A multi-variant playlist is an .m3u8 file that does not contain media segments. Instead it lists the URLs of media playlists for each rendition the player can pick from. Each rendition is described by an #EXT-X-STREAM-INF tag carrying its bandwidth, resolution, frame rate, codec string, and any audio/subtitle group references. The player downloads the multi-variant playlist first, picks a starting rendition based on its initial bandwidth estimate, and then operates on that rendition's media playlist.
A typical multi-variant playlist for VOD might list 6 video renditions (360p, 480p, 720p, 1080p H.264 and 1080p, 4K HEVC), one audio group with 3 languages and one subtitle group with 5 languages. The player composes a final stream by picking one video rendition plus one audio variant plus optionally one subtitle. ABR switches happen by jumping between video renditions at segment boundaries — the audio and subtitle stay constant.
Apple's 2020 renaming reflects the broader industry shift away from terms like "master" and "slave". The HLS Authoring Specification consistently uses "multi-variant" since the 2020 revision; tools like Shaka Packager and Bento4 followed. References to "master playlist" still appear in older code, blog posts and documentation but are deprecated in current Apple guidance.
