Pick your source frame and the platform ratio you're cropping to. See the crop box and the classic title-safe / action-safe zones live, with exact pixel offsets — so you know before you reframe whether a face, a caption, or a logo is about to get clipped.
Action-safe (90% of the frame, a 5% margin on every side) and title-safe (80%, a 10% margin) are the classic SMPTE broadcast conventions for keeping essential action and on-screen text away from overscan clipping. They're still a solid rule of thumb for keeping key text and graphics clear of platform UI (captions, buttons, profile chips) on vertical social video — but every app's UI is different and changes over time, so treat this as a planning guide, not a guarantee, and check the live preview in whatever app you're actually posting to.