Convert WebM to MP4
WebM is the open video format Google started in 2010, and it's what browsers record: screen recorders and webcam pages in Chrome and Firefox often save WebM. An MP4 with H.264 plays on far more phones, editors and upload forms.
Your file never leaves this device. Everything runs in your browser.
How it works
- Drop your video.
- Pick the format you need. The tool says which parts it copies and which it re-encodes.
- Press Convert and download the new file.
Questions
Why does WebM to MP4 usually re-encode?
A WebM almost always holds VP8, VP9 or AV1 video and Vorbis or Opus sound, which an MP4 that plays everywhere doesn't use, so both are re-encoded: it takes a while and works on videos up to 15 minutes. Some Chrome screen recordings put H.264 inside a WebM; their picture is copied as it is, in seconds.
What about a WebM with a transparent background?
H.264 can't be transparent, so a WebM with a transparent background, as some stickers and overlays have, loses it in an MP4. Keep those as WebM.
Which formats can I convert to?
MP4 and MOV with H.264 video and AAC sound, and WebM with VP9 video and Opus sound: the formats a browser can write. AVI, FLV and WMV aren't offered, because no browser can make them.
Does converting lose quality?
Not when the video is copied: a MOV or MKV holding H.264 becomes an MP4 without its picture being touched. When the codec has to change, the video is re-encoded at high quality, and like any re-encode it isn't bit-for-bit the original.
Is there a length limit?
Files up to 2 GB. A conversion that copies the video has no length limit; one that re-encodes it takes videos up to 15 minutes.
What happens to subtitles and extra audio tracks?
The new file gets the main video and the main sound. Subtitle tracks and extra languages, which an MKV often carries, are left out.
Does my video get uploaded?
No. It's converted in your browser, on your device.
Which browsers does it work in?
Current Chrome, Edge, Safari and Firefox. Re-encoding to MP4 or MOV needs a browser that can encode H.264, which Chrome, Edge and Safari can. Making a WebM needs VP9 and Opus encoders, which Chrome and Edge have. If yours can't, the tool says so before it starts.