What is letterboxing in video?

Letterboxing meaning and the pillarbox twin

Letterboxing happens when a video is wider than the display. The player scales the picture to fit the width, which leaves empty bands above and below, and those bands are black. The video is not cropped, so nothing is lost. The cost is screen area.

This page covers the video term. The same word is used in other fields, such as games and web browsers, that it does not describe.

What happens when 16:9 meets 9:16

Do the arithmetic for a phone held upright. A 1920 by 1080 video fitted to the width of a 1080 by 1920 screen is scaled to 1080 by about 608 pixels. That leaves about 1,312 pixels of black, around two thirds of the screen height, split above and below. The picture shrinks to a thin strip in the middle.

This is why a 16:9 podcast uploaded as it is looks tiny on a phone. The fix is to reframe it instead: crop a 9:16 window out of the wide shot and follow the speaker. The aspect ratio glossary entry has the sums for other shapes.

What the platforms say about black bars

• YouTube: it advises not adding padding or black bars into the video itself, because they interfere with the player resizing to the video and device.
• Meta, on ads in Stories and Reels: on screens taller than 9:16 it may zoom the creative to fill the screen, which can crop areas outside the safe zone, or show it at 9:16 on a black background.
• Instagram: reels can be uploaded at an aspect ratio between 1.91:1 and 9:16.

Two of these are help pages about specific products and one is about ads, so use them as signals, not as one universal rule.

When bars are fine and when to reframe

• Reframe when the speaker is the point. A face fills the vertical frame better than a letterboxed strip.
• Keep the wide frame when it carries the content, such as a screen recording or a chart, and accept that the picture will be smaller.
• Never bake bars into the file to "fix" the ratio. YouTube advises against it, and you will get bars on top of the player's own padding.
• Check where captions land. Text placed inside a bar is easy to misjudge and may sit in the platform's interface zone; see safe zone.

Where KeyMo touches it

KeyMo exports clips as vertical 9:16 at 1080 by 1920, never 16:9, and does the reframe with automatic face tracking. Open the preview of any clip and check the framing before you export, since how a 16:9 source crops depends on where the speakers sit. See vertical video for the format itself.