Aspect ratio: the root of the problem
Aspect ratio is the relationship between the width and height of an image, written as two numbers such as 16:9. A 16:9 frame is 16 units wide for every 9 units tall. Most TVs, monitors, and laptop screens use this shape.
Other shapes are common too. Older TV footage is 4:3, which is closer to a square. Upright phone video is usually 9:16. Feature films are often wider than 16:9, for example around 2.39:1.
When a frame of one shape is shown inside a frame of another shape without cropping or distortion, part of the outer frame stays empty. Those empty areas are the black bars.
Video dimensions versus display dimensions
Video dimensions are the width and height of the file in pixels, such as 1920 × 1080. Display dimensions are the size of the area where the video is shown: a player window, a TV screen, an embedded player on a web page.
These two things are independent. A 1440 × 1080 file (4:3) can be played in a 1920 × 1080 window (16:9). The file has no bars in it, but the player adds them on the left and right to fill its own window. The reverse also happens: a 1920 × 1080 file can contain a 4:3 picture with black columns saved on both sides.
The three kinds of black bars
Letterboxing: bars at the top and bottom
Letterboxing means a wide picture is shown inside a narrower frame, with black bands above and below it. The classic example is a widescreen movie on a standard display. The full width of the picture is kept, and the unused height is filled with black.
Pillarboxing: bars on the left and right
Pillarboxing is the sideways version. A narrower picture is centered inside a wider frame, and black columns fill the sides. This is what you see when 4:3 footage plays on a 16:9 screen, or when an upright phone clip is shown in a horizontal player.
Windowboxing: bars on all four sides
Windowboxing happens when letterboxing and pillarboxing occur together, leaving a black frame around the entire picture. It usually means the video was formatted twice: a widescreen clip was letterboxed into a 4:3 file, and that file was later placed in a 16:9 project. The visible picture ends up small.
Embedded borders versus player-added bars
This distinction decides everything that follows. Embedded borders are actual black pixels stored in the video frames. They travel with the file and appear in different players, devices, and editors. The file's pixel dimensions include them.
Player-added bars do not exist in the file. The player, the TV, or the web page draws them to fill its own display area, and they change or vanish on another device. YouTube's help documentation, for instance, explains that its player adapts to the shape of each video and may add its own padding on some devices, and it advises against adding black bars directly to the video.
If the borders are in the file, you can remove embedded black borders with automatic border detection. If they come from the player, there is nothing in the file to remove, and editing the video will not help.
Diagnostic table: what you see and what it means
| What you see | Likely cause | Are the bars inside the file? | Recommended fix |
|---|---|---|---|
| Bars at the top and bottom | Wide video on a narrower display or embedded letterboxing | Sometimes | Remove embedded borders or keep the original aspect ratio |
| Bars on the left and right | 4:3 video on a 16:9 display | Sometimes | Crop embedded borders, redesign the canvas, or keep pillarboxing |
| Bars around all sides | Video was exported with borders and then placed in another frame | Usually | Crop the embedded border area |
| Bars only in one player | Player/display mismatch | Usually not | Change player or display settings |
| Bars around a vertical clip | Vertical video placed on a horizontal canvas | Usually | Export as 9:16 or intentionally use a designed background |
How to check your own video in six steps
- Open the source file in another player. Use the original file, not a streamed or shared copy. A second player gives you a second opinion.
- Check whether the bars appear in every player. Resize the player window too. Player-added bars grow and shrink as the window changes shape. Embedded borders keep the same proportion to the picture.
- Inspect the actual video dimensions. Look at the file properties or media info. If the file says 1920 × 1080 but the visible picture is clearly narrower or shorter than 16:9, the difference is made of border pixels.
- Scrub through dark and bright scenes. In a dark scene, the picture can blend into the bars and hide where the real edge is. A bright scene shows the boundary clearly.
- Determine whether the borders are uniform and embedded. Uniform means solid black, the same thickness from the first frame to the last. Borders that shift, fade, or contain logos or patterns are a different case.
- Choose the action. Pick automatic removal, manual crop, resize, or no change, based on what you found. The next section explains each option.
Choosing the right fix
Automatic removal for uniform embedded borders
When the borders are solid black, even, and constant throughout the video, automatic border cropping is the quickest route. The Deus.Video tool analyzes the video frame, detects the uniform black border area, and crops those pixels. No manual cropping is required, and the visible image is not stretched.
The result has a new resolution, because the frame is now smaller than before. A 1920 × 1080 file with pillarbox columns might become 1440 × 1080. When the borders are detected correctly, none of the actual picture is removed.
Have black borders embedded in the video file? Use the Remove Black Bars tool from Deus.Video to detect and crop them automatically without stretching the visible image.
Manual crop for irregular cases
Some videos are harder to read automatically. Very dark footage can look like border area. Decorative frames, borders of different thickness on each side, and borders that change during the video are also difficult. In these cases, use Crop Video and set the visible area yourself.
Resize when the target shape is the real issue
If you need a specific output shape, such as a vertical version of a horizontal clip, removing borders alone will not get you there. Resize Video changes the output dimensions or canvas. Our guide to crop vs. resize vs. zoom vs. remove black bars explains how these operations differ.
No change at all
If the bars come from the player, or were added on purpose, leave the file alone.
Practical examples
A digitized family tape. The file is 1920 × 1080, but the picture is a 4:3 rectangle in the middle. The columns are in every player and never change. This is embedded pillarboxing, and automatic border removal will return a 4:3 file.
A movie clip that looks fine on a laptop but has bars on a phone. The file has no borders. The phone screen is a different shape from the laptop screen, and each player fills the difference. Nothing needs fixing.
A phone clip edited in a horizontal project. The export is 16:9 with big black sides. Removing the borders gives you back a vertical clip. For future projects, set the canvas to 9:16 before exporting.
Conclusion
Black bars are the visible result of a shape mismatch. The first question is always whether they live in the file or only in the player. Bars from the player need no editing. Uniform borders saved in the file can be detected and cropped automatically, which changes the resolution but leaves the picture itself untouched. Anything irregular calls for a manual crop or a fresh export with the right canvas.
Frequently asked questions
Why does my video have black bars on YouTube but not on my computer?
The file probably has no bars in it. A web player or TV app has its own display area and fills unused space itself. If the bars change when you switch devices or go full screen, they are added at playback and cannot be removed by editing the file.
Do black bars make the file bigger?
Solid black areas compress very efficiently, so they add little to the file size. The real cost is wasted resolution. A 1920 × 1080 file with a windowboxed picture may contain far fewer useful pixels than its dimensions suggest.
Why do the bars seem to disappear in dark scenes?
They are still there. When the picture itself is nearly black, the boundary between image and border becomes hard to see. This is also why very dark videos are harder for automatic detection and may need a manual crop.
Should I add black bars myself before uploading a video?
Usually not. Modern players adjust to the shape of the video. Bars saved into the file stop the player from doing that and can lead to windowboxing on other screens. YouTube's own guidance recommends uploading without added padding.
Sources
- YouTube Help, "Video resolution & aspect ratios" – player adapts to video shape, may add padding, advises against adding black bars to the file: https://support.google.com/youtube/answer/6375112 (checked September 17, 2026)
- Dictionary.com, "letterbox" – definition of the letterbox technique: https://dictionary.com/browse/letterbox
- Wikipedia, "Pillarbox" – definition and causes of pillarboxing: https://en.wikipedia.org/wiki/Pillarbox
- Wikipedia, "Windowbox (filmmaking)" – letterbox and pillarbox occurring together, double formatting example: https://en.wikipedia.org/wiki/Windowbox_(filmmaking)
