How to use the webm to mp4 converter
- 1
Select your file
Drag a file onto the box or click to browse. It stays on your device, nothing is uploaded.
- 2
Click Convert to MP4
FFmpeg runs in your browser. The first run also downloads the FFmpeg core, so it takes a little longer.
- 3
Download the MP4
When it finishes, download the MP4 file. Re-run with another file any time.
Why WebM to MP4 needs re-encoding
WebM almost always uses VP8 or VP9 video with Opus or Vorbis audio, which MP4 players do not widely support. Unlike MOV or MKV, a simple remux usually won't work, so the converter re-encodes to H.264 video and AAC audio. That takes longer than a remux, especially for long clips, because the browser is doing the encoding.
Common WebM sources
WebM is what you get from many screen recorders, browser-based capture tools, and videos saved from the web. Converting to MP4 makes those clips editable in standard software and uploadable to platforms that reject WebM, without handing the footage to a remote server.
Frequently asked questions
Is the WebM to MP4 converter free?
Yes, it is free with no ads, sign-up, or watermark, and it runs entirely in your browser.
Why is WebM to MP4 slower than other conversions?
WebM uses VP8/VP9, which MP4 can't simply repackage, so the video is re-encoded to H.264 in your browser. Re-encoding is more CPU-intensive than a remux.
Is my WebM file uploaded?
No. Conversion runs locally with FFmpeg WebAssembly; the file never leaves your device.
Does converting WebM to MP4 reduce quality?
Re-encoding is lossy by nature, but the converter uses a high-quality H.264 setting (CRF 23) so the difference is usually hard to notice.