HTTP Status Codes — Complete Reference List

HTTP response code table

Code	Name	Meaning
1xx Informational
100	Continue	The server received the request headers and the client should send the request body.
101	Switching Protocols	The server agrees to switch to the protocol requested in the Upgrade header.
102	Processing	The server accepted the full request but has not completed it yet (WebDAV).
103	Early Hints	Preliminary headers, mostly Link preload hints, sent before the final response.
2xx Success
200	OK	The request succeeded and the response carries the requested representation.
201	Created	The request succeeded and a new resource was created, usually named in Location.
202	Accepted	The request was accepted for asynchronous processing that has not finished.
203	Non-Authoritative Information	The response was modified by a transforming proxy on the way.
204	No Content	The request succeeded and there is intentionally no response body.
205	Reset Content	The request succeeded and the client should reset the document view or form.
206	Partial Content	The response delivers only the byte range requested with the Range header.
3xx Redirection
300	Multiple Choices	Several representations exist and the client should pick one of them.
301	Moved Permanently	The resource has a permanent new URL and links should be updated.
302	Found	The resource temporarily lives at a different URL; keep using the original.
303	See Other	The result is available at another URL and should be fetched with GET.
304	Not Modified	The cached copy is still valid, so no body is sent again.
307	Temporary Redirect	Temporary redirect that must keep the original HTTP method and body.
308	Permanent Redirect	Permanent redirect that must keep the original HTTP method and body.
4xx Client Errors
400	Bad Request	The server cannot process the request because it is malformed.
401	Unauthorized	Valid authentication credentials are required and missing or wrong.
402	Payment Required	Reserved status, used in practice by some APIs for billing limits.
403	Forbidden	The server understood the request but refuses to authorize it.
404	Not Found	No resource exists at the requested URL.
405	Method Not Allowed	The URL exists but does not support this HTTP method.
406	Not Acceptable	No representation matches the Accept negotiation headers.
407	Proxy Authentication Required	The client must authenticate with the proxy first.
408	Request Timeout	The server closed the connection because the request took too long to arrive.
409	Conflict	The request conflicts with the current state of the resource, e.g. an edit collision.
410	Gone	The resource was deliberately removed and will not return.
411	Length Required	The request must include a Content-Length header.
412	Precondition Failed	A conditional header such as If-Match evaluated to false.
413	Content Too Large	The request body exceeds the size the server accepts.
414	URI Too Long	The request URL is longer than the server will parse.
415	Unsupported Media Type	The request body format is not supported for this resource.
416	Range Not Satisfiable	The requested byte range lies outside the resource size.
417	Expectation Failed	The Expect request header could not be fulfilled.
418	I'm a teapot	An April Fools status from RFC 2324; some APIs use it as an easter egg.
421	Misdirected Request	The request reached a server that cannot produce a response for this authority.
422	Unprocessable Content	The request is well-formed but semantically invalid, common in REST validation.
425	Too Early	The server refuses to process a request that might be replayed (TLS early data).
426	Upgrade Required	The client must switch to a different protocol as listed in Upgrade.
428	Precondition Required	The server requires a conditional request to prevent lost updates.
429	Too Many Requests	The client exceeded a rate limit; Retry-After hints when to try again.
431	Request Header Fields Too Large	Headers, often cookies, exceed the server's size limits.
451	Unavailable For Legal Reasons	Access is blocked for legal reasons such as court orders.
5xx Server Errors
500	Internal Server Error	The server hit an unexpected error while handling the request.
501	Not Implemented	The server does not recognize or support the request method.
502	Bad Gateway	A gateway or proxy received an invalid response from the upstream server.
503	Service Unavailable	The server is temporarily unable to serve, due to overload or maintenance.
504	Gateway Timeout	A gateway or proxy gave up waiting for the upstream server.
505	HTTP Version Not Supported	The server does not support the HTTP protocol version used.
506	Variant Also Negotiates	A content negotiation misconfiguration on the server.
507	Insufficient Storage	The server cannot store what it needs to complete the request (WebDAV).
508	Loop Detected	The server detected an infinite loop while processing (WebDAV).
510	Not Extended	The request needs further extensions that were not supplied.
511	Network Authentication Required	The network (e.g. a captive portal) requires authentication first.

1xx Informational

Informational responses confirm that the request was received and the client can continue. They are interim: a final status always follows. The one you will actually meet in the wild is 103 Early Hints, which lets servers push preload hints before the full response is ready.

2xx Success

Success responses mean the request was understood and accepted. 200 OK carries the result in the body, 201 Created announces a new resource, and 204 No Content confirms success with deliberately nothing to return.

3xx Redirection

Redirection responses point the client somewhere else. The key distinction is permanence — 301/308 are permanent, 302/307 temporary — and whether the HTTP method must be preserved (307/308) or may change to GET (301/302). 304 Not Modified is the special case that powers browser caching.

4xx Client Errors

Client errors mean the request itself was rejected. The everyday ones: 400 malformed request, 401 authentication required, 403 access refused, 404 nothing at this URL and 429 rate limit exceeded.

5xx Server Errors

Server errors mean the server failed on a request that may have been perfectly valid. 500 is an application crash, 502 and 504 are proxies reporting a broken or silent upstream, and 503 is deliberate, temporary unavailability.

How to read a status code

The first digit is the class: 1xx informational, 2xx success, 3xx redirection, 4xx client error, 5xx server error. A client that meets an unknown code can safely fall back to treating it as the x00 code of its class — that is how new codes stay backward-compatible. When debugging, always look at the response headers next to the code: Location explains redirects, Allow explains 405, Retry-After explains 429 and 503.

Examples

200 OK                    — page served normally
301 Moved Permanently     — URL changed for good, follow Location
304 Not Modified          — your cached copy is still valid
404 Not Found             — nothing exists at this URL
429 Too Many Requests     — rate limit hit, wait Retry-After seconds
503 Service Unavailable   — temporary downtime or maintenance

FAQ

What is HTTP 404?

HTTP 404 means the requested resource could not be found at the specified URL. See the detailed 404 guide for causes, fixes and SEO impact.

What is the difference between 301 and 302?

A 301 redirect is permanent — links and search engines should update to the new URL. A 302 signals a temporary move where the original URL stays canonical.

What does 503 mean?

HTTP 503 means the service is temporarily unavailable, usually because of maintenance or overload, and the client should retry after a delay.

What is the difference between 401 and 403?

401 means the server needs valid authentication credentials. 403 means it knows who you are and still refuses access — logging in again will not help.

What is the difference between 502 and 504?

Both come from a proxy talking to an upstream server: 502 means the upstream sent back an invalid response, 504 means it never answered within the timeout.

Which status codes matter most for SEO?

200 marks indexable pages, 301/308 transfer rankings on permanent moves, 404/410 remove dead URLs and 503 protects rankings during downtime when served with Retry-After.