Filming & Production
Aspect ratio
Also called: frame ratio
Widescreen video is 16:9, vertical formats such as Shorts, Reels and TikTok are 9:16, and square is 1:1. The ratio is separate from resolution, so 1920x1080 and 3840x2160 are both 16:9.
Trouble starts when a file arrives in the wrong ratio. A player will letterbox or pillarbox to protect the image, which shrinks it, and an automatic crop will happily take the top of a head off. Shooting 16:9 with the vertical crop in mind, or framing wide enough that a 9:16 pull still works, saves the reframe later. Anything with text near an edge needs checking in every ratio it will ship in.