Many Google sites are already Progressive Web Apps (PWAs), which allows you to easily add them to your desktop or taskbar and use them in your own tabless windows, like native applications. Following YouTube Music and YouTube TV, the regular YouTube website is now also one of those PWAs, as 9to5Google noted.
The change has been implemented in the past few days, and you can tell that the option reached you as soon as you see the add signature button in the address bar of the browser that prompts you to install the app when you click on it. Once added to your applications, you will find YouTube in its own window, but there are no new features enabled thanks to PWA support, such as downloading for Premium users or the like. The simple installation process is the only real benefit for now, although there is nothing stopping further changes from being made later.
Previously, you could transform the YouTube website (and really any other one) into a more native window experience by clicking on the three-point drop-down menu and going to More tools -> Create shortcut and checking the Open as window selection box.
