MP4 to MKV Converter - free, no upload, in your browser

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Why this runs on your computer

There is no upload: The work happens in this tab. Your file never travels, so there is no copy of it anywhere but your own disk.
Nothing to delete later: Sites that upload promise to delete your file afterwards. That promise only matters because the file was theirs to hold.
It works with the Wi-Fi off: The honest test. Turn off your connection and the tools keep working, because everything they need is already here.

Drop your file hereto convert it

Nothing is uploaded - the tools run right here

Applies to every loaded image

Look Strength 100% Brightness Contrast Saturation Vibrance Vignette

Max width

Format Shape

Colours 6 Detail 1 Smooth curves

Shape Size Across Down Border

Text Where

100%

Questions

Why convert MP4 to MKV?

MP4 is the format everything plays, and the safe answer when you are not sure. MKV is the archivist's container: it holds anything, but few devices play it directly. Converting is how you move a file from the first situation to the second.

What will the MKV file contain?

H.264 video and AAC sound, though MKV holds almost anything, so most sources are repackaged as they are.

Is the picture re-encoded?

Usually not. An MP4 file normally carries H.264 video, which MKV can hold as it is, so the picture is copied across untouched and the conversion takes seconds. Only a file holding something else is re-encoded.

Is the sound kept?

Yes. The audio track comes across with the picture - copied when MKV can hold it as it is, converted when it cannot.

How long does it take?

Repackaging takes seconds. A full re-encode runs in this tab on one processor core, so a long HD video takes a while - but there is no upload or download to wait for.

Convert MP4 to MKV without uploading it

How to convert MP4 to MKV

Why this one stays private

Questions

The same tool, other formats