Video textures and alpha transparency

Supported formats

WebM and HEVC/MOV formats are the only video formats that can be used on the web to display textures with alpha transparency.

WebM is supported in Chrome/Firefox/Edge/Samsung/Opera/Brave while HEVC/MOV is used on Safari (both desktop and mobile).

Selecting appropriate format

Use can use the following Puzzles snippet to select the video:

Converting WebM to HEVC

At the time of the writing, transparent videos are not supported in the stock libx265 encoder. Still you can use ffmpeg on Mac devices with hardware encoder called VideoToolbox to convert your videos:

ffmpeg -c:v libvpx-vp9 -i movie-webm.webm -c:v hevc_videotoolbox -alpha_quality 0.75 -vtag hvc1 movie-hevc.mov

You can install FFmpeg with Homebrew:

brew install ffmpeg

Converting video with chromakey (green screen) to WebM with alpha

To convert any video with chromakey (e.g MP4 which does not support alpha) to semi-transparent WebM:

ffmpeg -i movie-mp4.mp4 -vf "chromakey=0x2a9a2e:0.01:0.2" movie-webm.webm

See here for more info.