Google has turned it Google photos site into a PWA with the latest update. This is not the first time that Google has launched a PWA version of it's apps it has already done this with Google maps.
This new Photos PWA was first spotted by Intel developer Kenneth Rohde Christiansen. With me testing the PWA the app doesn't seem to work offline. However, you can enable desktop notifications to receive real-time alerts from Google Photos. This PWA supports Chromebook, Windows and Android.
As of Chrome 67, Google has enabled PWAs by default. This means you can easily add Google Photos to your desktop after visiting the Photos site. If its not enabled in your browser then you can enable it with the helo of this chrome flag chrome://flags/#enable-desktop-pwas.
If PWA's are enabled in your Desktop browser then it will automatically prompt you to install the PWA when you open the Google Photos site. If it is not prompted then you can manually add it to desktop by clicking on the three vertical dots in your browser followed by more tools and then selecting on add to desktop installs the PWA on your Desktop.
For an Android device if you are prompted to install it then its straight forward but incase you don't get the prompt to install the PWA then click on the three dots and click on add to home screen.
Google is looking forward to create an ecosystem of PWA version of it's apps so that users can use them everywhere without any issue.
Even we do have a PWA the you can install on your android device and also on your Desktop. Follow the steps mentioned above to install our PWA.