What Is a Session in Google Analytics?

A session in Google Analytics is a group of user interactions on your site within a given time window — GA4 starts one with a session_start event and ends it after 30 minutes of inactivity by default. Sessions are not the same as users (one user can have many sessions) or pageviews (one session can have many pageviews). GA4 also counts sessions differently than Universal Analytics did, which is why the numbers rarely match after a migration.

How a session starts and ends

A GA4 session begins the moment a session_start event fires — the first time a user lands on your site (or opens your app) after not having an active session already running. Every event that follows, from page_view to scroll to a custom key event, gets bucketed into that same session until it ends.

By default, a session ends after 30 minutes of inactivity. If a visitor closes the tab, walks away, or just stops interacting, GA4 waits 30 minutes and then closes the session out. You can adjust this timeout in Admin > Data Streams > [your stream] > Configure tag settings > Session timeout, anywhere from 5 minutes up to a maximum of 7 hours 55 minutes.

One thing that surprises people migrating from Universal Analytics: if a user arrives organically, leaves, and comes back later the same day through a paid ad with a UTM link, GA4 starts a brand-new session by default. A change in campaign source mid-visit — or after a gap — is treated as the start of a new visit, not a continuation of the old one.

Sessions vs. users vs. pageviews

These three metrics answer different questions, and mixing them up is one of the most common GA4 reading mistakes. Users counts unique people (or devices) who visited — one person is one user no matter how many times they come back. Sessions counts visits — that same person generates a new session every time they return after a timeout or a qualifying campaign change. Views (pageviews) counts individual page loads — a single session commonly includes several page views as someone clicks around your site.

So a returning reader who visits your blog three times in a week is 1 user, 3 sessions, and however many page views they racked up across all three visits. None of these numbers should match, and that's expected. For more on how GA4 turns raw activity into a duration figure, see average session duration.

Why GA4 session counts don't match Universal Analytics

If you migrated from Universal Analytics, your GA4 session count almost never lines up with your old UA numbers for the same period — and that mismatch has caused a lot of unnecessary panic about "losing traffic." It's a counting-method difference, not an actual drop.

UA reset sessions at midnight, site time zone. A single visit that ran from 11:58pm to 12:05am counted as two sessions in UA, but as one continuous session in GA4, since GA4 has no midnight cutoff.

UA's rule for restarting a session on a new campaign source was also slightly different from GA4's, and GA4's engagement-based model changes what counts as an "active" interaction in the first place — which also affects event count totals. Stack these differences together across millions of visits and you get a noticeably different session total, even though the underlying traffic didn't change.

FAQ

What triggers a new session in GA4?

A new session starts after 30 minutes of user inactivity (by default), or when a user arrives with a new campaign source/medium mid-visit, such as clicking a paid ad UTM link after an earlier organic visit.

Can I change the 30-minute session timeout in GA4?

Yes. Go to Admin > Data Streams > [your stream] > Configure tag settings > Session timeout, and set anywhere from 5 minutes up to the maximum of 7 hours 55 minutes.

Why is my GA4 session count lower than my old Universal Analytics count?

GA4 doesn't split sessions at midnight the way UA did, and it uses a different, engagement-based model for what counts as active. Both changes tend to produce fewer, more consolidated sessions than UA reported for the same traffic.

Is a session the same as a visit?

Yes, "session" and "visit" refer to the same thing in Google Analytics — a session is simply GA4's term for a single visit to your site or app.

Related terms

• What Is Average Session Duration in GA4?GA4 measures engaged time, not "tab open" time — and that changes what's a good number.
• What Is Event Count in Google Analytics?Every single hit is an event in GA4. Here's why that number looks so big.
• What Are Key Events in GA4?GA4 renamed "conversions" to "key events" in 2024 — here's what actually changed.