510 Not Extended

The HyperText Transfer Protocol (HTTP) 510 Not Extended response status code is sent in the context of the HTTP Extension Framework, defined in RFC 2774.

In that specification a client may send a request that contains an extension declaration, that describes the extension to be used. If the server receives such a request, but any described extensions are not supported for the request, then the server responds with the 510 status code.

510 Not Extended