Video Converter 100% In-Browser Nothing Uploaded

MP4 to WebM

Convert MP4 to WebM for smaller, web-friendly video — free, with no account and no limits. The conversion runs entirely in your browser, so your video never leaves your device.

Why convert MP4 to WebM?

MP4 (H.264) is the universal capture and sharing format, but it's rarely the smallest option for the open web. WebM (VP9/Opus) typically delivers noticeably smaller files at similar quality, which means faster page loads and less bandwidth for self-hosted HTML5 video.

It's also fully open and royalty-free, and supported by every major modern browser via the native <video> element — ideal when you control the markup and want lean delivery.

Common Use Cases

  • Self-hosted HTML5 background and hero video
  • Smaller clips for faster-loading pages
  • Open, royalty-free delivery on the web
  • Replacing autoplaying GIFs with real video
  • Docs, wikis, and product pages
  • Anywhere bandwidth and load time matter
Is it really free?
Yes — fully free with no account and no limits. The conversion runs in your browser using your own device, so there's nothing for us to meter.
Does my video get uploaded?
No. Everything happens locally via your browser's built-in video engine (WebCodecs). Your file never leaves your device and nothing is sent to a server.
Can I convert several files at once?
Yes. Add multiple MP4s and they're converted one after another, each downloaded automatically as a .webm file.
Will the quality change?
WebM is a re-encode, not a lossless rewrap, so it's recompressed. At sensible settings the difference is hard to spot, and you usually get a smaller file at similar visual quality.
Which browsers are supported?
Any modern browser with WebCodecs — current Chrome, Edge, Firefox, and Safari. If a conversion isn't supported on your browser, you'll get a clear message instead of a silent failure.
Is there a file size or length limit?
There's no fixed cap, but because it runs on your device, very large files use more memory and take longer. Desktop handles big files best.

How it works

1

Add your MP4s

Drop in one or more MP4 files. They stay on your device — nothing uploads.

2

Convert in-browser

Your browser re-encodes each file to WebM with a live progress readout.

3

Download the WebM

Each converted file downloads automatically, ready for your site.

Also available

Resize & compress video →

Use Magic Flow to also resize or shrink while converting

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