In GA4, users count people, and sessions count a single visit in which that person used your site or app. Among sessions, those that lasted longer than 10 seconds, had a key event, or viewed 2 or more pages are called engaged sessions. The share of engaged sessions among all sessions is the engagement rate, and the rest is the bounce rate. In this post, I've summarized what each of these metrics counts.
While looking at GA4 reports, you've probably wondered at least once, "There are way more sessions than users. Is that right?" or "Why is this so different from the bounce rate I used to see?" The metric names may look familiar, but GA4's definitions often differ a little from what you'd expect. Comparing numbers without knowing the definitions can easily lead to the wrong interpretation, so in this post I'll go through the definitions of users, sessions, and engagement metrics one by one.
1. Who counts as a user in GA4?
The user metrics help article describes four core metrics for counting users.
| Metric | Official definition |
|---|---|
| Total users | The number of unique users who triggered at least one event during the period |
| Active users | The number of unique users who engaged with your site or app during the period |
| New users | The number of unique users who logged a first_visit (web) or first_open (app) event during the period |
| Returning users | The number of unique users who had previously started a session, during the period |
The most important one here is active users.
On the web, a user is counted as active if they had an engaged session, or if a first_visit event or an engagement time value (the engagement_time_msec parameter) was collected.
According to the dimensions and metrics help article, the number labeled "Users" in reports is exactly this active users figure.
So you can think of the user count in reports as closer to "people who engaged" than "everyone who came in."
The same help article explains that not all new users are active, so new users can come out higher than active users. That's because a user who came to the site and left quickly without doing anything is included in total users but may not be included in active users.
2. When does a session start and end?
The sessions help article defines a session as the period during which a user interacts with a website or app.
When there's no session in progress and a user views a page or screen or opens the app in the foreground, a session starts, and a session ID is created along with the session_start event.
- When it ends: By default, a session ends after 30 minutes of inactivity. There's no limit on the length of the session itself.
- Adjusting the timeout: You can change the session timeout in hours and minutes in the web stream's tag settings.
- How it's counted: GA4 calculates the session count by estimating the number of unique session IDs.
- Session number: Each session gets a
ga_session_numberalong withga_session_id, which shows which session this is among all the sessions the user has started so far.
A café analogy makes it easy to understand. One customer is a user, and one visit that customer makes to the café is a session. The default rule is that if they leave their seat for more than 30 minutes and come back, it counts as a new visit, which is why one user can create several sessions in a day.
For reference, according to the UA vs. GA4 comparison help article, the old Universal Analytics (UA) started a new session when midnight passed or new campaign parameters came in, but GA4 doesn't. That's one of the reasons UA and GA4 session counts looked different.
3. What conditions make an engaged session?
The engagement rate and bounce rate help article treats a session as engaged if it meets any one of the following.
- A session that lasted longer than 10 seconds
- A session with a key event
- A session with 2 or more page or screen views
The 10-second criterion is worded slightly differently across help articles, as "longer than 10 seconds" in some and "10 seconds or longer" in others, but either way the default is 10 seconds.
You can change this threshold in seconds under "Adjust timer for engaged sessions" in the tag settings help article.
It's also worth knowing that the first_visit, first_open, and session_start events are excluded from the engaged session calculation even if you mark them as key events.
So how are those 10 seconds measured?
According to the user engagement help article, GA4 records the time a web page is in focus and the time an app screen is in the foreground, and sends it as the engagement_time_msec parameter.
That means time spent with the tab merely left open while you're looking at another window isn't counted as engagement time.
4. How are engagement rate and bounce rate related?
The two metrics are two sides of the same coin.
| Metric | Calculation |
|---|---|
| Engagement rate | Engaged sessions ÷ total sessions |
| Bounce rate | Sessions that weren't engaged ÷ total sessions |
As in the help article's example, if a user reads a post for less than 10 seconds and leaves without any other event or page navigation, that session isn't an engaged session. If that's the only session on the site, the engagement rate is 0% and the bounce rate is 100%. In other words, in GA4, engagement rate and bounce rate always add up to 100%.
If you've used UA, you should note that the meaning of bounce rate has changed. According to the UA vs. GA4 comparison help article, UA's bounce rate was the percentage of sessions that viewed only one page and ended without interaction, so even reading a post carefully for several minutes and leaving counted as a bounce. In GA4, the same case becomes an engaged session if the user stayed longer than 10 seconds, so comparing the two tools' bounce rates directly doesn't work.
Finally, engagement rate and bounce rate aren't shown by default in most reports. If you have Editor permission or higher, you can add the metrics through "Customize report" in a detail report.
Summary
Users in GA4 reports are active users, meaning people who engaged, and a session is a single visit that ends after 30 minutes of inactivity by default. An engaged session is one that lasted longer than 10 seconds, had a key event, or viewed 2 or more pages, and engagement rate and bounce rate are inverses of each other based on these engaged sessions. For detailed metric definitions and setup steps, please refer to the official help articles linked in the post.
FAQ
- Is the user count in GA4 reports total users or active users?
- It's active users. The official help explains that the active users metric is displayed as "Users" in reports.
- How many minutes until a GA4 session ends?
- By default, after 30 minutes of inactivity. You can change the session timeout in the web stream's tag settings, and there's no limit on the length of the session itself.
- Is GA4 bounce rate the same as UA bounce rate?
- No. GA4 bounce rate is the percentage of sessions that weren't engaged, the inverse of engagement rate, while UA bounce rate was the percentage of sessions that viewed only one page and ended without interaction.
Related posts
- GA4 events and parameters basics - The automatically collected events that create engagement time and sessions
- GA4 conversion lookback window, now configurable by the day - About key events, one of the engaged session conditions
- Understanding attribution models with Google Analytics - How to interpret sessions and conversions by channel