HTTP response status

The status code is a 3-digit number:

• 1xx (Informational): Request received, server is continuing the process.
• 2xx (Success): The request was successfully received, understood, accepted and serviced.
• 3xx (Redirection): Further action must be taken in order to complete the request.
• 4xx (Client Error): The request contains bad syntax or cannot be understood.
• 5xx (Server Error): The server failed to fulfill an apparently valid request.

Some commonly encountered status codes are:

• 100 Continue: The server received the request and in the process of giving the response.
• 200 OK: The request is fulfilled.
• 301 Move Permanently: The resource requested for has been permanently moved to a new location. The URL of the new location is given in the response header called Location. The client should issue a new request to the new location. Application should update all references to this new location.
• 302 Found & Redirect (or Move Temporarily): Same as 301, but the new location is temporarily in nature. The client should issue a new request, but applications need not update the references.
• 304 Not Modified: In response to the If-Modified-Since conditional GET request, the server notifies that the resource requested has not been modified.
• 400 Bad Request: Server could not interpret or understand the request, probably syntax error in the request message.
• 401 Authentication Required: The requested resource is protected, and require client’s credential (username/password). The client should re-submit the request with his credential (username/password).
• 403 Forbidden: Server refuses to supply the resource, regardless of identity of client.
• 404 Not Found: The requested resource cannot be found in the server.
• 405 Method Not Allowed: The request method used, e.g., POST, PUT, DELETE, is a valid method. However, the server does not allow that method for the resource requested.
• 408 Request Timeout:
• 414 Request URI too Large:
• 500 Internal Server Error: Server is confused, often caused by an error in the server-side program responding to the request.
• 501 Method Not Implemented: The request method used is invalid (could be caused by a typing error, e.g., "GET" misspell as "Get").
• 502 Bad Gateway: Proxy or Gateway indicates that it receives a bad response from the upstream server.
• 503 Service Unavailable: Server cannot response due to overloading or maintenance. The client can try again later.
• 504 Gateway Timeout: Proxy or Gateway indicates that it receives a timeout from an upstream server.

原文地址：https://www.cnblogs.com/ellie-test/p/11672592.html