Appendix D

HTTP/1.1 Status Codes and Reason Phrases (IETF RFC 2616)

The status code element is a three-digit integer result code of the attempt to understand and satisfy the request. The reason phrase exists for the sole purpose of providing a textual description associated with the numeric status code, done out of deference to earlier Internet application protocols that were more frequently used with interactive text clients. A client should ignore the content of the reason phrase. The reason phrases listed are only recommendations and may be replaced by local equivalents without affecting the protocol.

The first digit of the status code defines the class of response. The last two digits do not have any categorization role. There are five values for the first digit:

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

  Response Class	Status Code	Reason Phrase
  1xx: Informational: Request received, continuing process	100	Continue
  	101	Switching protocols
  2xx: Success: The action was successfully received, understood, and accepted	200	OK
  	201	Created
  	202	Accepted
  	203	Nonauthoritative
  	204	No Content
  	205	Reset Content
  	206	Partial Content
  3xx: Redirection: Further action must be taken in order to complete the request	300	Multiple Choices
  	301	Moved Permanently
  	302	Found
  	303	See Other
  	304	Not Modified
  	305	Use Proxy
  	307	Temporary Redirect
  4xx: Client Error: The request contains bad syntax or cannot be fulfilled	400	Bad Request
  	401	Unauthorized
  	402	Payment Required
  	403	Forbidden
  	404	Not Found
  	405	Method Not Allowed
  	406	Not Acceptable
  	407	Proxy Authentication Required
  	408	Request Time-out
  	409	Conflict
  	410	Gone
  4xx: Client Error: The request contains bad syntax or cannot be fulfilled	411	Length Required
  	412	Precondition Failed
  	413	Request Entity Too Large
  	414	URI Too Long
  	415	Unsupported Media Type
  	416	Request range not satisfiable
  	417	Expectation Failed
  5xx: Server Error: The server failed to fulfill an apparently valid request	500	Internal Server Error
  	501	Not Implemented
  	502	Bad Gateway
  	503	Service Unavailable
  	504	Gateway Time-out
  	505	HTTP Version not supported

HTTP status codes are extensible. HTTP applications are not required to understand the meaning of all registered status codes, although such understanding is obviously desirable. However, applications must understand the class of any status code, as indicated by the first digit, and treat any unrecognized response as being equivalent to the x00 status code of that class, with the exception that an unrecognized response must not be cached. For example, if an unrecognized status code of 431 is received by the client, it can safely assume that there was something wrong with its request and treat the response as if it had received a 400 status code.

For a complete understanding of the status codes and their response phases, it is recommended that you consult the IETF RFC 2616 publication.