What is engagement time?
Engagement time is the total amount of time a user spends actively engaged with your website or app.
"Actively engaged" means the page or app is in the foreground and visible to the user.
Engagement time is counted when the user is:
- Reading content on a visible, focused tab.
- Scrolling through a page.
- Watching a video in the foreground.
- Simply keeping the page open and in focus (no clicks or scrolls required).
Engagement time is not counted when:
- The browser tab is in the background.
- The app is minimised or in the background.
- The page is not visible (e.g. another window covers it).
- The session has ended.
So engagement time is not the same as wall-clock time, session duration, or passive open time.
A user who opens your page and immediately switches to another tab accumulates zero engagement time, even if the tab stays open for an hour.
What is engagement_time_msec?
engagement_time_msec is an event parameter in GA4 BigQuery that carries a portion of the accumulated engagement time (in milliseconds).
Think of it this way: