Add your files
Drop one MP4 or two hundred. Batch conversion is not a paid feature here.
Convert MP4 to MKV
Multiple audio tracks, chapters or proper subtitle files need to live inside one file, and MP4 handles all three badly.
Runs on your deviceFreeNo sign-upBatch supported
Where the streams already fit the target container this is a lossless remux, which is close to instant. Otherwise it re-encodes, which in a browser is slow — keep it under a few hundred MB and send long videos to the cloud engine.
Waiting for files/Engine: on-device/Network requests made: 0
What actually changes
MP4 and MKV are not the same picture in two wrappers.
The video and audio streams are copied unchanged into a Matroska container. No re-encoding happens, so quality is identical and the operation is limited by disk speed rather than CPU.
Worth knowing first
MKV plays everywhere that runs VLC and almost nowhere else by default. Smart TVs, browsers, iOS and most consoles will not open it, so this is a conversion for a home media server, not for sharing.
Questions
MP4 to MKV, answered
Does this reduce quality?
No. Nothing is re-encoded. It is a container change.
Why choose MKV at all?
It handles chapters, unlimited tracks, and subtitle formats like ASS that MP4 cannot represent.
How to convert MP4 to MKV
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Choose your settings
Matroska Video is lossless, so nothing is thrown away in the conversion.
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Download
Instant, because the file never went anywhere. Nothing expires, since nothing was stored.