Compress WebM files
The screen-recording format, tamed: shrink WebM files on your own device and get an MP4 that opens anywhere you send it.
Drop your video here
or
MP4, MOV, WebM, MKV, AVI and more — any size, no upload
🔒 Files never leave your device — everything runs in your browser.
WebM is what browsers, OBS setups, and screen-recording tools love to produce — and what half the apps you share to refuse to open. Long recordings also balloon: an hour of screen capture at a generous bitrate swallows gigabytes for content that is mostly static pixels.
That static-heavy content is precisely where re-encoding shines. Screen recordings compress spectacularly well — often to a tenth of their size with no visible difference — and ConvertUno outputs H.264 MP4, so the file you share opens in the email clients, chat apps, and office tools that greet raw WebM with a shrug. All of it on your own machine, with a guaranteed output size.
How it works
- Drop your file
Any common format, any size. Nothing is uploaded — the tool runs in your browser.
- Pick your target
Use the presets above — this page's defaults are tuned for compress webm — or type any size.
- Download
Your converted file is ready on your device — nothing to wait for, nothing to delete from a server.
Frequently asked questions
Why won't people open my WebM files?
WebM plays beautifully in browsers but poorly outside them — many email previews, office suites, older phones, and Apple apps do not open it. Converting to MP4 during compression solves the compatibility and the size problem in one pass.
How well do screen recordings compress?
Better than almost any other footage. Static screens with occasional movement carry little information per second, so a tutorial or demo recording often shrinks 5–10x with no visible loss. Fast-scrolling content or embedded video compresses less dramatically.
Can I keep the output as WebM instead of MP4?
Not yet — the compressor outputs MP4 for universal playback, which is what most sharing situations need. A WebM output option is on the roadmap alongside the full converter suite.
Is my file uploaded to a server?
No. ConvertUno runs entirely in your browser on your own device. Your file never leaves your computer or phone — there is no upload at all.
Is it really free, with no watermark?
Yes. Processing happens on your device, so serving you costs us almost nothing — no watermark, no account, no file-size limit, no daily quota.