HLS (HTTP Live Streaming) is a streaming protocol originally developed by Apple that delivers video by breaking it into short segments — typically two to six seconds each — and publishing an M3U8 playlist file that lists the available segments and their URLs. A master M3U8 contains references to per-rendition playlists, each describing the segments for one quality level; this two-level manifest structure is the foundation of ABR in HLS. The player downloads the master playlist, reads the available renditions, selects an initial quality based on current bandwidth estimation, and then fetches segments sequentially using plain HTTP GET requests — the same requests any browser makes for images or scripts, which means HLS traverses corporate firewalls and proxies without special network configuration. HLS is supported natively in Safari and iOS, and via Media Source Extensions (MSE) in Chrome, Firefox, and Edge using JavaScript players such as hls.js or Video.js. For learning video, HLS is the near-universal choice because of its device support breadth, its compatibility with CDN edge caching, and its tolerance for the intermittent connectivity common in mobile and corporate Wi-Fi environments. The alternative protocol MPEG-DASH is technically similar and vendor-neutral but has less complete native support on Apple devices. Low-Latency HLS (LL-HLS), introduced for live streaming, reduces glass-to-glass delay below two seconds, relevant for live virtual classrooms that record and replay via the same HLS pipeline.
The handbook · 7 volumes
Fora Soft Video Engineering Handbook
HLS is the default way learning video reaches browsers and phones, and its segment and ladder settings decide startup time and stalls. We wrote seven volumes that cover the whole video stack; for HLS start with Volume 2, which covers HLS, CMAF, segment packaging and latency budgets, with Volume 1 on encoding and Volume 3 on ABR and players. Written by Nikolay Sapunov, CEO at Fora Soft.
Is your HLS setup causing slow starts or stalls for learners?
We will review your HLS packaging, segments and ladder and give you settings that cut startup time and stalls, with expected CDN costs. 250+ video products shipped since 2005.
