WebM
An open web video format that uses VP8, VP9 or AV1 video with Opus or Vorbis audio.
- Type
- video
- Best for
- video on websites
No account · no upload · no watermark
Convert WEBM to MKV. Completely free.
Drop your WEBM and get an MKV back, right here in this tab. Your own computer does the work, so nothing gets uploaded, and there's no paid version.
WEBM to MKV converter
Matroska Video
An open container that can hold almost any codec plus multiple audio and subtitle tracks.
- Type
- video
- Best for
- archiving films with several tracks
What to expect
If the video and audio inside are already something MKV can hold, they're copied across with no quality loss, which takes seconds. Otherwise they're re-encoded, on your graphics hardware where possible and with FFmpeg in the tab where not.
How to convert WEBM to MKV
- Drop your WEBM on this page, or choose it from your device.
- MKV is already selected. Adjust quality, size or trim if you want to, and each option shows the size it will produce.
- Press Convert, watch it work, then download the result.
Questions
Is this WEBM to MKV converter really free?
Yes, completely. Every tool and every format is free, and there's no paid version, account, watermark or daily limit.
Do my files get uploaded?
No. Your browser does the work on your own device, so your files stay with you. Closing the tab clears them from memory.
Can I convert several files at once?
Yes. Drop as many as you like, and the results can be downloaded together as a ZIP.
Does it work on a phone?
Yes, in a current mobile browser. Large files are limited by how much memory your device can spare.
What should I know about WEBM to MKV?
If the video and audio inside are already something MKV can hold, they're copied across with no quality loss, which takes seconds. Otherwise they're re-encoded, on your graphics hardware where possible and with FFmpeg in the tab where not.
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Ready to convert your WEBM?
- Completely free
- Nothing uploaded
- No account
- No watermark