Convert WebM to MKV
Runs locally in your browser via a WebAssembly build of ffmpeg. Your file is never sent to a server.
- Choose a .webm file from your device.
- Click convert to MKV.
- Download the result.
Maximum file size: 100 MB. The first conversion loads a ~30 MB converter engine, once per visit. Nothing is uploaded - conversion runs on your device.
WebM vs MKV
WebM is an open, web-native format that produces smaller files at a similar quality, popular for embedding on websites. MKV is an open container that can hold multiple audio/subtitle tracks, common for downloaded or archived video.
Frequently asked
Why convert WebM to MKV?
WebM is an open, web-native format that produces smaller files at a similar quality, popular for embedding on websites. MKV is an open container that can hold multiple audio/subtitle tracks, common for downloaded or archived video. Converting between them is common when a file made for one use needs to work for the other.
Does this upload my file anywhere?
No. Conversion runs entirely on your device using a WebAssembly build of ffmpeg - the file never reaches a server.
Is there a file size limit?
Yes, 100 MB per file, to keep conversion reliable inside the browser.
Koldflux exports every clip in the right format automatically - no manual conversion step.
Automate this in Koldflux