4×× Client Error

406 Not Acceptable

The target resource does not have a current representation that would be acceptable to the user agent, according to the proactive negotiation header fields received in the request1, and the server is unwilling to supply a default representation.

The server SHOULD generate a payload containing a list of available representation characteristics and corresponding resource identifiers from which the user or user agent can choose the one most appropriate. A user agent MAY automatically select the most appropriate choice from that list. However, this specification does not define any standard for such automatic selection, as described in RFC7231 Section 6.4.1.