Merge MKV Files - join MKV videos free, no upload

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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 video hereto join them

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

Can MKV files be merged without re-encoding?

Yes, when they match - files from the same camera, recorder or export usually do. They are joined as they are and saved as MKV, which is fast and loses nothing. Files that differ are re-encoded so they fit together.

Can a browser really open MKV files?

Not on its own - Chrome, Firefox and Safari only play some MKV files, depending on what is inside, which is why most in-browser converters turn MKV away or quietly upload it. This page brings its own decoder: FFmpeg, compiled to WebAssembly and fetched from this site (10 MB, once) the first time you convert. After that the MKV file is read entirely in this tab.

Do the clips need to match?

No. Clips with the same codec and size - from the same camera, say - are joined without re-encoding, which is fast and loses nothing. Mixed clips are brought to the first clip's size and frame rate, letterboxed rather than stretched.

Can I mix formats?

Yes - an AVI, a WMV and an MP4 can go into one file. Pick the format to save it in.

Merge MKV files into one, without uploading them

How to merge MKV files

Why this one stays private

Questions

The same tool, other formats