What is HLS Streaming?
HTTP Live Streaming delivers segmented media over HTTP through M3U8 playlists. A master playlist can describe multiple bitrate, resolution, audio, and subtitle renditions.
How HLS Streaming works
HLS is a client-driven adaptive delivery system: the player retrieves playlists, chooses a rendition, downloads media units, and revises its choice as conditions change. Because requests use HTTP, segments can pass through standard caches and content delivery networks. Live playlists expose a moving window, whereas on-demand playlists describe a stable finite presentation. The protocol connects encoded renditions to playback, with latency and resilience shaped by playlist updates, segment sizing, and client buffering.
Key facts
- A master playlist lists variant streams and rendition groups, while each media playlist orders the segments for one track or multiplexed presentation; confusing the two breaks discovery logic.
- The EXT-X-TARGETDURATION and media-sequence tags help clients interpret a live window. EXT-X-DISCONTINUITY is required for changes in file format, track layout, or timestamp sequence, and recommended for changes in encoding parameters or sequence.
- Low-Latency HLS adds partial segments, preload hints, and blocking playlist reload behavior; simply shortening ordinary segments does not implement the complete low-latency mode.
When HLS Streaming matters
Developers choose HLS for scalable live or on-demand delivery across browsers, mobile devices, and televisions. Codec support and native playback behavior still vary by client.