Viber allows the users to make hassle-free video and voice calls with no added amount. You can make HD-quality calls, but for that you will need the other person to have the latest version of the app installed in their device.
A feature that sets Viber apart from the other apps that allow free calling feature is the fact that you can use Viber to make calls to people who do not have Viber. This includes mobile as well as landline numbers. This feature, however, will require the caller to make use of Viber credits.
The constant stream of notification can be bothersome and Viber has taken steps to prevent this. With the latest Android 5.3 update, Viber allows the users to avail the smart notification feature, where several notifications are clubbed together and sent at a set interval.
Viber also has a feature where users can easily block the person they do not wish to communicate with. The user can open a communication with the person they want to block and click on menu. The option comes up and one can simply click on it and block the person.
Viber saw a 200% growth in users this year, surpassing WhatsApp and Skype. It has over 500 million users in over 193 countries.