What Is a Session? The Difference From PV and UU, and How to View It in GA4

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"When I open GA4, sessions, views, and users are all lined up, and I don't know which one to look at." "I can't clearly explain the difference between sessions and page views." The "session" metric is one that people who have just started with access analytics often stumble over.
This article organizes, while keeping technical jargon to a minimum, the meaning and counting of sessions, the difference from the easily confused page view and unique user metrics, how to view them in GA4 and points to watch, and the points to keep in mind when interpreting sessions. By the time you finish reading, you should be able to read GA4 sessions correctly and use them in combination with other metrics.
What a Session Is
A session is a metric that counts as one the series of activity making up a single "visit," from when a user arrives at the site until they leave. The stretch of activity from a user arriving at the site, viewing several pages, and then leaving is counted as one session. It is one of the basic metrics of access analytics, representing "how many times the site was visited."
For example, if one user arrives at the site and views three pages—top page → article A → article B—the number of pages viewed (PV) is 3, but because the visit is a single continuous flow, the session count is 1. If that user leaves the site once and revisits on the same day, the session count becomes 2. In other words, sessions represent not "how many pages were viewed" but "how many times the site was visited."
Because sessions serve as the axis for measuring how many visits each inflow channel—ads, SEO, social, and so on—is acquiring, they are an important metric for evaluating the effectiveness of acquisition initiatives.
How Sessions Are Divided
A session is "a series within a visit," but there are rules for where it is divided. In GA4, sessions are divided mainly at the following times.
- When inactivity continues for a set period: in GA4's default setting, if there is no operation for 30 minutes the session ends, and operating again starts a new session.
- When the date changes: crossing midnight in that time zone is treated as a separate session even if activity is continuous.
Note that in the old Analytics (Universal Analytics), sessions were also divided "when the referrer (inflow channel) changed midway," but in GA4 this rule has been abolished. As a result, GA4 and the old UA count sessions differently, and the figures will not match even for the same site—a point that requires caution.
The Difference Between Sessions, Page Views, and Unique Users
To use sessions correctly, the shortcut is to grasp the difference from page views and unique users, which are often discussed alongside them. The three differ in "what they count."
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