mkv

MKV, or Matroska Video, is a multimedia container format developed as part of the Matroska project. It is designed to store multiple video, audio, subtitle tracks and metadata in a single file. MKV is an open, extensible standard built around EBML, an XML-like binary format that allows flexible data structures.

Because MKV is a container rather than a fixed encoding, it can include video codecs such as H.264/AVC, H.265/HEVC, VP9, and AV1; audio codecs like AAC, MP3, Vorbis, and Opus; and subtitle formats including SRT, ASS/SSA, and VobSub. It also supports multiple audio tracks, subtitle tracks, chapters, and attachments (cover art, fonts).

File extensions: .mkv for video files; .mka for audio-only; .mks for subtitles; there are variants such as .mk3d for 3D content.

Compatibility and usage: widely supported by media players and tools such as VLC, MPV, MPC-HC, Kodi, and FFmpeg. MKV is favored for archiving due to its flexibility and robustness; licensing is open, with no patent requirements for the format itself.

History: development began in the early 2000s within the Matroska project; named after the Matryoshka dolls. The project aims to provide a free, open container standard to supersede proprietary formats. The Matroska project maintains specifications at matroska.org.