Unauthorized
The HTTP 401 Unauthorized
response status code indicates that the client request has not been
completed because it lacks valid authentication credentials for the requested resource.
This status code is sent with an HTTP WWW-Authenticate
response header that contains
information on how the client can request for the resource again after prompting the user for authentication credentials.
This status code is similar to the 403 Forbidden
status code, except that in situations resulting in this
status code, user authentication can allow access to the resource.
Source: https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/401