Sessions

A session is a single visit to your site by one person. In GA4 it begins with the session_start event and ends after 30 minutes of inactivity by default. Come back the next day and that's a new session, even though you're the same person. So sessions count visits, not people — one user can rack up many sessions over a week. It's the most common way to measure how much your site is being used.

Why it matters

Sessions are the workhorse traffic metric. When someone says traffic is "up" or "down", they usually mean sessions. They're a good measure of activity over time and the natural denominator for rates like engagement rate. But because a session is a visit rather than a visitor, the number answers "how many visits?" and not "how many people?" — a distinction that trips up a surprising number of reports.

A concrete example

You check GA4 and see 1,200 sessions last week, up from 900. Good news — more visits. But a single referral source might account for most of the rise, and those visitors might have left immediately. Sessions told you volume went up; they didn't tell you whether the visits were any good. For that you'd read engagement and your key events next to the session count.

The common misreading

The most frequent error is treating sessions as unique visitors. They aren't. A loyal reader who visits daily generates seven sessions a week but is one user. The other trap is the 30-minute timeout: a person who steps away mid-task and returns 40 minutes later counts as two sessions, which can quietly inflate the number on slow-burn tasks.