Master vs media playlists
An HLS stream starts with a master playlist that lists variant streams at different bitrates. Each variant points to a media playlist that lists the actual segments. A player reads the master first, then picks a variant that suits the current bandwidth.
Adaptive bitrate
The core value of HLS is adaptive bitrate switching. The player measures throughput and buffer health, then moves up or down the variant ladder to avoid stalls while keeping quality as high as the connection allows.
Alternate renditions
- Multiple audio tracks (languages, commentary)
- Subtitle and closed-caption tracks
- Alternate video angles where provided
Low-latency HLS
Low-latency HLS reduces the gap between live and playback using partial segments and playlist blocking. It requires both server and player support to work end to end.