HTTP 響應狀態(tài)代碼指示特定的 HTTP 請求是否已成功完成。響應分為五類：信息響應，成功響應，重定向，客戶端錯誤和服務器錯誤。狀態(tài)碼由 RFC 2616 的第10部分定義。

信息回應

100 Continue這個臨時響應表明，到目前為止，所有事情都可以確定，并且客戶端應該繼續(xù)請求或者在請求已經完成時忽略它。101 Switching Protocol此代碼是為了響應Upgrade客戶端的請求標頭而發(fā)送的，并指示服務器也正在切換的協議。102 Processing（WebDAV）此代碼表示服務器已接收并正在處理該請求，但尚未提供任何響應。

成功的回應

200 OK該請求已成功。成功的意義取決于 HTTP 方法：

GET：資源已被提取并在消息體中傳輸。

HEAD：實體頭部位于消息體中。

POST：描述操作結果的資源在消息主體中傳輸。

TRACE：消息正文包含服務器接收到的請求消息201 Created請求已成功并且由于此請求已創(chuàng)建新資源。這通常是在PUT請求后發(fā)送的響應。202 Accepted該請求已收到，但尚未執(zhí)行。它是非承諾的，這意味著HTTP中沒有辦法稍后發(fā)送指示處理請求結果的異步響應。它適用于其他進程或服務器處理請求或批處理的情況。203 Non-Authoritative Information此響應代碼意味著返回的元信息集不是從原始服務器準確設置的，而是從本地或第三方副本收集的。除了這種情況外，應該優(yōu)先選擇200 OK響應而不是此響應。204 No Content沒有要發(fā)送此請求的內容，但標題可能很有用。用戶代理可以用新的更新它的這個資源的緩存標題。205 Reset Content此響應代碼在完成請求以告知發(fā)送此請求的用戶代理重置文檔視圖后發(fā)送。206 Partial Content使用此響應代碼是因為客戶端發(fā)送的范圍標題將分隔下載到多個流中。207 Multi-Status（WebDAV）在多個狀態(tài)代碼可能適用的情況下，多狀態(tài)響應傳達有關多個資源的信息。208 Multi-Status（WebDAV）在DAV：propstat響應元素中使用，以避免重復枚舉多個綁定的內部成員到同一個集合。226 IM Used（HTTP Delta編碼）服務器已經完成了對資源的GET請求，并且響應是應用于當前實例的一個或多個實例操作結果的表示。

重定向消息

300 Multiple ChoiceThe request has more than one possible responses. User-agent or user should choose one of them. There is no standardized way to choose one of the responses.301 Moved PermanentlyThis response code means that URI of requested resource has been changed. Probably, new URI would be given in the response.302 FoundThis response code means that 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 OtherServer sent this response to directing client to get requested resource to another URI with an GET request.304 Not ModifiedThis is used for caching purposes. It is telling to client that response has not been modified. So, client can continue to use same cached version of response.305 Use ProxyWas 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 unusedThis 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 RedirectServer sent this response to directing client to get requested resource to another URI with same method that used prior request. This has the same semantic than 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 RedirectThis 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 RequestThis response means that server could not understand the request due to invalid syntax.401 UnauthorizedAlthough the HTTP standard specifies "unauthorized", semantically this response means "unauthenticated". That is, the client must authenticate itself to get the requested response.402 Payment RequiredThis 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 ForbiddenThe 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 FoundThe 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 AllowedThe 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 AcceptableThis 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 RequiredThis is similar to 401 but authentication is needed to be done by a proxy.408 Request TimeoutThis 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 ConflictThis response is sent when a request conflicts with the current state of the server.410 GoneThis 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 RequiredServer rejected the request because the Content-Length header field is not defined and the server requires it.412 Precondition FailedThe client has indicated preconditions in its headers which the server does not meet.413 Payload Too LargeRequest entity is larger than limits defined by server; the server might close the connection or return an Retry-After header field.414 URI Too LongThe URI requested by the client is longer than the server is willing to interpret.415 Unsupported Media TypeThe media format of the requested data is not supported by the server, so the server is rejecting the request.416 Requested Range Not SatisfiableThe 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 FailedThis response code means the expectation indicated by the Expect request header field can't be met by the server.418 I'm a teapotThe server refuses the attempt to brew coffee with a teapot.421 Misdirected RequestThe 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 RequiredThe 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 RequiredThe 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 RequestsThe user has sent too many requests in a given amount of time ("rate limiting").431 Request Header Fields Too LargeThe 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 ReasonsThe user requests an illegal resource, such as a web page censored by a government.

Server error responses

500 Internal Server ErrorThe server has encountered a situation it doesn't know how to handle.501 Not ImplementedThe request method is not supported by the server and cannot be handled. The only methods that servers are required to support (and therefore that must not return this code) are GET and HEAD.502 Bad GatewayThis error response means that the server, while working as a gateway to get a response needed to handle the request, got an invalid response.503 Service UnavailableThe server is not ready to handle the request. Common causes are a server that is down for maintenance or that is overloaded. Note that together with this response, a user-friendly page explaining the problem should be sent. This responses should be used for temporary conditions and the Retry-After: HTTP header should, if possible, contain the estimated time before the recovery of the service. The webmaster must also take care about the caching-related headers that are sent along with this response, as these temporary condition responses should usually not be cached.504 Gateway TimeoutThis error response is given when the server is acting as a gateway and cannot get a response in time.505 HTTP Version Not SupportedThe HTTP version used in the request is not supported by the server.506 Variant Also NegotiatesThe server has an internal configuration error: transparent content negotiation for the request results in a circular reference.507 Insufficient StorageThe server has an internal configuration error: the chosen variant resource is configured to engage in transparent content negotiation itself, and is therefore not a proper end point in the negotiation process.508 Loop Detected (WebDAV)The server detected an infinite loop while processing the request.510 Not ExtendedFurther extensions to the request are required for the server to fulfill it.511 Network Authentication RequiredThe 511 status code indicates that the client needs to authenticate to gain network access.

See also

• List of HTTP status codes on Wikipedia

• IANA official registry of HTTP status codes

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https://developer.mozilla.org/en-US/docs/Web/HTTP/Status