The server cannot or will not process the request due to an apparent client error (e.g., malformed request syntax, size too large, invalid request message framing, or deceptive request routing).
Indicates that the request could not be processed because of conflict in the request, such as an edit conflict between multiple simultaneous updates.
The server cannot meet the requirements of the Expect request-header field.
The request failed because it depended on another request and that request failed.
The request was valid, but the server is refusing action.
The user might not have the necessary permissions for a resource, or may need an account of some sort.
Indicates that the resource requested is no longer available and will not be available again.
This should be used when a resource has been intentionally removed and the resource should be purged. Upon receiving a 410 status code, the client should not request the resource in the future. Clients such as search engines should remove the resource from their indices. Most use cases do not require clients and search engines to purge the resource, and a "404 Not Found" may be used instead.
This code was defined in 1998 as one of the traditional IETF April Fools' jokes, in RFC 2324, Hyper Text Coffee Pot Control Protocol, and is not expected to be implemented by actual HTTP servers.
The RFC specifies this code should be returned by teapots requested to brew coffee. This HTTP status is used as an Easter egg in some websites, including Google.com.
The request did not specify the length of its content, which is required by the requested resource.
The resource that is being accessed is locked.
A request method is not supported for the requested resource; for example, a GET request on a form that requires data to be presented via POST, or a PUT request on a read-only resource.
The request was directed at a server that is not able to produce a response[53] (for example because of connection reuse).
The requested resource is capable of generating only content not acceptable according to the Accept headers sent in the request.
The requested resource could not be found but may be available in the future.
Subsequent requests by the client are permissible.
The request is larger than the server is willing or able to process. Previously called "Request Entity Too Large".
Reserved for future use.
The original intention was that this code might be used as part of some form of digital cash or micro-payment scheme, as proposed for example by GNU Taler, but that has not yet happened, and this code is not usually used. Google Developers API uses this status if a particular developer has exceeded the daily limit on requests
The server does not meet one of the preconditions that the requester put on the request.
The origin server requires the request to be conditional.
Intended to prevent the 'lost update' problem, where a client GETs a resource's state, modifies it, and PUTs it back to the server, when meanwhile a third party has modified the state on the server, leading to a conflict.
The client must first authenticate itself with the proxy.
The client has asked for a portion of the file (byte serving), but the server cannot supply that portion.
For example, if the client asked for a part of the file that lies beyond the end of the file. Called "Requested Range Not Satisfiable" previously.
The server is unwilling to process the request because either an individual header field, or all the header fields collectively, are too large.[
The server timed out waiting for the request.
According to HTTP specifications: "The client did not produce a request within the time that the server was prepared to wait. The client MAY repeat the request without modifications at any later time.
The user has sent too many requests in a given amount of time. Intended for use with rate-limiting schemes.
Similar to 403 Forbidden, but specifically for use when authentication is required and has failed or has not yet been provided.
The response must include a WWW-Authenticate header field containing a challenge applicable to the requested resource. See Basic access authentication and Digest access authentication. 401 semantically means "unauthenticated",[35] i.e. the user does not have the necessary credentials.
Note: Some sites issue HTTP 401 when an IP address is banned from the website (usually the website domain) and that specific address is refused permission to access a website.
A server operator has received a legal demand to deny access to a resource or to a set of resources that includes the requested resource.
The code 451 was chosen as a reference to the novel Fahrenheit 451.
The request was well-formed but was unable to be followed due to semantic errors.
The request entity has a media type which the server or resource does not support.
For example, the client uploads an image as image/svg+xml, but the server requires that images use a different format.
The client should switch to a different protocol such as TLS/1.0, given in the Upgrade header field.
The URI provided was too long for the server to process.
Often the result of too much data being encoded as a query-string of a GET request, in which case it should be converted to a POST request. Called "Request-URI Too Long" previously.
This class of status code is intended for situations in which the error seems to have been caused by the client.
Except when responding to a HEAD request, the server should include an entity containing an explanation of the error situation, and whether it is a temporary or permanent condition. These status codes are applicable to any request method. User agents should display any included entity to the user.