Glossary
What is pillarboxing?
By the KeyMo team · Updated
Pillarboxing is the black bars at the left and right of a video that is narrower than the screen playing it. It happens when a 4:3 or vertical picture is shown on a wide display without being stretched or cropped. The bars are empty space, not part of the video.
Pillarboxing definition
A screen has a shape, and a video has a shape. When the video is narrower than the screen, the player keeps the picture's proportions and fills the leftover width with black bars, like pillars on either side. The word gets used in film, television and games, and it means the same thing in all of them.
| Term | Bars are at | Happens when |
|---|---|---|
| Pillarboxing | Left and right | A narrow picture (4:3, 9:16) plays on a wide screen |
| Letterboxing | Top and bottom | A wide picture plays on a taller or squarer screen |
| Windowboxing | All four sides | A picture is smaller than the screen both ways |
Pillarboxing in film and in games
In film and television the classic case is old 4:3 footage on a widescreen set. A 4:3 picture is 1.33 times as wide as it is tall, and a 16:9 screen is 1.78 times. The 4:3 picture fills the full height, uses about 75% of the width and leaves about 12.5% black on each side.
In games, pillarboxing appears when a game is built for one shape and the monitor is another. A 4:3 game on a widescreen monitor gets bars at the sides if the player chooses to keep the original shape, and stretching is the other option.
Why vertical clips get pillarboxed
A vertical 9:16 clip is the narrowest common shape. Play one on a 16:9 desktop player and it is shown at full height with large bars at the sides. At 1080 pixels tall, the picture is about 608 pixels wide on a 1920-pixel-wide screen, which is roughly 32% of the width. The remaining 68% is bars.
YouTube's help page says 9:16 videos on computer browsers may be shown with padding (white by default, dark gray in Dark theme). Meta says that on screens taller than 9:16, a creative may be zoomed to fill the screen or shown at 9:16 on a black background, which on a taller phone puts the bars at top and bottom.
Mistakes and how to avoid them
- Exporting a wide video with bars added above and below to "make it vertical". That is letterboxing inside a vertical frame, and it wastes most of the screen.
- Stretching a narrow video to remove side bars. Faces turn wide and the picture looks wrong.
- Cropping a 16:9 frame to 9:16 without checking where the speaker sits. The crop can cut a face in half.
The usual fix is to reframe, not pad. See auto-reframe and aspect ratio.
Where KeyMo touches it
KeyMo exports every clip as vertical 9:16, 1080x1920, never 16:9. Face-tracking reframes the wide source to follow the speaker, so no bars are baked into the file. If you see bars on the sides, they come from the player on a wide screen.
Sources: YouTube Help: Video resolution & aspect ratios (checked 11 October 2026); Meta Business Help: About text overlays and the safe zone for ads in Stories and Reels (checked 11 October 2026).