If you upload rather or less than 16:9 frame video then Youtube will add a black bar to adjust the size. So try to upload to according to that size. Well, some software export video according to this ratio and some software. I use Camtasia9 for screen recording video and there I do not have to adjust the size. But in above premier pro, I have to adjust size.
If you try to with Adobe then after editing then go to File>Export>Media>Format>H.264. This is the best format setting for Youtube video Adobe premier pro. Below the video, I also described how to fix black bar problem. If you have any question then just comment below.
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