4×× CLIENT ERROR
The server understood the request but refuses to authorize it.
A server that wishes to make public why the request has been forbidden can describe that reason in the response payload (if any).
If authentication credentials were provided in the request, the server considers them insufficient to grant access. The client SHOULD NOT automatically repeat the request with the same credentials. The client MAY repeat the request with new or different credentials. However, a request might be forbidden for reasons unrelated to the credentials.
An origin server that wishes to “hide” the current existence of a forbidden target resource MAY instead respond with a status code of 404 Not Found.
403 FORBIDDEN Source: RFC7231 Section 6.5.3
403 CODE REFERENCES
Rails HTTP Status Symbol
Go HTTP Status Constant
Symfony HTTP Status Constant
Python2 HTTP Status Constant
Python3+ HTTP Status Constant
Python3.5+ HTTP Status Constant