If your Short has black bars, you uploaded the wrong size. YouTube Shorts are 1080 by 1920. Vertical. That's it.
The classic mistake is repurposing horizontal footage by uploading it as-is. YouTube will show it. It'll just look awful: huge empty space, tiny subject, sad engagement. Either crop to vertical and track the subject, or better, shoot vertical in the first place. Planning beats fixing, every single time. And the same 1080 by 1920 export works for TikTok and Reels, so one file covers all three.
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The youtube shorts dimensions and length limit have shifted over time, the length cap especially, so verify the current number before you plan around it. Thumbnails for Shorts are newer and worth using. Pick a frame that actually represents the video instead of letting the algorithm pick a mid-blink moment. Hitting the youtube shorts thumbnail size on your phone is quick with a mobile app to resize photos for every platform. Crop a still, check the pixel count, done.
Discovery works differently here than long-form. Shorts have their own feed, their own shelf, their own audience behavior. People swipe fast and decide in about a second. Your first frame is your thumbnail, your title, and your pitch all at once. So open with the interesting part, not the intro animation. Safe zones apply too. The Shorts interface covers the right edge and bottom with buttons and titles. Center your subject, keep text in the middle band, and you'll look like you know what you're doing even if this is upload number one.
Here's what nobody says: most sizing mistakes happen at export, not filming. A video spec formatter app free to use catches the wrong aspect ratio before you upload, which beats deleting a flopped Short and reposting. Current dimensions and limits are tracked at easyimagevideo.com. And if you want one upload turned into correctly formatted versions for Shorts, TikTok, and Reels, that's exactly what our service does.