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/HTTP

Response codes

HTTP response status codes indicate whether a specific HTTP request has been successfully completed. Responses are grouped in five classes: informational responses, successful responses, redirects, client errors, and servers errors. Status codes are defined by section 10 of RFC 2616.

Information responses

100 Continue: This interim response indicates that everything so far is OK and that the client should continue with the request or ignore it if it is already finished.
101 Switching Protocol: This code is sent in response to an Upgrade request header by the client, and indicates the protocol the server is switching too.
102 Processing (WebDAV): This code indicates that the server has received and is processing the request, but no response is available yet.

Successful responses

200 OK: The request has succeeded. The meaning of a success varies depending on the HTTP method:
GET: The resource has been fetched and is transmitted in the message body.
HEAD: The entity headers are in the message body.
POST: The resource describing the result of the action is transmitted in the message body.
TRACE: The message body contains the request message as received by the server
201 Created: The request has succeeded and a new resource has been created as a result of it. This is typically the response sent after a PUT request.
202 Accepted: The request has been received but not yet acted upon. It is non-committal, meaning that there is no way in HTTP to later send an asynchronous response indicating the outcome of processing the request. It is intended for cases where another process or server handles the request, or for batch processing.
203 Non-Authoritative Information: This response code means returned meta-information set is not exact set as available from the origin server, but collected from a local or a third party copy. Except this condition, 200 OK response should be preferred instead of this response.
204 No Content: There is no content to send for this request, but the headers may be useful. The user-agent may update its cached headers for this resource with the new ones.
205 Reset Content: This response code is sent after accomplishing request to tell user agent reset document view which sent this request.
206 Partial Content: This response code is used because of range header sent by the client to separate download into multiple streams.
207 Multi-Status (WebDAV): A Multi-Status response conveys information about multiple resources in situations where multiple status codes might be appropriate.
208 Multi-Status (WebDAV): Used inside a DAV: propstat response element to avoid enumerating the internal members of multiple bindings to the same collection repeatedly.
226 IM Used (HTTP Delta encoding): The server has fulfilled a GET request for the resource, and the response is a representation of the result of one or more instance-manipulations applied to the current instance.

Redirection messages

300 Multiple Choice: The request has more than one possible response. The user-agent or user should choose one of them. There is no standardized way of choosing one of the responses.
301 Moved Permanently: This response code means that the URI of the requested resource has been changed. Probably, the new URI would be given in the response.
302 Found: This response code means that the URI of requested resource has been changed temporarily. New changes in the URI might be made in the future. Therefore, this same URI should be used by the client in future requests.
303 See Other: The server sent this response to direct the client to get the requested resource at another URI with a GET request.
304 Not Modified: This is used for caching purposes. It tells the client that the response has not been modified, so the client can continue to use the same cached version of the response.
305 Use Proxy: Was defined in a previous version of the HTTP specification to indicate that a requested response must be accessed by a proxy. It has been deprecated due to security concerns regarding in-band configuration of a proxy.
306 unused: This response code is no longer used, it is just reserved currently. It was used in a previous version of the HTTP 1.1 specification.
307 Temporary Redirect: The server sends this response to direct the client to get the requested resource at another URI with same method that was used in the prior request. This has the same semantics as the 302 Found HTTP response code, with the exception that the user agent must not change the HTTP method used: If a POST was used in the first request, a POST must be used in the second request.
308 Permanent Redirect: This means that the resource is now permanently located at another URI, specified by the Location: HTTP Response header. This has the same semantics as the 301 Moved Permanently HTTP response code, with the exception that the user agent must not change the HTTP method used: If a POST was used in the first request, a POST must be used in the second request.

Client error responses

400 Bad Request: This response means that server could not understand the request due to invalid syntax.
401 Unauthorized: Although the HTTP standard specifies "unauthorized", semantically this response means "unauthenticated". That is, the client must authenticate itself to get the requested response.
402 Payment Required: This response code is reserved for future use. Initial aim for creating this code was using it for digital payment systems however this is not used currently.
403 Forbidden: The client does not have access rights to the content, i.e. they are unauthorized, so server is rejecting to give proper response. Unlike 401, the client's identity is known to the server.
404 Not Found: The server can not find requested resource. In the browser, this means the URL is not recognized. In an API, this can also mean that the endpoint is valid but the resource itself does not exist. Servers may also send this response instead of 403 to hide the existence of a resource from an unauthorized client. This response code is probably the most famous one due to its frequent occurence on the web.
405 Method Not Allowed: The request method is known by the server but has been disabled and cannot be used. For example, an API may forbid DELETE-ing a resource. The two mandatory methods, GET and HEAD, must never be disabled and should not return this error code.
406 Not Acceptable: This response is sent when the web server, after performing server-driven content negotiation, doesn't find any content following the criteria given by the user agent.
407 Proxy Authentication Required: This is similar to 401 but authentication is needed to be done by a proxy.
408 Request Timeout: This response is sent on an idle connection by some servers, even without any previous request by the client. It means that the server would like to shut down this unused connection. This response is used much more since some browsers, like Chrome, Firefox 27+, or IE9, use HTTP pre-connection mechanisms to speed up surfing. Also note that some servers merely shut down the connection without sending this message.
409 Conflict: This response is sent when a request conflicts with the current state of the server.
410 Gone: This response would be sent when the requested content has been permenantly deleted from server, with no forwarding address. Clients are expected to remove their caches and links to the resource. The HTTP specification intends this status code to be used for "limited-time, promotional services". APIs should not feel compelled to indicate resources that have been deleted with this status code.
411 Length Required: Server rejected the request because the Content-Length header field is not defined and the server requires it.
412 Precondition Failed: The client has indicated preconditions in its headers which the server does not meet.
413 Payload Too Large: Request entity is larger than limits defined by server; the server might close the connection or return an Retry-After header field.
414 URI Too Long: The URI requested by the client is longer than the server is willing to interpret.
415 Unsupported Media Type: The media format of the requested data is not supported by the server, so the server is rejecting the request.
416 Requested Range Not Satisfiable: The range specified by the Range header field in the request can't be fulfilled; it's possible that the range is outside the size of the target URI's data.
417 Expectation Failed: This response code means the expectation indicated by the Expect request header field can't be met by the server.
418 I'm a teapot: The server refuses the attempt to brew coffee with a teapot.
421 Misdirected Request: The request was directed at a server that is not able to produce a response. This can be sent by a server that is not configured to produce responses for the combination of scheme and authority that are included in the request URI.
422 Unprocessable Entity (WebDAV): The request was well-formed but was unable to be followed due to semantic errors.
423 Locked (WebDAV): The resource that is being accessed is locked.
424 Failed Dependency (WebDAV): The request failed due to failure of a previous request.
426 Upgrade Required: The server refuses to perform the request using the current protocol but might be willing to do so after the client upgrades to a different protocol. The server sends an Upgrade header in a 426 response to indicate the required protocol(s).
428 Precondition Required: 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.
429 Too Many Requests: The user has sent too many requests in a given amount of time ("rate limiting").
431 Request Header Fields Too Large: The server is unwilling to process the request because its header fields are too large. The request MAY be resubmitted after reducing the size of the request header fields.
451 Unavailable For Legal Reasons: The user requests an illegal resource, such as a web page censored by a government.

Server error responses