According to examples, an apparatus may include a processor that may receive a request from a first device for an authentication token for access to a service, determine whether the first device is authorized to receive the authentication token for access to the service, and based on a determination that the first device is authorized to receive the authentication token for access to the service, generate a machine-readable code including the authentication token that a second device is to use for access to the service by the second device. The processor may also send the generated machine-readable code to the first device. The first device may display the machine-readable code and the second device may use a captured image of the machine-readable code to establish an authenticated session to the service on the second device.