Startup time, also called time to first frame, video start time, or join time, is the wait between the moment a viewer asks for a video and the moment its first frame is painted on screen. It is the first quality judgment any stream receives and is measured from player events as play intent in, first rendered frame out, not as time-to-first-byte and not from manifest load. A causal study of a large Akamai dataset found abandonment stays near zero up to about two seconds, then rises roughly 5.8 percentage points for each additional second, so the start is where viewers are lost before watching anything. Its catch is survivorship bias: only sessions that started have a startup time, so it must be read beside video start failure and exit-before-video-start, and reported as median plus 95th percentile. The start buffer threshold is usually the largest controllable component, tuned against rebuffering.
