporary Redirect	Temporary redirect that keeps the request method.
308	Permanent Redirect	Permanent redirect that keeps the request method.

4xx Client error

Client error: the request has a problem the client must fix.

400	Bad Request	The server cannot understand the request.
401	Unauthorized	Authentication is required and has failed or is missing.
402	Payment Required	Reserved for payment. Newly relevant for paid APIs and AI agents.
403	Forbidden	The server understood the request but refuses to authorise it.
404	Not Found	The server cannot find the requested resource.
405	Method Not Allowed	The request method is not supported for this resource.
408	Request Timeout	The server timed out waiting for the request.
409	Conflict	The request conflicts with the current state of the resource.
410	Gone	The resource is permanently gone with no forwarding address.
418	I'm a Teapot	An April Fools joke from 1998 that became a real, beloved code.
422	Unprocessable Content	The request is well formed but semantically invalid.
429	Too Many Requests	The client has sent too many requests in a given time. Central to rate limiting.
451	Unavailable For Legal Reasons	The resource is blocked for legal reasons.

5xx Server error

Server error: the server failed to fulfil a valid request.

500	Internal Server Error	A generic error: something went wrong on the server.
501	Not Implemented	The server does not support the functionality required.
502	Bad Gateway	A server acting as a gateway got an invalid response upstream.
503	Service Unavailable	The server is temporarily unable to handle the request.
504	Gateway Timeout	A gateway server did not get a response in time.

Meanings follow the IETF HTTP specification (RFC 9110) and MDN. Last reviewed: 10 July 2026.