OneTaskBy Tim King · Updated
Remove Black Bars
Detect and Crop Letterbox or Pillarbox Bars From a Video Automatically
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How the Remove Black Bars works
Remove black bars from a video without measuring anything. The tool scans the clip, finds the letterbox bars above and below or the pillarbox bars at the sides, and crops them off. Choose a detection level, press Render and download. It all happens in your browser.
Black bars appear whenever a picture is placed in a frame of a different shape. A widescreen film in a 16:9 file gets bars top and bottom. A vertical phone clip posted as landscape gets bars on both sides. A screen recording of a video player picks up the player's own bars. The bars waste pixels, shrink the picture on every screen and look sloppy when the clip is reposted.
Letterbox, pillarbox and windowbox
| Bars | Name | Common cause |
|---|---|---|
| Top and bottom | Letterbox | 2.39:1 or 1.85:1 film in a 16:9 frame |
| Left and right | Pillarbox | 4:3 TV or 9:16 phone video in a 16:9 frame |
| All four sides | Windowbox | A letterboxed film inside a 4:3 broadcast |
A 2.39:1 film in a 1920 × 1080 frame carries about 140 pixels of black above and below, a quarter of the frame. A 9:16 phone clip pillarboxed into 16:9 uses less than a third of the frame width.
How Remove Black Bars detects the bars
The tool takes 10 frames spread evenly through the clip and works on copies up to 480 pixels wide. For every row and column it records the brightest pixel seen in any of those frames. A row only counts as part of a bar if it stayed dark in all 10 samples, so a dark scene or a fade to black does not fool it. It then counts dark rows in from each edge, up to half the frame, and converts the counts back to full-size pixels.
The video is then rendered with just the picture area, scaled to even dimensions as video encoders require, along with the original sound.
Choosing the detection level
Brightness here is luma on a 0–255 scale. A pixel is treated as bar if its brightest value across the samples is at or below the limit.
| Level | Limit | Use it for |
|---|---|---|
| Strict | 16 | Clean digital bars that are true black |
| Normal | 28 | Most files, including slightly noisy bars |
| Loose | 40 | Dark-grey bars from old transfers or screen recordings |
Video "black" is usually 16 rather than 0, because broadcast video reserves the lowest levels. Compression noise lifts it a little further, which is why Normal sits at 28.
Tips and pitfalls
Night scenes at the edge of frame. If a dark shot runs right to the frame edge in every sample, Loose can trim into the picture. Start with Normal and only go Loose if bars are left behind.
Bars that change size. Some films switch aspect ratio for certain scenes, such as IMAX sequences. The tool keeps only rows that are dark in every sample, so it crops to the largest picture and some scenes keep thin bars.
Logos in the bars. A channel logo or subtitle sitting in the bar makes that row bright, so the bar is not removed on that side. Crop that clip by hand with the video cropper instead.
How to read the result
The stats list how many pixels were removed from each side, the picture size before and after, and the file size. If nothing was found, the tool says so instead of rendering an unchanged copy.
FAQ
What causes black bars on a video?
Black bars appear when the shape of the picture does not match the shape of the frame. Widescreen films get bars above and below in a 16:9 file, and vertical phone videos get bars at the sides when they are placed in a landscape frame.
Why did it say no black bars were found?
Every edge row and column was brighter than the limit in at least one of the 10 sample frames. Try Loose if the bars are dark grey. If a logo or caption sits inside the bar, use the video cropper and set the crop yourself instead.
Will removing the bars stretch the picture?
No. Only the black area is cut away and the picture keeps its true shape. A letterboxed film comes out wider than 16:9, which is correct. To fit a set frame shape, use the cropper or padder after.
Is the video uploaded to detect the bars?
No. The sample frames are analysed and the cropped video is recorded in your own browser. Nothing is sent to a server, so the tool also works on private footage and after you go offline.
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