Why does MakeMKV generate similar files?

MakeMKV is today by far the best software when it comes to ripping Blu-Ray discs, but understanding the what the output files are can be a little confusing as some of them may be very similar. In certain cases MakeMKV generates similar output files with basically the same file name.

Region based file exports

In one example we can see that MakeMKV generates two files:

filename_t00.mkv  42,4 GB
filename_t01.mkv  38,8 GB

So what is the difference between these two files? If we use MediInfo to check the metadata of the video files we can see that they contain different streams (or tracks in layman terms).

You can have a look at the diff compare here: https://www.diffchecker.com/SreezWms So we can see that t00 contains tracks meant for a European or “western” viewers since it contains languages such as Spanish, French and German. The other file, t01 contains Japanese language and subtitles. The video streams should be exactly the same though.