Adaptive Bitrate Streaming

Definition

Adaptive bitrate (ABR) streaming is a video delivery technique where the player dynamically switches between multiple pre-encoded versions of the same video — each at a different quality level and bitrate — based on the viewer's current network speed and device capability. Rather than locking a viewer into a single fixed-quality stream, ABR continuously monitors bandwidth and buffer health, stepping up to higher quality when the connection is strong and stepping down to avoid stalling when it weakens. The most widely used ABR protocols are HLS (HTTP Live Streaming) and MPEG-DASH, both of which segment video into small chunks (typically 2–10 seconds each) and serve them via a manifest file that lists all available quality tiers. When a viewer presses play, the player fetches the manifest, begins downloading segments at an appropriate quality level, and re-evaluates that choice with every new segment. This results in a viewing experience that is largely buffer-free even on unstable connections, at the cost of some momentary quality fluctuation. For content creators and platforms, implementing ABR requires encoding each video into multiple renditions (e.g., 360p, 480p, 720p, 1080p) and hosting them on a CDN for fast global delivery.