Convert MP4 to MKV
Some media players, TVs and editing tools want MKV. Convert here: the video is not re-made, only moved into a new file, on your own computer.
- Never uploaded
- No size limit
- No watermark
- Free
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Quick answer: To convert MP4 to MKV, drop the MP4 into the tool at the top of this page and press "Convert to MKV". The picture and sound are copied into the MKV as they are, so nothing is lost and the file stays the same size. It happens in your browser, so the video is never uploaded. It is free, with no sign-up and no watermark.
Updated
How it works
- Drop your videoThe file is read on your computer, never uploaded.
- ConvertThe picture and sound are copied into the new file as they are, so it takes seconds and loses nothing.
- Download the MKVOpens in VLC and most media players, TVs and editors.
Copied, not converted
The tool does not redo the picture or the sound. It moves them into a new MKV file, which took 1 second for our 20-second sample, and the file kept its size. For a comparison of the two file types, see MP4 vs MKV.
Do you need MKV?
If your player opens your MP4, there is nothing to gain. MKV helps when a program or device asks for it by name.
Measured, not promised
Measured on 21 Oct 2026 in Chrome on a 2019 Intel MacBook (an older laptop) with a 20-second 720p sample. Longer videos take longer; real files vary. More results.
Why your video never leaves your computer
Your video is processed by your own computer, inside this tab, and never uploaded. That is why there is no size limit and no watermark. How it works.
Questions
Does it lose quality?
No. The picture and sound are copied as they are.
Can I go back to MP4?
Yes: MKV to MP4.
Can I convert several files at once?
Yes. Choose or drop several files together. They are converted one after another with the same settings, and you can download each one or all of them in one ZIP.
Is my video uploaded?
No. It is processed inside this browser tab and saved straight back to your computer.