Drops before start

The Drops before start metric counts sessions where the viewer quit before any main content rendered. The metric flags pre-content abandonment regardless of ad behavior, so it is the best measure of pure pre-content drop-off. Pair it with Media starts and Content starts to compute the share of sessions that never produced a content frame.

How this metric is calculated

The media backend sets this flag for sessions that close without ever producing a play event on main content. The metric is reported on the close call. Common scenarios include: the viewer exits during a pre-roll ad, the player stalls indefinitely in the initial buffer phase, or an error fires before the first main-content play event. In all these cases the session records a Media start but no Content start, and no Progress markers are recorded.