Unique viewers

Studio estimates this rather than counting it. The figure deduplicates across devices, includes signed-in and signed-out viewing, and is available for periods of up to 90 days. On Shorts it is estimated from engaged views, so it reflects the people who stayed rather than everyone the feed played it to.

The common error is arithmetic. Unique viewers from two separate months cannot be added together, because anyone who watched in both appears in both figures. The number also sits far below your view count on any channel with loyal viewers, which is normal. Read it for reach, and read returning viewers next to it to see how much of that reach is the same crowd coming back.