Glossary
Session
A grouped window of a user's activity on a site or app, bounded by an inactivity timeout or similar cutoff rule.
Also called: visit
A session is the unit analytics tools use to group a sequence of interactions—page views, screen views, clicks, event tracking hits—that belong to one continuous visit by a single user. It is the basic building block behind traffic counts, bounce rate, and most engagement metrics.
Most tools close a session after a period of inactivity, commonly 30 minutes, or at midnight in the analytics account's time zone. Classic web analytics tools also start a new session when the traffic source or campaign changes mid-visit; GA4 instead ties sessions to a session_start event and applies its own re-engagement rules, so session counts for identical traffic can differ noticeably between tools.
Sessions matter because so many other metrics—engagement rate, pages per visit, average duration—are session-scoped rather than user-scoped. A common pitfall is treating session count as a proxy for unique visitors: one person can generate several sessions in a day, and the same person on a phone and a laptop is usually counted as two separate, unconnected sessions unless identity is resolved through login data or cohort analysis grouping.
Last reviewed September 19, 2026