How to convert MP4 to WebM
- Drop your MP4 above — it stays on your computer.
- Set Convert to to WebM (VP9), and choose a target size if you want.
- Click Convert to WEBM and download the result.
Why use WebM?
WebM with VP9 is royalty-free and typically lands smaller than H.264 at the same quality, which is why it is common for background video and web embeds. Every modern browser plays it, though older devices and some editors do not.
Is WebM smaller than MP4?
Usually yes at the same visual quality, though it depends on the clip. VP9 encoding is also slower than H.264.
Will it play on an iPhone?
Recent iOS versions play VP9 in Safari, but MP4 is still the safer choice for sharing with people directly.
Does the audio convert too?
Yes — the soundtrack is re-encoded to Opus, which is the standard pairing for WebM.
Runs locally with mediabunny (WebCodecs), wavesurfer.js & jSquash. No upload, no account.