Convert WEBM to MKV online in seconds — free, with no sign-up. MKV is lossy and ideal for archiving films with multiple tracks; converted to MP4 for compatibility. Your files are encrypted and deleted automatically after 24 hours.
WEBM
WebM — A royalty-free web video format (VP8/VP9) that's smaller than H.264 at equal quality.
MKV
Matroska Video — A flexible container that holds multiple audio, video and subtitle tracks.
How to convert WEBM to MKV
- 1Upload your WEBM file
Click “Choose a file” or drag and drop your WEBM file onto the page — no sign-up or email needed.
- 2Convert to MKV
MKV is already selected as the output. Open Options to fine-tune quality if you like, then click Convert.
- 3Download your MKV file
Your MKV file is ready in seconds — click Download to save it. Files are automatically deleted after 24 hours.
WEBM vs MKV
| WEBM | MKV | |
|---|---|---|
| Full name | WebM | Matroska Video |
| Type | Video | Video |
| Compression | Lossy | Lossy |
| Best for | efficient web video in Chrome, Firefox and Edge | archiving films with multiple tracks; converted to MP4 for compatibility |
Frequently asked questions
Does converting WEBM to MKV lose quality?
Both WEBM and MKV use compression, so re-encoding discards a little more data. For a single conversion the change is virtually invisible; just avoid repeatedly re-converting the same file.
What's the difference between WEBM and MKV?
WebM (WEBM) is lossy and best for efficient web video in Chrome, Firefox and Edge. Matroska Video (MKV) is lossy and best for archiving films with multiple tracks; converted to MP4 for compatibility. Convert WEBM to MKV when you need a video for archiving films with multiple tracks.
Is the WEBM to MKV converter free?
Yes — converting WEBM to MKV is completely free. There's no watermark, no sign-up and no email required, and you can convert as many files as you like.
Are my WEBM files private and secure?
Yes. Your uploads are encrypted in transit, processed privately, and automatically deleted within 24 hours. We never share, sell or look at your files.
Can I convert WEBM to MKV on iPhone, Android, Mac or Windows?
Yes. The converter runs entirely in your browser, so it works on any device — iPhone, iPad, Android, Mac, Windows or Linux — with nothing to download or install.
How long does it take to convert WEBM to MKV?
Most files convert in a few seconds. Larger files take a little longer, and your upload speed is usually the limiting factor. There's no queue and no waiting for an email.
What else can I convert WEBM files to?
Besides MKV, you can convert WEBM to AAC, AVI, FLAC, FLV, GIF, JPG and more — see the full list of WEBM conversions below.
Other conversions
Last updated July 2026