One of the most notable premium features of YouTube is the ability to download virtually any video for offline playback. According to Android Police, YouTube briefly tested an extension of this feature that would use your account to sync downloads across multiple devices (like a phone and tablet). The new feature was apparently available in the stable and beta versions of the YouTube Android app, but Android Police was not able to get it to work.
In the settings menu, a “Cross-device offline settings” button would display a pop-up asking which device you would like to sync, along with a toggle that would “allow downloading to this device.” But testing this feature between two phones did not sync downloads between two Android phones that they tried it on. We’ve also checked the feature on a few different Android phones and haven’t seen it show up – whether it’s still available for limited testing or has been retired entirely remains to be seen.