This heavily depends on country of residence. While I had been living in Serbia, there was one king - Viber. I've heard of WhatsApp back then but didn't know a

This heavily depends on country of residence. While I had been living in Serbia, there was one king - Viber. I've heard of WhatsApp back then but didn't know a single person using it. In Germany it's vice versa - the king is WhatsApp, nobody heard of Viber.