Ranked in these QuestionsQuestion Ranking
Pro No need to create an account or add contacts
One of the best things about Viber is how it handles setup and sending messages. Viber uses your existing number as your ID, so you don't need to create a separate Viber account.
Pro Desktop apps allow texting, calling and enables transferring calls between devices
Viber has native apps for both Windows and Mac that allow you to send and receive messages from your desktop. You can also use the desktop to make and receive calls. Synchronizes between all devices you are using Viber on. Allows transferring calls between devices.
Pro Completely free and ad-less
Viber uses data connection and the app is free. There are also no advertisements.
Pro Supports voice calls
Viber has really well implemented voice tech. It has comparable quality to Skype and you can even tranfer calls from your phone to your desktop seamlessly.
Pro Supports 200 person group chat
Viber allows creating groups of up to 200 people on the Android version of Viber. It also has a cool "smart notifications" feature to prevent being overwhelmed with notifications if a lot of people are active in a chat group.
Pro Clean interface
The interface is simple, functional and intuitive.
Pro See who of your contacts is using Viber quickly
Viber is tied to your phone number so it can quickly see who else in your contacts list is using the application.
Pro Combines cellular and data messaging
This has an advantage in that if you text someone who uses Viber it will be free, if not it will just revert to SMS. This means you can replace your standard messaging app with Viber as well.
Pro Public chats
It's possible to be a fly on the wall on other group or one-to-one chats that have been opened up to the public. These public chats are often promotional chats with celebrities.
Pro Android Wear support
Viber includes Android Wear support on Android 4.3 or higher and Viber 5.3 or higher.
Pro Same protocol as used in Signal
Viber's protocol uses the same concepts of the "double ratchet" protocol used in Open Whisper Systems Signal application.
Pro Insight and well documented encryption
Pro Keys only on device
Starting with Viber 6.0 the encryption keys are stored only on the clients themselves, not even Viber itself has access to them.
Con Shady company
There is zero information on the founders of Viber, which leads to some questions as to who is behind a platform that has access to a large swath of user information.
Con The company evades U. S. tax
Adding to the fact that there is no founder information, the company also uses a tax haven address in order to avoid paying US taxes despite being registered in Delaware.
Con Has multiple a security vulnerabilities
EFF gave Viber's security 1 out of 7 points in November, 2014. It deducted points because the provider is capable of reading encrypted messages, there's no way to verify contacts identities, past communications are not secure if encryption keys are stolen, the code is not open to independent reviews, the security design is not properly documented and there has not been a recent code audit.