MKV Set Default Track

Change which audio or subtitle track is marked as default in a Matroska container. Does not re-encode or mux; only updates metadata flags.

When to use

• User wants a different audio or subtitle track to play by default
• After acquiring a multi-language rip, set the preferred language as default
• Unset defaults from other tracks in the same type (e.g., only one audio track should be default)

Inputs to gather

• File — path to MKV file (required)
• Track index — the track number to set as default (required; from mkv-track-list)
• Unset others — boolean flag; if true, unset default flags on all other tracks of the same type (optional, default: false)

Procedure

1. Check mkvtoolnix is installed