What can MkvDefaultTrackChanger do with MKV files?

Updated

MkvDefaultTrackChanger is a small open-source application that changes which audio and subtitle tracks are marked as default inside MKV video files. It is a good fit if you have MKV files where the wrong language or commentary track plays automatically, and you want a specific audio or subtitle track to be the one players select by default. It runs on Windows, Linux (GTK), and macOS, and it works on the file's track metadata rather than re-encoding the video, so it is fast.

What it actually changes

The tool edits the default-track flags stored in the MKV container. It does not convert, re-encode, or otherwise touch the video and audio streams themselves.

  • Default audio track — sets which audio track a player picks automatically when the file opens.
  • Default subtitle track — sets which subtitle track is selected by default.
  • No full-file processing — because it only rewrites the relevant metadata, it does not need to process the entire file, which is why it is described as fast.

A practical example: you rip or download an MKV that contains an English dub, the original Japanese audio, and multiple subtitle languages. The player keeps starting with the dub. You point the tool at the file, choose the track you want as default, and save — the next time the file opens, that track is selected.

Batch processing

The tool can process multiple MKV files at once. The important condition from the project description is that batch processing assumes the files share the same order of subtitle and audio tracks. If your files have tracks in a consistent order (common when they come from the same source or release group), you can apply the same default-track choice across all of them in one pass. If the track order varies between files, batch processing is not reliable and you would handle files individually.

Who it is for

Your situation Is it a fit?
MKV files play the wrong audio/subtitle track by default Yes
You have many MKV files with identical track order Yes — use batch processing
You want to re-encode or convert video No — it only changes default-track flags
Your files have inconsistent track order Partly — process them one at a time
You need a simple UI without extra options Yes — described as a simple UI with no bells and whistles

Getting it

The project offers downloads for Windows, Linux (GTK), and macOS, and the source is available on GitHub. The site does not state pricing, so check the download or repository page for current terms before relying on it being free.

Key limitations to keep in mind

  • It changes default flags only — it does not remove tracks, merge files, or fix playback problems unrelated to track selection.
  • Batch mode depends on consistent track order across files.
  • Because it edits metadata rather than the streams, the change is fast but also limited in scope to track defaults.

If your goal is simply "make this MKV open with the audio and subtitles I want," this tool targets exactly that task.