As of 2018, there are over a billion registered users on the network. In addition to instant messaging it allows users to exchange media such as images and video records, and also provides a paid international landline and mobile calling service called Viber Out. Users are registered and identified through a cellular telephone number, although the service is accessible on desktop platforms without needing mobile connectivity.

Viber, or Rakuten Viber, is a cross-platform voice over IP (VoIP) and instant messaging (IM) software application owned by Japanese multinational company Rakuten, provided as freeware for the Android, iOS, Microsoft Windows, macOS and Linux platforms.