webm → mp4
WebM to MP4, without the file going anywhere
WebM plays beautifully in browsers and badly almost everywhere else. This turns it into the one format that has never given anyone trouble.
Processed on your own hardware · never transmitted, never stored
What happens when you drop a file in
The file stays put. Your browser opens it the same way an image viewer would. There is no transfer, which is why there is no upload bar to watch.
An encoder arrives once. The first job on this site pulls down a compiled build of FFmpeg, roughly 30 MB. It is kept afterwards, so every job after the first starts immediately.
Your own hardware does the job. The work happens in this tab, on your processor. A laptop from the last few years handles short clips in well under real time.
The result lands in Downloads. Assembled in memory and handed straight to your browser. Close the tab and every trace of it is gone.
Why WebM keeps causing problems
The format was designed for the web specifically, and browsers handle it perfectly. Very little else does. Presentation software, older editing suites, most televisions and a surprising number of upload forms will either refuse it outright or open it with no sound.
MP4 carrying H.264 video and AAC audio is as close to universal as video gets. Every phone made in the past decade plays it, every editor imports it, and no platform rejects it.
You usually meet WebM by accident: saving a video from a web page, exporting from a browser-based screen recorder, or receiving a file from someone whose tool defaulted to it without telling them.
This one cannot avoid re-encoding
Unlike a MOV or an MKV, a WebM cannot simply be repackaged. It carries VP8 or VP9 video, and no MP4 that ordinary players accept can hold either — so the picture genuinely has to be decoded and compressed again. At the middle setting that loss stays invisible in normal viewing, but it is real, and no tool can avoid it.
Common questions
Is there really no cost?
None. No file limit, no watermark, no account. Your machine does the work, so there is no bill to pass along.
Does the file get sent to a server?
No. Once the page has loaded you can disconnect from the internet entirely and the conversion still finishes.
Why is it slower than a desktop program?
Browser-based encoding runs two to four times slower than installed software. Under a few minutes of footage you will barely notice; for a feature-length file, install something.
What size can it handle?
Around 500 MB in practice. A browser tab is capped on how much memory it may claim, and very large files reach that ceiling mid-job.