A bash script that converts green screen video into transparent video files for use on the web.

It produces two output files from a single input:

• .webm (VP9 with alpha) for Chrome, Firefox, and Edge
• .mov (HEVC with alpha) for Safari

• ffmpeg with libvpx-vp9 and hevc_videotoolbox (macOS) support
• Python 3 (for auto-detecting the green screen color)

On macOS with Homebrew:

brew install ffmpeg python

./make-video-transparent.sh [options] <input>

# Auto-detect green screen color from the video
./make-video-transparent.sh video.mp4

# Specify the green color manually
./make-video-transparent.sh -c 97c64c video.mp4

# Tweak similarity and blend for cleaner edges
./make-video-transparent.sh -s 0.15 -b 0.08 video.mp4

# Output to a specific directory
./make-video-transparent.sh -o ~/Desktop/output video.mp4

<video autoplay loop muted playsinline>
  <source src="video.mov" type="video/mp4; codecs=hvc1">
  <source src="video.webm" type="video/webm">
</video>

Then change the background with CSS:

video {
  background-color: rebeccapurple;
}

See the live demo at https://zeke.github.io/make-video-transparent — it shows a transparent video with a color picker to dynamically change the background.

The demo/ directory contains the source for this page. To test locally with your own videos, generate transparent videos with the script, drop them in demo/, and open demo/index.html in a browser.

1. Auto-detects the green screen color by sampling a 200x200 pixel patch from the top-left corner of the first frame
2. Applies ffmpeg's colorkey filter to replace matching pixels with transparency
3. Encodes to WebM (VP9) and MOV (HEVC) with alpha channels

The color auto-detection assumes the top-left corner of the video is green screen. If your subject covers that area, pass the color manually with -c.