HTTP Status CodesFriday, January 20, 2017 3:01 AM
This is a list of Hypertext Transfer Protocol (HTTP) response status codes. It includes codes from IETF internet standards, other IETF RFCs, other specifications, and some additional commonly used codes. The first digit of the status code specifies one of five classes of response; an HTTP client must recognise these five classes at a minimum. The phrases used are the standard wordings, but any human-readable alternative can be provided. Unless otherwise stated, the status code is part of the HTTP/1.1 standard.
The Internet Assigned Numbers Authority (IANA) maintains the official registry of HTTP status codes.
Microsoft IIS sometimes uses additional decimal sub-codes to provide more specific information, but not all of those are here (note that these sub-codes only appear in the response payload and in documentation; not in the place of an actual HTTP status code).
Request received, continuing process.
This class of status code indicates a provisional response, consisting only of the Status-Line and optional headers, and is terminated by an empty line. Since HTTP/1.0 did not define any 1xx status codes, servers must not send a 1xx response to an HTTP/1.0 client except under experimental conditions.
This class of status codes indicates the action requested by the client was received, understood, accepted, and processed successfully.
This class of status code indicates the client must take additional action to complete the request. Many of these status codes are used in URL redirection.
A user agent may carry out the additional action with no user interaction only if the method used in the second request is GET or HEAD. A user agent may automatically redirect a request. A user agent should detect and intervene to prevent cyclical redirects.
The 4xx class of status code 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.
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.
The following codes are not specified by any RFC, but are used by third-party services to provide semantic or RESTful error responses:
The Internet Information Services expands the 4xx error space to signal errors with the client's request.
The nginx web server software expands the 4xx error space to signal issues with the client's request. These are only used for logging purposes, no actual response is sent with these codes.
Cloudflare's reverse proxy service expands the 5xx series of errors space to signal issues with the origin server.
(Article from: https://en.wikipedia.org/wiki/List_of_HTTP_status_codes)