Systems, processes and devices identify content on the Internet or another network. A media player device receives an identifier that is uniquely associated with a particular media program. The identifier is submitted from the media player device to a registry service accessible via the digital network to thereby locate the particular media program for playback by the media player device or for performing other actions, and a message containing the identifier is initiated and transmitted to a recipient media player device via the digital network to thereby allow the recipient media player device to locate the same particular media program on the digital network using the identifier.