Convert WEBM files to MKV free in your browser — no signup, no install, and the file is never uploaded to a server.
Add your WEBM file
Drag the WEBM file onto the drop area above, or click it to pick a file from your device. You can add several files at once.
Confirm MKV as the output
MKV is already selected as the output format on this page. You can pick the resolution. Encoding is the slowest part, so smaller resolutions finish sooner.
Run the conversion
Press the convert button. Video is re-encoded frame by frame on your own machine, so a long clip can take several minutes. The tab has to stay open.
Download the MKV file
When it finishes, download the MKV file. Converting multiple files gives you the option to download them together as a ZIP.
An open video format created by Google for web streaming. It is royalty-free and compact, making it well suited to website background video.
An open-source video container able to hold unlimited subtitles, audio tracks, and chapters. It is favored for archiving high-quality video.
Yes. WEBM to MKV conversion is completely free with no signup, no watermark, and no daily limit on the free plan for ordinary use.
No. The conversion runs entirely inside your browser using WebAssembly, so the WEBM file never leaves your device. That is also why it works without an internet connection once the page has loaded.
No — MKV has no alpha channel, so transparent pixels are replaced with a solid background. If transparency matters, convert to PNG or WebP instead.
The free plan handles files up to 200MB. Because processing happens on your own device, very large files depend on your computer's memory rather than a server quota.
Video converter
What each file format is, what it is used for, and which formats it can be converted to.
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