WebM to MP4 converter
Convert a downloaded WebM into an MP4 that plays in editors, on phones, and in apps that refuse WebM. The conversion runs in your browser, so your file stays on your device.
Your file stays on your device. It is never uploaded.
How to
Convert WebM to MP4
Add the .webm file
Drop the downloaded WebM onto the tool, or choose it from your device.
Optionally cap the size
Keep the original size for best quality, or cap the resolution for a smaller file.
Convert and download
You get an H.264 MP4 that plays almost everywhere.
Questions
Frequently asked
Why will my WebM not play?
WebM is well supported in browsers but not everywhere. Many editors, some phones, and some messaging apps do not accept it. Converting to MP4 with H.264 fixes almost all of these cases.
Is the WebM uploaded?
No. DivXpress converts the file inside your browser on your device, with no upload.
Will the audio come across?
Yes. The audio is re-encoded to AAC and kept in the resulting MP4.
Is anything lost in the conversion?
Converting re-encodes the video, so there is some loss, but at the default quality it is hard to notice. Pick the highest quality setting to stay as close to the source as possible.
Sources
Where the format claims come from
WebM and MP4 carry different codecs, and that difference is the entire reason this conversion exists. It is documented in public.
- The WebM Project. The definition of WebM itself, and the VP9 with Opus pairing it carries.
- FFmpeg H.264 encoding guide. The CRF scale, what each value costs you, and why a quality target beats a bitrate target.
- MDN Web Docs: Media. Mozilla's reference for which containers and codecs browsers will actually play.