Session
A session is a group of user interactions with a website or app that happen within a given timeframe. It acts as a container for the pageviews, events, and conversions a single visitor triggers during one visit. Google Analytics 4 starts a session when a user arrives and ends it after 30 minutes of inactivity by default.
Why Sessions Matter
Sessions are the unit most analytics reports count traffic in. Channel, source/medium, and landing page reports measure performance in sessions, not users or pageviews. Metrics like average session duration, sessions per user, and engagement rate all build on the session as their base.
Sessions also carry attribution. The source and medium of the link that starts a session decide which channel gets credit for everything that happens inside it. That makes consistent UTM tagging essential. A mistagged link sends the whole session to the wrong channel. If you tag campaign links with UTM parameters, linkutm’s analytics dashboard shows click data next to the sessions GA4 records.
How GA4 Counts a Session
GA4 logs a session_start event the moment a session begins and assigns it a unique ga_session_id. Every event the visitor fires after that (page_view, scroll, click, purchase) belongs to that session ID. The total session count equals the number of distinct session IDs.
GA4 also flags engaged sessions. A session counts as engaged when it meets any one of these conditions:
- Lasts longer than 10 seconds
- Triggers a key event (conversion)
- Includes at least two pageviews or screenviews
Engaged sessions divided by total sessions produce the engagement rate. A session that fails all three tests is the GA4 equivalent of a bounce, which is why a low engagement rate often signals the same problem as a high bounce rate.
Session Timeout
A session ends after a set period of inactivity, 30 minutes by default in GA4. The timer resets with every interaction, so an active visitor never times out mid-task. If a user leaves a tab open and returns 31 minutes later, GA4 closes the first session and opens a new one.
You can change the limit in Admin, under Data Streams, then Configure tag settings, then Adjust session timeout. The range runs from 5 minutes to 7 hours 55 minutes. Raising the timeout suits content that takes a long time to read or watch. Lowering it suits quick-task tools where a 30-minute gap almost always means a new visit.
Sessions in GA4 vs Universal Analytics
GA4 counts sessions differently from the retired Universal Analytics, and two changes matter most.
- Midnight no longer splits a session. Universal Analytics reset every session at midnight. GA4 does not, so a visit that crosses midnight stays one session.
- Campaign changes no longer split a session. Universal Analytics started a new session whenever the campaign source changed mid-visit. GA4 removed that rule.
Both changes mean GA4 session counts often run slightly lower than UA counts for the same traffic. GA4 also estimates totals from session IDs rather than counting each one exactly, so small reporting differences are normal. For more on how the platform measures traffic, see Google Analytics 4.
Session vs User vs Pageview
These three metrics measure different things and get confused constantly.
- User: one unique visitor, identified by a cookie or signal.
- Session: one visit by that user.
- Pageview: one page load inside a session.
One user can have many sessions, and one session can contain many pageviews. A person who visits on Monday and again on Thursday counts as one user and two sessions. Counting sessions as users overstates your audience size. Counting pageviews as visits overstates your traffic.
Frequently Asked Questions
What is a session in Google Analytics?
A session is a single visit to your site, covering all the pageviews and events one user triggers before they leave or go inactive. GA4 marks the start with a session_start event and a unique session ID. Every interaction during that visit is grouped under the same session.
What is the default session timeout in GA4?
The default session timeout in GA4 is 30 minutes of inactivity. Each interaction resets the timer, so the session only ends after 30 minutes with no activity. You can adjust it from 5 minutes up to 7 hours 55 minutes in your data stream settings.
How is a session different from a user?
A user is one unique visitor, while a session is one visit by that visitor. A single user can start many sessions over days or weeks. So session counts are always equal to or higher than user counts.
Does GA4 start a new session at midnight?
No. GA4 keeps a visit that crosses midnight as a single session. This differs from Universal Analytics, which reset all sessions at midnight and inflated session counts for late-night visits.
Run your tagged links through linkutm’s GA4 URL tester to confirm every session lands with the right source and medium.