Average session duration

Average session duration is the mean length of time visitors spend in a session, from the first recorded interaction to the last. It is typically reported as total session duration ÷ number of sessions.

How it is actually calculated is a common source of confusion. Classic, timestamp-based tools measure duration as the gap between the first and last hit in a session, which means a single-page session with no second interaction is recorded as zero seconds even if the visitor spent minutes reading — this drags the average down whenever bounce rate is high. Newer platforms instead track "engaged time," using periodic signals sent while a tab is in the foreground, which captures time spent on single-page sessions that the older method missed; the two approaches are not directly comparable.

Average session duration is a rough proxy for engagement and content quality, useful alongside pages per session and scroll depth for judging whether traffic is actually reading or using a site. It is heavily skewed by outliers — a handful of sessions left open in a background tab for hours can distort the mean — so practitioners often check the median or distribution rather than trusting the average alone, and always confirm which measurement method a platform is using before comparing numbers across tools.