Video conversion
Convert WebM to MKV
Updated Jul 2026
WebM is built for playing directly inside web browsers, while MKV is a container made to hold video for playback on TVs, desktop players, and other devices. Converting WebM to MKV usually just repackages the same video and audio into a new wrapper, so there's no quality loss. Do it on your own computer and the file never has to leave your machine.
- Extension
- .webm
- Type
- Video
- Typically
- Web video
- Compression
- Lossy
- Extension
- .mkv
- Type
- Video
- Typically
- High-quality video containers
Convert WebM to MKV on your own computer. Nothing uploads.
How to convert WebM to MKV
- Open Morphjet and drag in the WebM file, or a whole folder of them, to convert several at once.
- Choose MKV as the output format.
- Convert. Morphjet repackages the video into MKV and writes it next to the original, and nothing leaves your machine.
WebM vs MKV: what actually changes
| WebM | MKV | |
|---|---|---|
| File size | Compact, encoded for streaming | Same size, since the video is repackaged rather than re-encoded |
| Quality | High, tuned for web delivery | Unchanged, the same video and audio streams in a new container |
| Compatibility | Plays in browsers and web apps, less consistent elsewhere | Opens in most desktop media players, smart TVs, and standalone players |
| Subtitles and multiple tracks | Limited support | Built to hold multiple audio tracks, subtitles, and chapters |
| Typical use | Embedding video on a webpage | Storing, archiving, or playing video outside a browser |
When to convert, and when not to
Convert WebM to MKV when you've downloaded or recorded web video and want to play it in a desktop media player, a smart TV, or an app that doesn't recognize WebM, or when you want a container that can also carry subtitles and extra audio tracks.
Keep the file as WebM if it only needs to live on a website or play back in a browser, since that's exactly what the format was built for.
Why not just use an online converter?
Converting video online usually means uploading the whole clip to someone else's server and waiting for it to come back, hoping it actually gets deleted afterward. Video files can be large and sometimes carry identifying details in filenames or embedded metadata. Converting WebM to MKV on your own computer means the file is repackaged locally and never has to travel over the internet.
Questions
Does converting WebM to MKV lose quality?
No. MKV is a container, not a codec, so converting from WebM to MKV usually just repackages the same video and audio streams into a new wrapper without re-encoding. The picture and sound stay exactly as they were.
Will an MKV file play in more places than WebM?
Generally yes. WebM is built for web browsers, while MKV is widely supported by desktop media players, smart TVs, and standalone devices that may not recognize WebM at all.
Does MKV keep subtitles and multiple audio tracks?
Yes, that's one reason people convert to MKV. It's built to hold multiple audio tracks, subtitle tracks, and chapter markers in a single file, more than WebM typically carries.
Can I convert WebM to MKV without uploading it anywhere?
Yes. A desktop app like Morphjet repackages the file on your own computer, so it never has to leave your machine or pass through anyone else's server.
Morphjet converts WebM, MKV, and 1,800+ other formats, all on your machine. Launching this July.