9:16: fill the screen.
Vertical framing suits phone-first, full-screen viewing. Keep the main action near the center so it remains clear when an app places captions or controls around the edges.
16:9: let the scene breathe.
Landscape gives architecture, scenery and wider compositions space. It is useful when the environment contributes as much as the subject to the story.
1:1: keep the focus.
Square framing is compact and balanced. It can work for close subjects and feed posts, especially when you want the viewer’s eye to stay on one central idea.
Check before sharing.
Preview your finished clip in the context where you plan to use it. Crop, interface overlays and captions can change how it feels. Keep the original download so you can prepare a version for another format later.