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.
- HTTP authentication
- 403 Forbidden
- 407 Proxy Authentication Required