How to use the video brightness and contrast editor
- Drop a video onto the box or click to choose one.
- Set Brightness, Contrast and Saturation. Each runs from 0% to 200%, where 100% means no change.
- Leave Output format on Same as the original, or choose MP4, WebM, MOV or MKV.
- Press Apply adjustments and wait for the progress bar.
- Compare the Before | after still, play the result, and download it. The file name ends in
-adjusted.
What it does and when to use it
Phone clips filmed indoors or at dusk often come out dim, and footage shot on hazy days or through windows can look flat and washed out. A small lift in brightness and contrast, and sometimes a touch more saturation, makes them much easier to watch. Turning saturation down to zero gives a black-and-white version for a mood piece or a consistent look across clips.
The same adjustment is used for the whole clip, so it works best when the lighting does not change much. If only part of the clip needs fixing, cut that part out with the video trimmer first. To adjust a still photo the same way, try the image brightness tool, and to make the result smaller to share, use the video compressor.
How it works
Each frame is decoded with Mediabunny in a background worker and drawn onto a canvas with the browser’s built-in brightness, contrast and saturate filters. If the browser does not support canvas filters in a worker, the tool does the same maths on every pixel itself:
- Brightness multiplies each colour value: value × brightness.
- Contrast stretches around mid-grey: (value − 0.5) × contrast + 0.5.
- Saturation mixes each colour with its grey, using the standard weights 0.213 red, 0.715 green and 0.072 blue.
Values are clipped to the 0–255 range and the frame is encoded again with WebCodecs. The audio is kept and nothing is uploaded.
Worked examples
These pixel values come from the tool’s own adjustment function.
| Pixel (R, G, B) | Settings | Result |
|---|---|---|
| 100, 150, 200 (a mid blue) | 120 / 110 / 100 | 119, 185, 251 |
| 20, 20, 20 (near black) | 120 / 110 / 100 | 14, 14, 14 |
| 200, 50, 50 (red) | 100 / 100 / 0 | 82, 82, 82 |
The second row shows why extra contrast can crush shadows: the dark grey gets darker even though brightness went up.
Limits and tips
- Re-encoding takes time and slightly lowers quality, so keep the original and make all your adjustments in one pass.
- Bright areas such as skies can turn pure white when brightness goes up, because values above 255 are clipped. Go up in small steps.
- AVI, WMV and FLV files are not read here; convert them first with the video converter.
Frequently asked questions
Can I preview the change before processing the whole video?
How do I make a video black and white?
Why do dark areas get darker when I add contrast?
Can it recover detail from a very dark clip?
Why does the video change if I press Apply without moving anything?
How do we know nothing is uploaded? Test it yourself on the privacy proof page.