Wikipedia
Viber
Viber is an instant messaging and Voice over IP (VoIP) app for smartphones developed by Viber Media. In addition to instant messaging, users can exchange images, video and audio media messages. The client software is available for Apple iOS, Android, Windows Phone, BlackBerry OS, Nokia Series 40, Symbian, Bada, Mac OS, and Microsoft Windows. A 64-bit Linux version is available in both .deb ( Debian and Ubuntu) and .rpm ( Fedora and openSUSE) package formats. It first requires installation on a phone in order to work on a desktop operating system environment. , Viber had over 100 million monthly active users and 280 million registered users.