Sessions vs Users: What's the Difference?

Users counts distinct people (or more precisely, distinct devices/browser identifiers) who visited within the reporting period. GA4 reports both Total Users and Active Users, with Active Users - people who had an engaged session - being the more commonly used default.

Sessions counts periods of activity. In GA4, a session ends after 30 minutes of inactivity or at midnight, and a new one begins the next time that person interacts with the site. One user visiting three times in a week generates one user and three sessions.

The practical difference matters most when reading traffic reports: a spike in sessions without a matching spike in users usually means existing visitors are returning more often, not that reach has grown. A spike in users without a proportional rise in sessions can mean a campaign brought in a lot of new, mostly one-time visitors. Reading the two together, rather than either alone, is what actually tells you whether traffic growth is coming from reach or from repeat engagement.