Since .mkv (Matroska) is a flexible container format, it may contain high-quality video, multiple audio tracks, or subtitles. Standard players like Windows Media Player may not support it without extra codecs.
💡 If the video shows "green screen" or has no sound, it likely uses a high-efficiency codec (like HEVC/H.265). Updating VLC usually fixes this immediately.
Use HandBrake to convert while maintaining high resolution.
Download and use VLC Media Player . It is free and plays almost any MKV file without extra setup.