Convert WebM to MP4
The browser-native format, translated for everything else — converted on your own hardware, never uploaded.
Drop your video or audio here
or
MP4, MOV, WebM, MKV, AVI, MP3, WAV and more — any size, no upload
🔒 Files never leave your device — everything runs in your browser.
WebM is what the web produces — browser screen recorders, many capture tools, and half the clips saved from the internet — and what almost nothing else accepts: iPhones look away, email previews fail, editing apps refuse. Because WebM uses genuinely different codecs (VP8/VP9) than MP4, this is a true conversion: ConvertUno decodes and re-encodes the video with your device's hardware acceleration, typically at or near the speed of simply playing the file.
Quality is preserved at a high-quality encoding target rather than a size target — if what you actually need is "under 25 MB for email", the WebM compressor page does conversion and size-fitting in one pass. As always: no upload, no size limit, no queue.
How it works
- Drop your file
Any common format, any size. Nothing is uploaded — the tool runs in your browser.
- Convert
Compatible files are repackaged instantly with zero quality loss; others are hardware-transcoded at high quality.
- Download
Your converted file is ready on your device — nothing to wait for, nothing to delete from a server.
Frequently asked questions
Why does WebM to MP4 take longer than my MKV conversion did?
MKV files usually contain MP4-compatible video that can be repackaged instantly. WebM's VP8/VP9 codecs genuinely differ from MP4's H.264, so every frame must be decoded and re-encoded — hardware acceleration keeps it near real-time speed.
Will the converted MP4 play on iPhone and in email?
Yes — the output is H.264 + AAC, the most compatible combination that exists: iPhones, Android, Windows, TVs, email clients, and every chat app open it natively.
Can I convert a WebM with no sound?
Of course — video-only WebM files (common for screen recordings) convert to video-only MP4s without complaint.
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.