Today I have discovered a cool feature in YouTube that allows you to fix aspect ratios of uploaded videos without having to re-upload the video. You can enter “yt:” formatting tags in the YouTube tag field of any video. With these “yt:” formatting tags, you can remove black borders, fix incorrect aspect ratios, and even default the YouTube quality to HQ.
The commands used for these respectively are:
See the following video for examples on how these work.
I used this technique on Eric and Cynthia’s wedding video, which originally had an incorrect 4:3 aspect ratio, and now the video plays back correctly at 16:9.