Duo's unique feature is Knock Knock, which gives you a preview of who is calling by firing up the camera on the other end of the line. If you're initiating the call, you'll see a little notice that says your video is visible, which means the other person can see what you're doing right at that moment in real time. Android users can see Knock Knock regardless of whether Duo is opened or not (like on the lock screen). On the iPhone though, you'll only see it if you're in the app. Otherwise, you'll just get a little notification saying someone's calling you. Google's rationale for this is that Knock Knock already gets you smiling before the call starts. Of course, that's assuming you actually like/want to speak to the other person who is on the other line.
You can go and download this app now on play store for android users. Click here to download.
After downloading setting up your Google Duo is very easy.
Setting Up Your Google Duo App
=> Launch the app and click on I AGREE
Wooohooo! After performing the above steps you are ready to use Google Duo. I hope you enjoy this app. Don't leave your feedback in the comment box if you are already using this app.