It has been announced on Google Product Forums that YouTube player for desktop now adapts automatically based on the aspect ratio of the video and the screen/browser size of the device you’re streaming the video on. The new update removes the black bars around vertical videos and overall provides a better video experience to the users.
A similar update was rolled out to Android and iOS devices a while back to overcome the unpleasant viewing experience while watching non-wide screen videos like vertical and square videos. Thus, the new update rolled out to the desktop player will ensure a uniform viewing experience on all your devices.
Community Manager Marissa also added that “For most newer videos in the standard HD aspect ratio, this update uses some of the screen’s extra white space, to enhance the video size, without impact to the video quality.”
Keep going to see the changes in pictures: