A test feature has become available on YouTube for users with a Premium subscription that allows you to scale videos,
Users can, without expanding the video to the fullscreen, stretch the video in such a way that small details in the frame become clearly visible. As noted, the function looks like it was specially made for viewing in portrait mode.
The feature is currently available to users.Android with Premium subscription. Testing will continue until September 1 - this time will be enough for developers to receive full feedback. But when the feature will become available to all users is unknown.