The instant messaging race is a close one indeed and it appears that you can communicate instantly on almost every app available. iOS users often stick with iMessage, Western Europe and the United Stated love WhatsApp, but Viber appears to be dominating in Eastern Europe and Asia.
Its Android version is often updated, and it keeps up with other messaging apps. It can be synced with your Contacts list, so that you can immediately see who is using Viber. It allows you to do almost everything you can think of: instant chat, make audio and video calls, and use special Viber stickers. Stickers are generally not free, but there are plenty of free ones to try out.
The Discover section is used to access public chats created by other users and websites, but that function didn't really fully catch up with users yet. You can also buy Viber Credit and use it to make regular international phone calls, but keep in mind that you will need to have a stable Internet connection for that purpose.
Incoming messages when the app is running in the background can pop-up in two different ways: as a window in the middle of the screen or as a regular notification. Each one lightens up your screen, so they are hard to miss. It can be observed that the messages sometimes only arrive when you unlock your phone, which could be a major problem. You can also choose whether you want to download photos automatically and to restrict data usage for users with limited data plans!
All in all, it's a great and functional instant messaging app and the numbers are there to speak for it: it has more than 500 million downloads on the Play Store! There are plugins from YouTube, GIPHy, GAMEE, and so on, which can be used to really add to the overall experience.
• It's simple and easy to use
• The quality of calls is good
• You can tweak the app to restrict data usage
• Plenty of chat plugins to personalize your chat
• Messages sometimes only appear after you unlock your phone's screen