What is vertical video?

An aspect ratio is a frame's width compared with its height. 9:16 is 9 units across for every 16 down: a phone screen held upright. 1080 × 1920 is the usual size at that shape, the pixels of a full HD video turned on its side. A regular YouTube video is the opposite, 16:9, and the free aspect ratio calculator works out either from any size.

The apps build their short video feeds around it. YouTube treats an upload of up to 3 minutes with a square or vertical aspect ratio as a Short, and says to use a wider ratio, such as 16:9, if you don't want a video to be one. TikTok's Creator Academy says you can post vertical video, or horizontal video in its Full Screen mode, and TikTok's web editor has a template that resizes a video to 9:16.

Why the apps favor it comes down to the screen. A 9:16 video fills all of it. A 16:9 video in the same feed, shrunk to the phone's width, fills about 32%: a strip across the middle, every face in it about a third the size a crop would show. When the next video is a swipe away, the one that fills the screen is the one that holds it. That's why every clip of a podcast, stream or interview gets made vertical before it's posted (see YouTube videos to Shorts), and why short-form video and vertical video are nearly the same thing.

Most long videos are 16:9. There are three ways to make one vertical, and they look nothing alike:

• Letterboxing (fit). The whole frame, shrunk to the screen's width, with bars or a blurred copy of itself above and below. Nothing is lost, but it fills about 32% of the screen, and YouTube's help center advises against adding padding or black bars to a video at all. It suits a slide, a chart or a wide scene where everything matters.
• Cropping. A 9:16 window cut out of the frame: from a 1920 × 1080 video, 608 × 1080 pixels, about 32% of its width, enlarged 1.8× to fill 1080 × 1920. It fills the screen, but a crop that never moves keeps whatever is in the middle, which on a two-person podcast is often the gap between the hosts.
• Reframing. The same window, moved as the video plays to whoever matters: the person talking, then the one who answers. By hand that's a cut and a new crop at every change; done for you it's auto reframe, which works by speaker tracking.

Choose by the footage: one person in the middle crops cleanly, two or more people need reframing, and a stream with a webcam in the corner is better stacked, the facecam over the game. To crop or fit one video yourself, the free vertical video converter does it in your browser; the steps for each editor are in how to convert a horizontal video to vertical.

• Posting 16:9 and expecting a Short. YouTube counts only square or vertical uploads as Shorts, and says to use 16:9 to keep a video out of them, so a wide video is a regular video, however short.
• Bars inside a 9:16 file. A wide video pasted onto a tall canvas is vertical on paper and wide on screen: the same 32% of the screen, with black or blur around it.
• Text and faces at the edges. The apps lay their buttons down the right and the account name and caption across the bottom. Keep captions and faces inside the safe zone, as TikTok's Creator Academy asks: centered, and not covered by buttons.
• A source too small for the crop. Past about 2× enlargement a picture looks soft. A crop of a 1080p video is enlarged 1.8×; of a 720p one, 2.7×. Clip from the best copy you have.