http 501 Not Implemented

5×× Server Error

501 Not Implemented

The server does not support the functionality required to fulfill the request.
This is the appropriate response when the server does not recognize the request method and is not capable of supporting it for any resource.
A 501 response is cacheable by default; i.e., unless otherwise indicated by the method definition or explicit cache controls1.

• 1 Calculating Heuristic Freshness RFC7234 Section 4.2.2
• Source: RFC7231 Section 6.6.2

501 Code References

Rails HTTP Status Symbol :not_implemented
Go HTTP Status Constant http.StatusNotImplemented
Symfony HTTP Status Constant Response::HTTP_NOT_IMPLEMENTED
Python2 HTTP Status Constant httplib.NOT_IMPLEMENTED
Python3 HTTP Status Constant http.client.NOT_IMPLEMENTED
Python3.5 HTTP Status Constant http.HTTPStatus.NOT_IMPLEMENTED