Many Google sites are already Progressive Web Apps (PWAs), allowing you to easily add them to your desktop or taskbar and use them in their own tableless windows like native applications. Following YouTube Music and YouTube TV, the regular YouTube site is now also one of these PWAs, as 9to5Google spotted.
The change has taken place in the last few days, and you can see that the option has reached you as soon as you see the signature plus button in the address bar of your browser that asks you to install the app when you click on it. After adding it to your applications, you will find YouTube in its own window, but no new features have been enabled thanks to PWA support, such as downloading for Premium users or so. The simple installation process is currently the only real benefit, although there is nothing stopping other changes from coming later.
Previously, you could turn the YouTube site (and actually any other) into a more windowed experience by clicking on the three-point overflow menu and navigating to More tools -> Create shortcut and tap the Open as window tick.
