Session length

Session length is the duration of a single, continuous visit to a product, measured from the first recorded action until the session is considered ended, most often after a fixed period of inactivity (commonly around 30 minutes, though the exact cutoff is configurable and varies by platform and tool).

It is typically reported as an average or median across sessions in a period, since a small number of very long or very short sessions can distort a simple mean. Session length differs from engaged time, which tries to measure time the user was actually active and attentive rather than simply the clock time between a session's start and its inactivity timeout — a tab left open in the background can inflate session length without reflecting real engagement.

Session length matters as a rough proxy for depth of engagement, but it needs care in interpretation: a longer session can mean a user is deeply engaged, or it can mean they're struggling to complete a task that should have been quick. It's more informative combined with what happened during the session — actions taken, value delivered — than as a number on its own. Common pitfalls include comparing session length across very different product types (a quick-task utility app should have short sessions by design, unlike a media or gaming app), and letting crashes artificially truncate sessions, which lowers average length for reasons unrelated to engagement.