In this guide, we will explain what a session is in Google Analytics 4 (GA4), why session duration matters, which session metrics are available, and how to configure these settings.

What is a Session in GA4?

A session represents the group of interactions a user has with your website or mobile app within a given time frame. A session starts when a user arrives on your site and ends when there is no interaction (such as a page view, click, or a custom event trigger) for a certain period.

In GA4, the default session timeout duration is 30 minutes. This means if a user takes no action for 30 minutes, the session ends. If the user returns later, a new session will start.

Why is Session Duration Important?

Session duration is a critical setting for accurately analyzing how users interact with your website or app. If misconfigured, it can lead to:

• Misinterpretation of user behavior:
  For example, if a user spends 40 minutes reading a blog post without clicking anywhere, a short session timeout might cause GA4 to count it as two separate sessions. This does not reflect the real user experience.

• Performance marketing and conversion metrics:
  Artificial increases or decreases in session count can skew your campaign performance reports.

• Fragmented user journeys:
  If users browse in multiple tabs or take long pauses between actions, sessions may split, causing loss of continuity in analytics.

How Session Timeout Impacts the “(not set)” Data Issue

Setting a very short session timeout in GA4 can cause some sessions to end before any interaction occurs. In such cases, GA4 may fail to capture critical attribution data such as source, campaign, or medium, resulting in “(not set)” values in reports.

This issue is especially common if users bounce quickly or remain idle for long periods. Over time, this increases the percentage of incomplete data, reducing the accuracy of your analysis and potentially harming marketing decision-making.

Optimizing the session timeout based on your needs can help reduce the “(not set)” rate and improve your data quality.

How to Configure Session Timeout in GA4

GA4 allows you to set session timeout between 5 minutes and 7 hours 55 minutes. You can shorten or extend this period depending on the nature of your website or app.

Steps to change session timeout:

1- Sign in to your Google Analytics account and select the desired GA4 property.

2- Click the Admin panel in the bottom-left corner.

3- Go to Data Streams and select your web data stream.

4- Click Configure tag settings.

5- Select Adjust session timeout.

6- Set the desired session duration in minutes or hours.

Engaged Sessions and Engagement Time

GA4 not only counts all sessions but also classifies those with meaningful interactions as Engaged Sessions.

Criteria for an Engaged Session:

A session is considered “engaged” if at least one of the following occurs:

• Two or more page views or screen views

• At least one conversion event (key event)

• The user stays on the site for at least 10 seconds (default)

In some cases, the default 10-second threshold may be too short—especially if your site has long load times or deep engagement. Increasing this threshold can improve measurement accuracy.

Adjusting Engagement Time

In GA4, you can set the minimum time required for a session to be counted as engaged between 10 and 60 seconds. A longer duration helps filter out low-quality or accidental visits.

GA4 Session Metrics

• Sessions: The total number of sessions started within a given time period.

• Engaged Sessions: Sessions meeting the above engagement criteria.

• Engaged Sessions per User: Total engaged sessions divided by total users.

• Engagement Rate: Engaged sessions as a percentage of all sessions.

• Bounce Rate: The percentage of sessions with no engagement (the inverse of engagement rate).

How GA4 Counts Sessions and Session ID

In GA4, each session is tracked via a session_start event, which generates a unique ga_session_id. This ensures that separate visits by the same user are recorded as distinct sessions.

If a user remains inactive for 30 minutes (or the duration you’ve set), the session ends. If they return later, a new session begins.

Conclusion

Correctly configuring session timeout and engaged session settings in GA4 helps you better understand user behavior and optimize marketing performance. Adjusting session duration to fit your needs ensures your reports remain accurate and meaningful.