# 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.

Video master

Adaptive streaming

Adaptive playback

Adaptive streaming packages one source into aligned renditions that a player selects segment by segment. This diagram shows streaming broadly, not specifically HLS Streaming.

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## 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.

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## Key facts

1. 1A 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.
2. 2The 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.
3. 3Low-Latency HLS adds partial segments, preload hints, and blocking playlist reload behavior; simply shortening ordinary segments does not implement the complete low-latency mode.

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## 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.

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## Common use cases for streaming

These examples cover streaming broadly, not specifically HLS Streaming.

* Delivering long-form, episodic, educational, live, or user-generated video over variable networks.
* Providing low-bandwidth through high-resolution renditions from one master.
* Combining captions, alternate audio, encryption, thumbnails, and ad markers with playback media.

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## Working with streaming

This guidance covers streaming broadly, not just HLS Streaming.

An encoder creates several quality levels, and a packager divides them into aligned segments referenced by a manifest. During playback, the client estimates throughput and buffer health, then requests an appropriate segment from one rendition at a time.

Streaming quality depends on the relationship between renditions, segments, manifests, players, and the network. A valid encode can still perform poorly if keyframes are misaligned, the ladder is inefficient, or the player cannot switch cleanly.

### What you gain

* Segmented delivery lets playback begin without downloading the entire program.
* Multiple renditions let a player adapt quality as network and device conditions change.
* HTTP-based protocols can reuse ordinary web caching and delivery infrastructure.

### What it costs

* Short segments can reduce switching and live latency but increase request and packaging overhead.
* A dense rendition ladder offers finer adaptation while increasing encoding, storage, and cache cost.
* More aggressive quality selection can improve sharpness but raises rebuffering risk on unstable networks.

### Before production

1. 1Test the rendition ladder on slow, changing, and high-latency connections.
2. 2Align segments and keyframes, then validate manifests in the target players.
3. 3Measure startup, rebuffering, quality switches, CDN efficiency, and playback failures.

[← HLS Packaging](/glossary/hls-packaging.md)[hls.js →](/glossary/hls-js.md)

More in streaming

* [FVOD](/glossary/fvod.md)
* [HDS Streaming](/glossary/hds-streaming.md)
* [HLS Packaging](/glossary/hls-packaging.md)
* [hls.js](/glossary/hls-js.md)
* [HLSe](/glossary/hlse.md)
* [HTTP Smooth Streaming](/glossary/http-smooth-streaming.md)

[All 505 terms](/glossary.md)

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