WebM to MKV - Online Video Converter
Convert WebM to MKV online. Private, client-side - no uploadrequired. Batch conversion, quality presets, codec control.
About WebM to MKV
Convert WebM to MKV. WebM pairs VP9 video with Opus audio and supports an alpha channel. MKV is an open container holding multiple video, audio, and subtitle tracks. Only the selected tracks carry over, so pick audio and subtitles first..
Why convert WebM to MKV?
- Smaller files with MKV lossy compression.
- Keep animation and transparency where supported.
- Private, no upload - runs in your browser.
WebM vs MKV
| Animation | Yes | Yes |
|---|---|---|
| Transparency | Yes | Yes |
| Compression | lossy | lossy |
| Typical use | WebM pairs VP9 video with Opus audio and supports an alpha channel. | MKV is an open container holding multiple video, audio, and subtitle tracks. |
When not to convert WebM to MKV
- Skip MKV for archival masters: lossy compression discards detail, so keep the WebM original.
- Keep a master copy: repeated exports stack small losses, so archive WebM before batch MKV shares.
Limits
Starting point: WebM - VP9 video with Opus audio and alpha support. Apple editors accept it unevenly; keep MP4 for editing round-trips. Only the selected tracks carry over, so pick audio and subtitles first. Encode MKV (H.264 / AAC) from WebM at a bitrate near the source, and confirm the audio track before converting.
How conversion works
Conversion runs entirely in your browser with FFmpeg WASM. Files never leave your device.