HLS (HTTP Live Streaming) is Apple's segmented adaptive-streaming protocol, standardized as IETF RFC 8216. It breaks a stream into short segments listed in an M3U8 playlist (the manifest); the player downloads the playlist, then fetches segments over ordinary HTTP, switching between renditions as the network changes. Because it rides plain HTTP, it traverses firewalls and caches in any CDN with no special infrastructure.
HLS is effectively mandatory: it is the only protocol natively supported by Apple's Safari, iOS, and tvOS, so any platform that wants Apple devices must serve HLS. It is also widely supported elsewhere, which makes it the most universal delivery format.
Modern HLS uses fragmented-MP4/CMAF segments (rather than the legacy MPEG-TS), which lets the same segments serve DASH too, and supports Low-Latency HLS (LL-HLS) for live. Its DRM path is FairPlay with the cbcs encryption scheme.
