Bitrate switching is an adaptive player changing the quality level, or rung of the bitrate ladder, partway through a stream as network conditions move. It happens because an ABR player picks a rendition for each few-second segment, upshifting when the buffer cushion is deep and downshifting before it runs dry, so switching is the visible trace of that segment-by-segment bet. It is measured as switches per session from logged rendition changes, a non-standard player hook rather than a standard media event, which makes switching telemetry more fragile across platforms than startup or rebuffering. The catch cuts both ways: too few switches can mean the player is stalling instead of adapting, while frequent switching is its own visible artifact that unsettles the picture even when the average bitrate looks healthy. It sits at the heart of the ABR trade-off, weighed against the average bitrate played and the rebuffering ratio.
