Turn a tweet into a YouTube Short

YouTube treats any video under 60 seconds with a vertical aspect ratio as a Short, so hitting 9:16 exactly is what keeps it out of the regular player with black bars either side. Shorts also autoplay muted and loop, which suits a silent tweet animation.

Paste a link above to see the preview here.

This page renders at 1080 by 1920 with a longer hold than the Reels preset, because Shorts viewers arrive mid-loop and need the card on screen long enough to read from any entry point.

Questions

What makes YouTube treat my upload as a Short?
A vertical or square aspect ratio and a length under 60 seconds. A 1080 by 1920 export satisfies both.
Do Shorts need sound?
No. They autoplay muted, so a silent tweet animation is normal. Add music in the YouTube editor afterwards if you want it.
Why is this preset longer than the others?
Shorts loop and viewers join partway through, so the readable card needs to stay on screen long enough to be caught from any point in the loop.