WebM to MP4 Converter

Convert WebM to MP4 so it plays outside a browser. This one is a real re-encode rather than a repackaging job — here is why.

  • 100% private
  • No sign-up
  • No watermark
  • Unlimited files
Drop a WebM file hereor tap to browse · one file at a time · nothing is uploaded

    On the default setting this usually finishes in seconds, because the picture and sound are copied across unchanged rather than re-encoded. Everything runs on your own device — the file is never uploaded.

    This conversion is genuinely slow, and that is unavoidable

    Most conversions between video containers are quick, because the same video can simply be moved into a different wrapper. WebM is the exception. It holds VP8, VP9 or AV1 video with Vorbis or Opus audio, and none of those play reliably in an MP4 on consumer hardware.

    So the picture has to be decoded and encoded again as H.264. That takes minutes rather than seconds and costs a little quality. Any tool claiming an instant WebM to MP4 conversion is either re-encoding and not saying so, or producing an MP4 that your television will refuse to play.

    The trap of a technically valid file

    It is entirely possible to put VP9 video inside an MP4 container. The specification allows it, and the file will be accepted by software that happens to support VP9. It will also fail on most televisions, older phones, editing software and upload forms — the exact places you needed an MP4 for.

    That is worth knowing because it is a real failure mode of other converters: the file arrives quickly, it has the right extension, and it still does not play. This tool checks what is inside the file rather than trusting the container, and re-encodes when it must.

    Where WebM files come from

    WebM was designed for the web, and browsers produce it constantly: screen recordings made with browser-based tools, video downloaded from sites that stream VP9, and anything captured through the MediaRecorder API all tend to arrive as WebM.

    It is an efficient format — VP9 and AV1 both beat H.264 at the same bitrate — which is why the converted MP4 is often larger than the WebM it came from. That is the cost of a format everything can play.

    Frequently asked questions

    Are my files uploaded to a server?

    No. The conversion runs inside your browser using your device's own processor. Your files are never transmitted anywhere, which is why the tool works even if you disconnect from the internet after the page loads.

    Why does this take minutes when MOV to MP4 takes seconds?

    MOV usually contains H.264, which MP4 accepts as-is, so the streams are copied. WebM contains VP9 or AV1, which cannot be copied into an MP4 that plays reliably, so every frame must be decoded and re-encoded.

    Will the MP4 be bigger than the WebM?

    Often, yes. VP9 and AV1 are more efficient than H.264, so matching their quality takes more data. You are trading file size for the ability to play the file anywhere.

    Will the quality drop?

    Slightly. Re-encoding is lossy, and the source was already compressed. At the default setting the difference is hard to see on normal viewing, but it is not lossless the way a container change is.

    Is there a file limit or a paywall?

    There is no account, no watermark, and no upload cap. Because your device does the work, the only practical limit is your available memory. The site is funded by ads, not subscriptions.

    Further reading

    Related tools