Convert an MP4 video to WebM locally via re-encoding - smaller, royalty-free and ideal for your own website. No upload.
Running locally on your device ...
Running locally on your device ...
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Your files never left your device
No. Everything runs in your browser - your file never leaves your device. How this is verifiable
MP4 (with H.264/AAC) is the universal standard, but that is not always the best trade-off for your own website: H.264 is a patent-encumbered, licensed format, while WebM (VP8/VP9/AV1 + Opus) is open and royalty-free - a popular reason self-hosted or privacy-conscious sites embed WebM instead of or alongside MP4.
MP4's H.264/AAC content never fits WebM's lossless copy set - this conversion is therefore always a real re-encode, via your browser's native VP9 or AV1 encoder (WebCodecs). At comparable quality, WebM often ends up smaller than the original MP4, which matters especially for streaming and page load time on a website.
Everything runs locally in the browser via your device's native video encoders. Your video is not uploaded - handy when, say, you are preparing a private explainer video for your own self-hosted website.
| Input formats | MP4, M4V |
|---|---|
| Output format | WebM |
| Batch processing | No |
| Processing | Locally in your browser (WebCodecs) |
| File upload | None |
Limitations: Always a real re-encode with minimal but measurable quality loss and unchanged resolution (for a different resolution/quality, use the sibling tool "Compress video"). One file per run, ~1 GB limit (4 GB/tab in the browser).
No, the entire conversion happens locally in your browser.
WebM is open and royalty-free (no H.264 patent question) and often produces a smaller file at comparable quality.
Minimally, as with any re-encode - the chosen resolution stays unchanged.
In any current browser, yes; on some older devices or in classic editing software, no - MP4 remains the safer choice there.
Yes, use the sibling tool "Convert WebM to MP4".
WebM to MP4 · MP4 to MKV · MP4 to MOV · MKV to MP4 · GIF to WebM