Understand the shape problem
Vertical video is tall and narrow, while YouTube's main player and TVs are wide. Dropping a vertical clip straight in leaves black bars on both sides.
You cannot invent picture that was never filmed, so every fix is a trade-off between filling the space and keeping the subject visible.
Fill the sides with a background
Create a 16:9 project in your editor and place the vertical clip in the centre. Behind it, put a blurred, enlarged copy of the same clip, a brand colour, or a simple pattern.
Use the side space for helpful extras: chapter titles, step numbers, or a list of ingredients. This turns empty space into information.
Crop or combine clips
If the action happens in the middle band of the frame, crop a horizontal slice and enlarge it slightly. Check sharpness, since enlarging a phone clip too much makes it soft.
For comparisons, place two or three vertical clips side by side, such as before, during and after. This fills a wide frame naturally.
Shoot for both formats next time
If you know a video will be used in both shapes, film horizontally at high resolution and keep the subject in the centre third. You can then crop a vertical version and keep the wide one.
Many phones and editing apps also offer auto-reframe tools that follow the subject. Try them, but always review the result for awkward cuts.
Frequently asked questions
Is a blurred background unprofessional?
Not when done neatly; it is widely used. A branded background or extra on-screen information can look more polished.
Which resolution should I export for YouTube?
Exporting at the resolution of your source, often 1920x1080 for a 16:9 project, is a safe choice. Check YouTube's current recommended upload settings for details.