How to convert MP4 to WebM
- Drop the .mp4 file.
- WebM is selected (VP9 where available, otherwise VP8).
- Pick a resolution and quality; 720p Medium is a good default for web backgrounds and demos.
- Click Convert, wait while it plays through once, and download.
Why WebM?
WebM is an open, royalty-free format designed for the web. VP9 video is supported by every modern browser, compresses well, and is a common choice for website background videos, HTML5 players, Discord and some game engines. Serving a WebM alongside an MP4 in a <video> element lets each browser pick the best one.
The conversion uses your browser's MediaRecorder encoder, which works in Chrome, Edge, Firefox and Safari. It runs in real time and re-encodes the video, so start from the best-quality source; converting an already compressed video again loses some detail. For a site background, also tick Remove audio and keep clips short, ideally under 15 seconds. Your video is processed on your device without uploading.
FAQ
Does WebM work on iPhone?
Safari on iOS 15+ plays VP9 WebM in most cases; MP4 is still the safest for Apple devices.
Is WebM smaller than MP4?
At the same quality, VP9 WebM is often smaller than H.264 MP4.
Can I keep transparency?
No. Videos recorded this way have no alpha channel.