MP4 to MKV Converter
Convert MP4 to MKV for flexible Matroska containers. Free, private, up to 100 MB.
- No signup
- Private
- Fast
Super Fast
Convert in seconds on desktop and mobile.
100% Private
Files never leave your device.
Secure
Browser-side processing only.
MKV output
Matroska container for flexible media storage.
Why use this tool?
MKV supports multiple tracks and is popular for archiving and media libraries.
How to convert MP4 to MKV
Step 1: Upload your MP4 video
Choose a MP4 video from your device or drag it into the upload area. Files up to 100 MB are supported.
Step 2: Convert in your browser
We convert the video to MKV locally using FFmpeg in your browser — nothing is uploaded to our servers.
Step 3: Download your MKV
Preview the result and download the converted file with one click.
Supported formats
- Input: MP4 (.mp4) up to 100 MB
- Output: MKV
Frequently asked questions
Is this MP4 to MKV converter free?
Yes. Convert MP4 to MKV online for free — no account, no watermark, and no limits on how many files you convert.
Are my files uploaded to your servers?
No. Conversion runs entirely in your browser with FFmpeg WebAssembly. Your files never leave your device.
What is the maximum file size?
You can convert MP4 videos up to 100 MB per file. Longer or higher-resolution clips may be slow or fail on low-memory devices — try shorter clips if conversion times out.
Why does the first conversion take longer?
The first run downloads the FFmpeg engine into your browser (one time per session). Later conversions on the same page are faster.