http 4xx,5xx Server error

引用自 wikipedia https://en.wikipedia.org/wiki/List_of_HTTP_status_codes

4xx Client errors

The 4xx class of status codes is intended for situations in which the client seems to have erred. 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. [31]

400 Bad Request

The server cannot or will not process the request due to an apparent client error (e.g., malformed request syntax, too large size, invalid request message framing, or deceptive request routing). [32]

401 Unauthorized ( RFC 7235)

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. [33]  401 semantically means   "unauthenticated", [34]  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.

402 Payment Required

Reserved for future use. The original intention was that this code might be used as part of some form of   digital cash  or   micropayment  scheme, but that has not 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. [35]

403 Forbidden

The request was valid, but the server is refusing action. The user might not have the necessary permissions for a resource.

404 Not Found

The requested resource could not be found but may be available in the future. Subsequent requests by the client are permissible. [36]

405 Method Not Allowed

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.

406 Not Acceptable

The requested resource is capable of generating only content not acceptable according to the Accept headers sent in the request. [37]  See   Content negotiation.

407 Proxy Authentication Required ( RFC 7235)

The client must first authenticate itself with the   proxy. [38]

408 Request Time-out

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." [39]

409 Conflict

Indicates that the request could not be processed because of conflict in the request, such as an   edit conflict  between multiple simultaneous updates.

410 Gone

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. [40]  Most use cases do not require clients and search engines to purge the resource, and a "404 Not Found" may be used instead.

411 Length Required

The request did not specify the length of its content, which is required by the requested resource. [41]

412 Precondition Failed ( RFC 7232)

The server does not meet one of the preconditions that the requester put on the request. [42]

413 Payload Too Large ( RFC 7231)

The request is larger than the server is willing or able to process. Previously called "Request Entity Too Large". [43]

414 URI Too Long ( RFC 7231)

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. [44]  Called "Request-URI Too Long" previously. [45]

415 Unsupported Media Type

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.

416 Range Not Satisfiable ( RFC 7233)

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. [46]  Called "Requested Range Not Satisfiable" previously. [47]

417 Expectation Failed

The server cannot meet the requirements of the Expect request-header field. [48]

418 I'm a teapot ( RFC 2324)

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. [49]  This HTTP status is used as an   Easter egg  in some websites, including   Google.com. [50]

421 Misdirected Request ( RFC 7540)

The request was directed at a server that is not able to produce a response (for example because a connection reuse). [51]

422 Unprocessable Entity (WebDAV;   RFC 4918)

The request was well-formed but was unable to be followed due to semantic errors. [15]

423 Locked (WebDAV;   RFC 4918)

The resource that is being accessed is locked. [15]

424 Failed Dependency (WebDAV;   RFC 4918)

The request failed due to failure of a previous request (e.g., a PROPPATCH). [15]

426 Upgrade Required

The client should switch to a different protocol such as   TLS/1.0, given in the   Upgrade header  field. [52]

428 Precondition Required ( RFC 6585)

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." [53]

429 Too Many Requests ( RFC 6585)

The user has sent too many requests in a given amount of time. Intended for use with   rate-limiting  schemes. [53]

431 Request Header Fields Too Large ( RFC 6585)

The server is unwilling to process the request because either an individual header field, or all the header fields collectively, are too large. [53]

451 Unavailable For Legal Reasons  ( RFC 7725)

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. [54]  The code 451 was chosen as a reference to the novel   Fahrenheit 451.

5xx Server error[edit]

The server failed to fulfill an apparently valid request

Response status codes beginning with the digit "5" indicate cases in which the server is aware that it has encountered an error or is otherwise incapable of performing the request. Except when responding to a HEAD request, the server should include an entity containing an explanation of the error situation, and indicate whether it is a temporary or permanent condition. Likewise, user agents should display any included entity to the user. These response codes are applicable to any request method.[56]

500 Internal Server Error

A generic error message, given when an unexpected condition was encountered and no more specific message is suitable. [57]

501 Not Implemented

The server either does not recognize the request method, or it lacks the ability to fulfill the request. Usually this implies future availability (e.g., a new feature of a web-service API). [58]

502 Bad Gateway

The server was acting as a   gateway  or proxy and received an invalid response from the upstream server. [59]

503 Service Unavailable

The server is currently unavailable (because it is overloaded or down for maintenance). Generally, this is a temporary state. [60]

504 Gateway Time-out

The server was acting as a gateway or proxy and did not receive a timely response from the upstream server. [61]

505 HTTP Version Not Supported

The server does not support the HTTP protocol version used in the request. [62]

506 Variant Also Negotiates ( RFC 2295)

Transparent   content negotiation  for the request results in a   circular reference. [63]

507 Insufficient Storage (WebDAV;   RFC 4918)

The server is unable to store the representation needed to complete the request. [15]

508 Loop Detected (WebDAV;   RFC 5842)

The server detected an infinite loop while processing the request (sent in lieu of   208 Already Reported).

510 Not Extended ( RFC 2774)

Further extensions to the request are required for the server to fulfill it. [64]

511 Network Authentication Required ( RFC 6585)

The client needs to authenticate to gain network access. Intended for use by intercepting proxies used to control access to the network (e.g., "captive portals" used to require agreement to Terms of Service before granting full Internet access via a Wi-Fi hotspot).[53]

根據平時常用的幾個，總結下：

400 Bad Request 請求參數

401 Unauthorized 同403類似，差別是适用需要授權票據(http header Authorization)，但票據校驗失敗或未提供的場景

403 Forbidden 禁止通路，使用者沒有對資源通路需要的權限

404 Not Foud 請求位址不存在對應處理器映射

500 Internal Server Error作為伺服器服務報錯/異常的代碼；

501 Not Implement 服務未實作的方法，如服務端不支援PATCH請求，用戶端PATCH類型請求，就會傳回的狀态碼

502 Bad Gateway 通常是未釋出好，或者主機位址未正确解析（如今天遇到的移動端忘記配Host就通路API）

503 Service Unavailable 目前無法通路，展現的是一種臨時的狀态

504 Gateway Timeout請求服務逾時未傳回