MKV is the file extension of Matroska, an open, royalty-free container format first released in 2002. Its defining feature is flexibility: an MKV can hold practically any video codec, any audio codec, any number of audio and subtitle tracks, chapters, cover art and even attached fonts, all in one file.
What’s often inside an MKV
| Track | Common formats |
|---|---|
| Video | H.264, HEVC, VP9, AV1 |
| Audio | AAC, AC-3 (Dolby Digital), E-AC-3, DTS, TrueHD, FLAC, Opus |
| Subtitles | SRT, ASS/SSA (styled text), PGS (Blu-ray images) |
| Extras | Chapters, attachments, multiple languages |
That range is why MKV is popular for films and series, game and screen recordings (OBS Studio offers MKV because a crash doesn’t corrupt the whole recording), and archiving discs with every audio language and subtitle intact.
Why MKV doesn’t play everywhere
The same flexibility makes MKV harder to support. A device has to handle not just the container but whatever codecs are inside. iPhones and iPads, many smart TVs, game consoles and editors such as iMovie and Premiere Pro either don’t open MKV or play it without sound. On computers, VLC and mpv play almost any MKV.
Missing sound is the most common MKV problem. Surround formats such as Dolby Digital (AC-3) and DTS need licensed decoders that browsers, many apps and some TVs don’t include.
MKV and WebM
WebM is a restricted subset of Matroska: the same structure, limited to the open codecs VP8, VP9 and AV1 for video and Vorbis or Opus for audio. That restriction is what lets every browser play WebM, while MKV support varies.
MKV or MP4?
Keep MKV for archiving, especially when you want several audio languages and subtitle tracks in one file. Convert to MP4 with H.264 and AAC when the video needs to play on phones, TVs, in editors or on websites. The conversion is quick and lossless when the MKV already uses H.264.