Split screen

The layout exists because a vertical frame is tall and one talking head leaves most of it empty. Stacking a presenter over gameplay, a screen recording or a reaction target fills the space and gives the eye two things to follow, which is why it became the standard shape for commentary Shorts. Watch the safe areas. Captions, the handle, the description and the interaction buttons all sit over the bottom and right of the frame, so anything important placed there gets covered up. Editors build the two panels on a 1080 by 1920 canvas and keep faces and text inside the middle band.