Aspect ratio

The ratio describes the shape of the frame, not its size. A 1920×1080 video and a 1280×720 video are both 16:9. The main ratios today are 16:9 (horizontal, standard for YouTube and TV), 9:16 (vertical, standard for TikTok, Instagram Reels and YouTube Shorts, typically 1080×1920), 1:1 (square) and 4:5 (a slightly tall format common in social feeds).

When a video doesn’t match the screen or the slot it’s played in, the player adds bars (letterboxing or pillarboxing) or crops it. Cropping a horizontal video to vertical usually cuts off text and important parts of the frame, which is why vertical content is best designed vertically from the start.

Short-form platforms are built around a full-screen vertical player. A 9:16 video fills the phone screen; a 16:9 video plays as a small band in the middle. For explainers that rely on text and diagrams, that difference decides whether anything is readable.

Composing for 9:16 also changes how you design: content stacks vertically, titles go in the upper part of the frame, and you have to leave room for the platform interface (see safe zone).

A comparison chart designed for 16:9 places five bars side by side. Squeezed into 9:16, each bar becomes a thin sliver and the labels become unreadable. Redesigned for vertical, the same chart becomes a stack of five horizontal bars, one per row, with labels on the left: same data, readable on a phone.