WebM to MKV converter
Convert WebM files to MKV with TLS uploads and automatic deletion. Open container supporting virtually any codec combination.
Drop a WebM file, or click to browse
Converts to MKV · runs live, right now
How it works
Drop your file
Drag a WebM file in, or click to browse. No account needed to try it.
We convert it
Secure upload, converted to MKV in our ffmpeg pipeline.
Download the result
Grab your MKV file immediately, or find it later in your dashboard.
Why convert WebM to MKV?
Both WebM and MKV use lossy compression, so the conversion mainly changes compatibility, not quality. The main reason to convert WebM to MKV is compatibility: MKV plays back smoothly in browsers and on mobile without a codec pack, while WebM doesn't always. If you're sharing a file with someone else, sending it to a tool that expects a specific format, or archiving it for the long term, MKV is usually the safer target.
Format comparison
| WebM | MKV | |
|---|---|---|
| Extension | .webm | .mkv |
| MIME type | video/webm | video/x-matroska |
| Compression | lossy compression | lossy compression |
| Category | video | video |
Common reasons to convert WebM to MKV
- Meeting an upload size limit for a platform or an email attachment
- Playing back on a device or app that doesn't support WebM
- Standardizing on one format so every file behaves the same way in your workflow
Your file, handled carefully
Uploads use TLS in transit and AES-256 SSE-S3 at rest in production (when the production S3 credential gate is enabled), are processed in an isolated job, and deleted on the schedule you choose — as fast as immediately. We don't index, search, or share files between accounts. Read the full security model →
Frequently asked questions
Is converting WebM to MKV free?
Yes — the Free plan includes 50 conversions every month, including WebM to MKV. Paid plans raise that limit.
Will I lose quality converting WebM to MKV?
MKV is open container supporting virtually any codec combination. We use the highest-quality encoder settings by default so visual or data loss is minimized.
Do you keep a copy of my file?
Files are deleted automatically based on your plan's retention options. Free accounts can keep results for 1h or 24h; Pro and above add options such as delete-immediately and 7 days.
What is WebM?
Open, royalty-free video format built for the web.
Will my converted file have a watermark?
On the Free plan, MKV output includes a small "Converted with Convyx" mark. Pro ($9/mo) removes it, along with the 25 MB file size cap.
What happens if a conversion fails?
You get a clear error message and the job is marked failed in your history — we never silently drop a file. Retry is one click. Monthly quotas count attempts (including failures) because processing starts as soon as the job is created.