Viber is a messenger and Voice over IP app for phones and desktop. In addition to simple text messages, users can send images, video and audio messages to other contacts. The UI shows current messages, recent calls, contacts and other options. Users register with their own phone number, and scrapes your personal contacts for other Viber users. A feature release in December 2013, dubbed Viber Out, lets users have the option to call mobile and landline numbers, giving the ability to contact people that may not be Viber users.