WEBM to MKV Converter
Processing entirely on your device — large files may take a moment.
MKV is ideal for archiving movies with multiple audio tracks and subtitles intact. If your files are still in WEBM format, this page is the shortcut: WebM is Google’s royalty-free web video format (VP8/VP9 + Opus). It is small, streams beautifully, and every modern browser plays it natively.
This converter runs entirely in your browser using WebAssembly — your files never leave your device, nothing is uploaded, and there are no watermarks, sign-ups or queues. Drop in several files at once to convert them as a batch.
How to convert WEBM to MKV
- 1
Select your files
Drag & drop your WEBM files onto the area above, or click to browse. You can add multiple files at once for batch conversion.
- 2
Convert instantly
Click "Convert to MKV". The conversion runs entirely inside your browser using WebAssembly — no upload, no queue, no waiting.
- 3
Download results
Download each converted MKV file individually, or grab everything at once as a ZIP archive.
Frequently asked questions
Is this WEBM to MKV converter really free?
Yes — completely free, with no sign-up, no watermark and no daily conversion limits. The site is supported by advertising.
Are my files uploaded to a server?
No. The conversion runs entirely inside your browser using WebAssembly, so your files never leave your device — that is what makes it instant and private.
Does it work on Windows, Mac, iPhone and Android?
Yes. Anything with a modern browser works: Windows, macOS, Linux, Android and iOS. No software installation is required.
Is there a file size limit for WEBM to MKV?
The only limit is your device's memory, since nothing is uploaded. Files up to a few hundred megabytes work fine on a modern desktop browser; very large files simply take a little longer.