Google Duo is now available via the web on desktops
Google Duo is no longer exclusive to the App Store and Google Play Store, with a web client launching for the service today.
People with Google accounts can now access a web based version of the Google Duo voice and video calling service via https://duo.google.com/ , even if they have never used the service before.
The web version of Google Duo is completely compatible and synchronized with the Android and iOS versions. All of your Duo contacts are available, and the web version supports regular widescreen and phone-based narrow video frames.
The service is being actively rolled out, so if you cannot use the web version of Google Duo yet, check back at https://duo.google.com/ every few hours to see if you can access it.