Google duo a very fabulous vedio calling app.
No need to registration in this app.
This app is totally Ads free. The voice and vedio quality in this is perfect.This app also easily free available on play store.The size of this app is between 10mb to 15 mb.
It work better even on slow internet connection.
It also better work in international calls.
On various Device it is pre-install by google.
We can also invite to those ones who are not using app . This app is really a great vedio calling apps as we compare with other. I am satisfied with this app.There are very less disadvantage in this app. So Guys must use this app and enjoy its features.