We have previously reported on Google Duo support on Chromebooks. Many Duo advocates of Google’s video app did feel a little left out and hoped that they too could access it in much the same way. Well, the good news is that Google Duo is now accessible on Chrome, Firefox, and Safari browsers.
At the moment, It seems that end users are having mixed experiences of using Google Duo for

Google Duo for Web
The Interface on the web is nothing much to look at. You have a list of a few recent contacts listed at the top. Below that, you have your full list of all contacts from your Google Contacts list. Note, the only contacts that will show up are the ones that have signed into Google Duo at some point. One bit of functionality that is included at launch, is the ability to have browser notifications for incoming calls. Excellent!
In order for you to use Google Duo, you first need to make sure your browser supports it. Seconds thing is that your Google user account is a standard non-G Suite account. Head on over to duo.google.com and you should be greeted with the new User Interface.
Google duo for web has not been officially announced yet. The official announcement and possibly more performance improvements and tweaks are most likely also on the way.