How to Change the Default Audio Track in MKV

When playing an MKV video file with multiple audio tracks, media players often default to a language or format you do not want. This guide provides a straightforward, step-by-step tutorial on how to permanently change the default audio track of an MKV file using the free software MKVToolNix, ensuring your preferred audio plays automatically every time.

Step 1: Download and Install MKVToolNix

To change the default audio track without re-encoding the video (which preserves original quality), you need a free, open-source tool called MKVToolNix. Download and install the version compatible with your operating system (Windows, macOS, or Linux).

Step 2: Load Your MKV File

  1. Open the MKVToolNix GUI application.
  2. Click on the Multiplexer tab on the left sidebar.
  3. Drag and drop your MKV file into the Source files box, or right-click inside the box and select Add files to browse for your video.

Step 3: Select the Preferred Audio Track

  1. Look at the Tracks, chapters and tags box at the bottom. This section lists all the video, audio, and subtitle tracks inside your MKV file.
  2. Find the audio tracks (they will have an “audio” type icon).
  3. Click on the audio track that you want to set as the default.

Step 4: Change the Track Properties

  1. With your preferred audio track highlighted, look at the Properties panel on the right side of the window.
  2. Locate the Default track flag dropdown menu and change its setting to Yes.
  3. Locate the Forced display flag and set it to Yes if you want to force players to use this track.
  4. Select the other audio tracks in the list and change their Default track flag to No. This prevents media players from getting conflicting instructions.

Step 5: Save and Multiplex

  1. At the bottom of the window, choose your destination folder and name for the new file in the Destination file field.
  2. Click the Start multiplexing button at the very bottom.
  3. The process will take only a few seconds because the software is reorganizing the file headers rather than re-encoding the video.

Once complete, open the new MKV file in your preferred media player, and your selected audio track will play automatically.