MP4 to WebM converter
Turn an MP4 into a royalty-free WebM file for the open web. The encode runs in this tab, so nothing is uploaded and there is no queue.
Drop an MP4 file here, or choose one
Converted on your device · nothing is uploaded · no size limit
- No upload — files stay on your device
- No signup and no watermark
- No file size limit
WebM exists so that video can be published without patent licensing attached to it. The container, the VP8 and VP9 video codecs inside it, and Opus audio are all open and royalty-free, which is why WebM turns up in browser recording APIs, in sticker and animation formats, and on sites that would rather not think about codec licensing at all.
This converter produces VP8 video with Opus audio. VP8 is the older of the two WebM video codecs and the one with the widest support: every browser that can play WebM at all can play VP8, going back well over a decade.
How to convert MP4 to WebM
- Choose your file. Drag an MP4 file onto the strip above, or click it to browse. The first file also loads the converter itself, which takes a few seconds.
- Wait for the bar to fill. Encoding runs on your own processor. A one-minute 1080p clip usually takes under a minute; keep the tab open while it works.
- Download the WebM. The finished file appears as a download button and saves straight to your device.
Why convert MP4 to WebM
No codec licensing to worry about
H.264 and AAC, the usual contents of an MP4, are covered by patent pools with licensing terms attached to encoding and distribution. VP8 and Opus are royalty-free, which removes the question entirely for anyone publishing video at scale.
Some platforms ask for WebM specifically
Animated stickers, certain browser extension formats and a number of upload endpoints accept WebM and nothing else. In those cases the format is not a preference, it is a requirement.
Transparency is possible
WebM can carry a real alpha channel, which MP4 cannot do in any broadly supported way. If you need a video overlay with a transparent background on a web page, WebM is the practical route.
Pair it with the MP4 as a fallback
Serve both from one HTML video element, WebM first, so browsers take whichever they understand. Safari in particular is far happier with the MP4.
What this conversion does and does not do
| Aspect | Result | Notes |
|---|---|---|
| Video codec | VP8, royalty-free | Widest WebM support |
| Audio codec | Opus at 128 kbps | Royalty-free, efficient at speech |
| File size | Similar to the source, sometimes larger | VP8 is not more efficient than H.264 |
| Encoding time | Slower than converting to MP4 | Expect a few minutes for long clips |
| Alpha channel | Supported by the format | Only if your source already has one |
Doing it yourself with ffmpeg
This command is deliberately different from the tool above. Run on your own machine, ffmpeg can use VP9, which compresses considerably better than the VP8 the browser version produces. If you want the smallest WebM you can get, this is how:
ffmpeg -i input.mp4 -c:v libvpx-vp9 -crf 33 -b:v 0 -row-mt 1 -c:a libopus -b:a 128k output.webmEvery flag is explained in the guide to the ffmpeg command.
Questions
Will the WebM be smaller than my MP4?
Usually not. VP8 is roughly comparable to H.264 in efficiency and can produce a slightly larger file at similar quality. The reason to choose WebM here is that it is royalty-free and required by some platforms, not that it saves space. VP9 is the codec that genuinely compresses better, and the command below produces it.
Why VP8 rather than VP9?
VP9 encoding is not stable in the WebAssembly build this site runs on, so offering it in the browser would mean handing you a tab that crashes rather than a file. VP8 encodes reliably here. If you want VP9, run the command below on your own machine, where it works properly.
Will the file play everywhere?
VP8 in WebM plays in Chrome, Edge, Firefox, Opera and Android, and in recent Safari. It does not play in the iOS Photos app, in QuickTime, or in most video editors, so keep your MP4 for anything outside a browser.
How long does it take?
Longer than converting to MP4. VP8 encoding is slower than H.264, and it runs on your own processor rather than a server. A one-minute 1080p clip typically takes a few minutes.
What quality setting is used?
Constrained quality at CRF 31 with a 1 Mbps ceiling, which suits web delivery at ordinary resolutions. Adjust the values in the command below if you need something specific.
Is my file uploaded?
No. The encoder runs in WebAssembly inside this page, and your video never leaves your device.