Convert MP4 to MKV Online
Turn MP4 files into MKV directly in your browser using ConverterUp. There is no upload, no waiting in a queue, and no account required — your files stay on your device while WebAssembly does the work locally. Adjust quality and dimensions where supported, then download the result. The output keeps the visual fidelity you'd expect from a desktop app while running entirely in the browser tab.
Convert MP4 to MKV nowHow to convert MP4 to MKV
Open the converter
Click the button to open the MP4 to MKV tool. It loads instantly — no install, no signup.
Drop your MP4 file
Drag your MP4 file into the upload area or click to browse. The file stays in your browser memory only.
Download MKV
The conversion runs locally and finishes in seconds. Click download to save the MKV file to your device.
Frequently asked questions
Is the MP4 to MKV conversion really free?
Yes. ConverterUp is fully free, with no signup, no watermarks, and no daily quota for the MP4 to MKV converter. We support the project through unobtrusive ads.
Are my MP4 files uploaded to a server?
No. Conversion runs in your browser using WebAssembly. The MP4 bytes never leave your device, and we have no upload endpoint at all.
What is the maximum file size?
For MP4 input, the soft cap is 50 MB for images and 500 MB for video. Practical performance depends on your device's RAM.
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Ready to convert MP4 to MKV?
Open the tool, drop your file, and download the result. No upload, no signup, no watermarks.
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