Convert WEBM to MKV
WEBM is great for web video, HTML5 players and screen recordings, but MKV is the better choice for movies with multiple audio tracks and subtitles. Convert WEBM to MKV in seconds, right in your browser.
- No upload — 100% private
- Fast, lossless when possible
- Free & unlimited
- Works on iPhone & Android
Keep this tab open — the conversion runs on your device, nothing is uploaded.
Add more files above to keep converting.
How to convert WEBM to MKV
- 1
Tap Choose files and select one or more WEBM files (or drag them in).
- 2
Check that MKV is selected. Use Advanced options for resolution, size or trimming.
- 3
Press Convert. Everything happens on your device — no upload, no waiting in a queue.
- 4
Your MKV downloads automatically. Converting several files? Grab them all as a ZIP.
WEBM vs MKV
WEBM and MKV can hold the same codecs, so in Smart mode the streams are copied — the conversion takes seconds and quality is identical to the original.
| WEBM | MKV | |
|---|---|---|
| Full name | WebM Video | Matroska Video |
| Type | Video | Video |
| Compression | Lossy | Lossy |
| Developed by | Matroska.org | |
| Introduced | 2010 | 2002 |
| Plays on iPhone | ◐ Partly / with an app | ✕ No |
| Plays on Android | ✓ Yes | ◐ Partly / with an app |
| Plays on Windows | ✓ Yes | ✓ Yes |
| Plays on Mac | ◐ Partly / with an app | ◐ Partly / with an app |
About WEBM and MKV
WEBM: WebM is Google's open video format using VP8/VP9 and Opus. It is built for the web and is what screen recorders and browsers produce.
MKV: MKV is a flexible open container that can hold unlimited video, audio and subtitle tracks. It is popular for movies and anime but isn't supported by iPhone or most TVs out of the box.
Frequently asked questions
How do I convert WEBM to MKV on my phone?
Will converting WEBM to MKV reduce quality?
Is this WEBM to MKV converter free?
Are my files uploaded to a server?
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