Rebuffering ratio is the share of a streaming session the viewer spent stalled rather than watching, defined as total stall time divided by stall-plus-play time and expressed as a percentage. It counts only the mid-playback freezes that occur after the buffer runs dry, with the initial startup wait and user-initiated seeks excluded, so the number is computed from player events under standards such as CTA-2066, never from the pixels. It is the streaming QoE metric most strongly tied to abandonment: a causal study found a stall equal to just 1 percent of a video's length cost about 5 percent of watch time, and buffering ratio carries the largest single effect on engagement across all content types. Its catch is that the ratio alone hides whether one long freeze or many short ones caused it, so it is read alongside rebuffering frequency and duration, and against the bitrate ABR trades for smoothness.
