>>> 1xx: Informational - Request received, continuing process.
- 100 Continue: The server has received the request headers, and the client should proceed to send the request body.
- 101 Switching Protocols: The requester has asked the server to switch protocols and the server is acknowledging that it will do so.
>>> 2xx: Success - The request was successfully received, understood, and accepted.
- 200 OK: The request has succeeded.
- 201 Created: The request has been fulfilled and has resulted in one or more new resources being created.
- 202 Accepted: The request has been accepted for processing, but the processing has not been completed.
- 204 No Content: The server successfully processed the request, but is not returning any content.
>>> 3xx: Redirection - Further action needs to be taken to complete the request.
- 301 Moved Permanently: The resource requested has been definitively moved to the URL given by the Location headers.
- 302 Found: The resource requested is temporarily under a different URL.
- 304 Not Modified: Indicates that the resource has not been modified since the version specified by the request headers.
>>> 4xx: Client Error - The request contains bad syntax or cannot be fulfilled.
- 400 Bad Request: The server cannot or will not process the request due to an apparent client error.
- 401 Unauthorized: Authentication is required and has failed or has not yet been provided.
- 403 Forbidden: The request was valid, but the server is refusing action.
- 404 Not Found: The requested resource could not be found.
- 405 Method Not Allowed: A request method is not supported for the requested resource.
- 409 Conflict: Indicates that the request could not be processed because of conflict in the request, such as an edit conflict.
>>> 5xx: Server Error - The server failed to fulfill an apparently valid request.
- 500 Internal Server Error: A generic error message, given when an unexpected condition was encountered.
- 501 Not Implemented: The server either does not recognize the request method, or it lacks the ability to fulfill the request.
- 502 Bad Gateway: The server was acting as a gateway or proxy and received an invalid response from the upstream server.
- 503 Service Unavailable: The server is currently unavailable (because it is overloaded or down for maintenance).
- 504 Gateway Timeout: The server was acting as a gateway or proxy and did not receive a timely response from the upstream server.
These codes are part of the HTTP/1.1 standard, and their definitions can be found in RFC 2616 and its successors.
