The change even applies to regular 16:9 videos, taking advantage of the extra blank space to enlarge the picture. You might not rush to click the Theater Mode button quite so quickly as you did in the past.

This won't convince your friends to shoot videos in widescreen, no matter how much you might plead with them to mend their ways. YouTube was just swimming against the current by assuming that every clip was 16:9, however. If it didn't add support for different aspect ratios on all platforms, it risked losing out on creators and viewers who've grown up with Instagram and Snapchat.