Software update: MKVToolNix 40.0.0

Shortly after the release of MKVToolNix version 39, Moritz Bunkus released another successor. With this open source program, matroska files can be viewed, edited and converted. For example, soundtracks and subtitles can be added, removed or set as default. MKVToolNix is ​​a collection of separate command line tools, but a graphical user interface is also included. Downloads are available for Windows, various Linux distributions and macOS. The changelog for this release looks like this:

MKVToolNix v40.0.0 released

There’s been quite a lot of feedback on the changes in v39, and due to it I decided to make two of the new features configurable: the dark mode for Windows & deriving the file name from the file title. Combine that with an easy-to-trigger regression in the MP4 handling in v39, and I’ve decided to get a new release out sooner rather than later. So here it is, v40.0.0 is out.

You can download the source code or one of the binaries. The Windows and macOS binaries as well as the Linux AppImage are available already. The other Linux binaries are still being built and will be available over the course of the next couple of hours.


  • mkvmerge: MP4 reader: added support for BMP covert art images.
  • MKVToolNix GUI: multiplexer: added an option to disable deriving the
    destination file name from the file title. Implements # 2648.
  • MKVToolNix GUI: multiplexer: the content of the “stereoscopy” combo box has
    been simplified making the box’s minimum width much smaller, allowing the
    user to resize the GUI’s whole window to a much smaller width.
  • MKVToolNix GUI: multiplexer: whenever the user changes the “aspect ratio” or
    “display dimensions” controls, the corresponding radio button will be
    activated automatically. Implements # 2651.
  • MKVToolNix GUI: Windows: added a setting in the preferences to disable the
    GUI’s dark color mode even if Windows’s app color mode is set to
    dark. Implements # 2646.
  • MKVToolNix GUI: Windows: replaced the dark mode introduced in v39 with
    another dark mode that’s less wasteful with space between widgets.

Bug fixes:

  • mkvmerge: MP4 reader: mkvmerge was reading eight bytes too many for cover
    art images. This could cause file identification to fail when the cover art
    was located at the end of the MP4 file. Even if it succeeded, this meant too
    much data present in the attachment. Fixes # 2650.
  • mkvmerge: MP4 reader: covert art images with unknown image types will be
    skipped instead of treated as JPEG images.

Build system changes:

  • Qt 5.9.0 or newer is now required for building MKVToolNix GUI.

Version number 40.0.0
Release status Final
Operating systems Windows 7, Linux, macOS, Windows 8, Windows 10
Website Moritz Bunkus
License type GPL