WebM to MP4 converter
Convert WebM files — common from screen recorders and browsers — to MP4 for editors, iPhones and social media.
The converter (32 MB) downloads once from this site when you press Convert.
ffmpeg log
Your video is processed on your device by ffmpeg.wasm, loaded from this site. It is never uploaded — open the Privacy check at the bottom of the page to watch.
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About WebM
WebM (VP8, VP9 or AV1 video) is an open format used by Chrome and many screen recorders. Some editing apps and Apple devices handle MP4 better, so converting with H.264 avoids compatibility problems.
Frequently asked questions
Is my video uploaded?
No. ffmpeg runs in your browser tab and reads the file from your device. The page’s security policy doesn’t allow it to send data anywhere; the Privacy check lists every request.
Why is the first conversion slow to start?
The converter engine (32 MB) downloads once from this site. After that it’s cached by your browser.
Which formats can it read?
Almost anything FFmpeg supports: MP4, MOV, WebM, MKV, AVI, FLV, 3GP and more, including HEVC iPhone videos.