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document updated 1 year, 5 days ago, on Feb 28, 2023

If you download a video from TikTok and upload it to Facebook, Facebook will automatically crop part of the bottom of the video.

I believe it does this because TikTok videos have an aspect ratio of 9:16, while Facebook maxes out at a 4:5 aspect ratio for vertical videos that aren't shown in full-screen mode. (in full-screen mode, 9:16 videos work great)

If you want to do your own cropping before uploading, maybe use these dimensions: