YouTube Music is adding offline downloads to its web app, thereby broadening its selection. This capability was previously limited to mobile devices—iOS and Android, in particular. It is now being implemented on the web platform to improve user experience.
Google has reportedly been testing offline downloads for its music streaming service on the web app, according to a recent report by 9to5Google. Although the functionality has been tested for some time, there has just been a noticeable larger deployment. Users may now download music for offline listening, as indicated by a notification that appears next to the Library tab.
It's possible that not everyone can see the feature yet, but some users have apparently noticed a notice next to their Library tab that says, "New! To listen to music offline, download it."