Updated June 2026 · runs 100% in your browser
WebM to MP4
Convert WebM videos to MP4 on your device. No upload, no sign-up, no limits.
Drop WebM files here
or click to choose
🔒 Processed on your device · 0 bytes uploaded
First file loads the converter engine (~25 MB) — cached after that.
How it works
ConvertCabin loads a local copy of FFmpeg in this browser tab and converts on your device — nothing is uploaded. The first file downloads the engine (~25 MB), then it's cached.
It stays free, unlimited and private, and works offline once loaded.
About WebM to MP4
WebM is a web format; MP4 is better for editors, phones and messaging apps.
Frequently asked questions
How do I use WebM to MP4?
Drop WebM files and download the MP4s.
Is my file uploaded?
No. It is converted on your device by a local copy of FFmpeg and never uploaded.
What is a WEBM file?
WebM is an open, royalty-free video format built for the web. It produces small files that stream well in browsers, though it has less support in desktop video software than MP4.
What is an MP4 file?
MP4 is the most universally compatible video container. It typically holds H.264 video with AAC audio, plays on virtually every device, and balances good quality with reasonable file size.