Download free trialFree WebM to MP4 converter
Choose a .webm file and save it as an MP4 that plays in QuickTime, on an iPhone and on almost every site. Picture and sound that QuickTime does not play are re-encoded to H.264 and AAC, on this device.
The converter runs entirely in your browser - nothing is uploaded, and your video never leaves this device.
Where WebM files come from
Browser screen recorders and many web tools save WebM, because browsers can write it freely. The trouble starts afterwards: QuickTime Player will not open it, and some editors and sites will not take it. An MP4 with H.264 picture and AAC sound goes almost everywhere.
Questions about converting to MP4
- Is my video uploaded?
- No. The file is read and converted in your browser on this device. In some browsers the converted file waits in the browser's private storage until you press Save MP4, and it is deleted when you convert another file or come back to the page.
- Why does it re-encode the video?
- A WebM's VP8, VP9 or AV1 picture and Opus sound are not what QuickTime and many players expect inside an MP4, so the converter turns them into H.264 and AAC rather than make an MP4 that will not play.
- Will the quality change?
- Re-encoding always changes the picture a little, because it is compressed again. Converting once from the original keeps that to a minimum.
- How long does it take?
- It depends on the length and size of the video and on the device doing the work, because the re-encoding happens on your computer rather than on a server. A progress bar shows how far it has got.
- Which browsers does it work in?
- It needs a browser that can encode H.264 and AAC, such as Safari 26 or later or Chrome. Where a browser cannot, the converter says so before it starts.
Recording and exporting on a Mac
Rooster records your screen and camera on your Mac, lets you edit the video by editing its transcript, and exports an MP4 - H.264, or a smaller HEVC file - rendered on your Mac with nothing uploaded. See how exporting works, or you can try Rooster free.
This converter is built on Mediabunny 1.61.6, by Vanilagy and contributors, used unmodified under the Mozilla Public License 2.0.