webm → mp4
WebM to MP4, converted on your own machine
Drop a WebM file below and get an MP4 that plays in Premiere, iMovie, PowerPoint and every phone. No upload, no watermark, no account.
Files are processed on your device · nothing is uploaded, stored or logged
How it works
Pick your file. The browser reads it straight from disk. There is no upload progress bar, because there is no upload.
The encoder loads once. A WebAssembly build of FFmpeg, around 30 MB, downloads the first time you use the site and stays cached afterwards.
Your processor does the work. Everything happens in this tab, at roughly half of real time on a modern laptop.
Save the result. The finished file is assembled in memory and handed to your downloads folder.
Why WebM files cause trouble
WebM is built for web playback, and browsers handle it perfectly. Almost nothing else does. Windows Media Player, most TVs, PowerPoint, iMovie and older Premiere versions will either refuse the file or open it with no audio.
MP4 with H.264 video and AAC audio is the closest thing video has to a universal format. Every phone made in the last decade plays it, every editor imports it, and every platform accepts it on upload.
You will most often meet WebM after saving a video from a website, exporting from a browser-based screen recorder, or pulling a file out of a Chrome-based tool that defaulted to it.
What you give up in the conversion
Re-encoding always costs a little quality, because the video is decoded to raw frames and compressed again. It cannot be avoided: no MP4 container can hold VP9 video in a way normal players accept, so a straight copy is off the table. At the Balanced setting the loss is invisible in ordinary viewing.
If the converted file is larger than you need, run it through compress video.
Common questions
Is it really free?
Yes, with no file limit, no watermark and no account. Your machine does the encoding, so there is no server bill to pass on.
Do my files get uploaded?
No. Once the page has loaded you can disconnect from the internet and the converter still works — which is the simplest proof that nothing is being sent anywhere.
Why is it slower than HandBrake?
WebAssembly runs two to four times slower than a native install. Under a few minutes of footage you will barely notice. For a two-hour recording, install a desktop encoder instead.
What is the largest file it can handle?
Around 500 MB in practice. Browsers cap how much memory a single tab may claim, and very large files hit that ceiling before the conversion finishes.