The service claimed 140M last December, 100M in September, 70M in May and 50M in February 2012. Recently, Viber claimed to record a rate of 400,000 new followers every day.
The Viber app is currently available on iOS, Android, Blackberry, Windows Phone, and Symbian.
Among its competitors: the Line application, popular in Japan, claims 100M users. More popular in Europe, the Whatsapp application has, for its part, nearly 250M users. Finally, Skype would have 800M subscribers, including 280M unique users each month.