What you should know
MKV (Matroska) is an open container launched in 2002, able to hold an unlimited number of video, audio and subtitle tracks in a single file. It is the format of choice for multi-language series and films.
Unlike AVI or MP4, Matroska assumes nothing about the codec: it can carry H.264 as easily as VP9, AV1 or FLAC. That is both its strength and the reason it demands a capable player.
Strengths
- Multiple tracks (languages, commentary) and subtitles in one file
- Accepts practically every audio and video codec
- Open format, widely supported by VLC and modern players
- Very rich chapter and track metadata
Limitations to know
- No native support on many TVs and hardware players
- Not played directly by Safari or Windows Media Player
- Multi-track files are complex to convert without losing data
- Poorly suited to sharing on mainstream platforms
When to use it
Keep MKV to archive a work with several audio tracks and subtitles, and to watch on a computer with VLC. To cast to a TV, send to a relative or publish online, convert to MP4 and choose which audio track to keep.
Quality, size and compatibility
MKV forces no re-encoding: if it already holds H.264, a conversion to MP4 can copy the video track untouched. The difficulty comes from multiple tracks: only the selected ones survive, and subtitles do not always follow.
Frequently asked questions
- Is MKV better than MP4?
- Neither better nor worse: it is a more flexible container. MP4 wins on compatibility, MKV on track richness. The choice depends on usage, not on image quality.
- Why does my MKV conversion lose the subtitles?
- MP4 stores subtitles in a different format, and many tools ignore them when copying tracks. You need to extract them separately if you need them.