Convert MP4 to WebM
Re-encode an MP4 as WebM with VP9 and Opus, for a smaller file on the web.
Drop a clip to start
Runs in your browser. Nothing is uploaded.
WebM with VP9 inside is meaningfully smaller than an H.264 MP4 at the same quality — commonly twenty to thirty per cent — and it is royalty-free, which is why it is the format the web itself leans on. For a video that will be served from a page rather than sent to a person, it is the better file.
The trade is reach. Every browser plays WebM and a great deal of other software does not: older phones, some smart TVs, plenty of editing tools and most things that predate it. If the file is going to a person rather than onto a page, MP4 remains the safer answer.
Both the audio and the video are converted, since a WebM cannot hold H.264 or AAC — VP9 and Opus are what goes in it. That means a full re-encode, so keep the quality high if the MP4 is your only copy.
Step by step
- 1Drop in your MP4 files.
- 2Pick a resolution and quality.
- 3Press Convert, then download.
Questions
Is WebM smaller than MP4?
Usually, at the same quality — VP9 is a more efficient codec than H.264, often by twenty to thirty per cent.
What plays WebM?
Every current browser. Outside the browser it is patchier: some TVs, older phones and various editors do not.
Why does the audio change too?
A WebM cannot contain AAC. The soundtrack becomes Opus, which is the codec that belongs in that container and is better besides.