Convert Video re-saves a clip as MP4 or MOV with H.264 video and AAC sound — the combination that plays on Windows, Macs, phones, smart TVs and in WhatsApp, and that almost every upload form accepts. Typical jobs: an iPhone MOV a Windows laptop will not play, a WebM screen recording, an MKV file from a camera.
The conversion runs in your browser with ffmpeg compiled to WebAssembly, so the video is never uploaded. The price of that privacy is speed: every frame is re-encoded on your own processor, so a long or 4K clip takes a while, and the first video job loads a roughly 30 MB video engine.
How to use
Add the video — MOV, MKV, AVI, WebM, MP4 and most other formats a phone or camera produces.
Pick MP4 (plays almost everywhere) or MOV (for Apple editing apps); leave it on MP4 if unsure.
Run it and keep the tab open while the frames are re-encoded.
Download the converted file.
FAQ
Can it convert to WebM, AVI or MKV?
No. Output is MP4 or MOV only, both with H.264 video and AAC audio. Those formats can go in, but they do not come out — and MP4 is the one nearly every device and site accepts anyway.
Is my video uploaded?
No. ffmpeg runs inside your browser tab and the new file is created there. Nothing is sent to a server, and no account is needed.
Will I lose quality?
The video is re-encoded, so it is not a bit-for-bit copy, but the default H.264 settings keep it visually close to the original. The file can come out larger or smaller than the source; to make it deliberately smaller, use Compress Video.
Why is it slow, and is there a size limit?
Every frame is decoded and encoded again on your own device, without help from the graphics card. There is no fixed limit, but very long or high-resolution videos can take many minutes and may exceed what a browser tab can hold in memory — phones reach that point sooner.