Session Duration is a measure of how long people spend on your site when they visit, on average.
You’ll see Session Duration show up in the Quick Stats of every page as well as in the table of the Referrer, Geographic, and Campaigns menus.
When someone arrives on your site, a new session is created, and each page they view is included in this session. The session concludes when there is a thirty-minute period of inactivity.
To calculate the duration of a session, we take the time of each view and subtract it from the previous one. For instance, imagine a session has views at the following times:
- Page 1: 1:23pm
- Page 2: 1:25pm
- Page 3: 1:27pm
From this data, the session duration would be calculated as 4 minutes. While this works reasonably well, there is a drawback.
We know they spent 2 minutes on Page 1 and Page 2, but we don’t know how long they spent on Page 3, so that data is simply omitted.
Omitting the time spent on the last page lowers the average session duration, but since single-page sessions are also excluded (they tend to be brief), this has the effect of increasing the average session duration. In practice, the value is approximate but accurate enough to get a clear picture of engagement and see similar results over time.
This is similar to how Google Analytics calculates session duration, so the values should be similar when switching to Independent Analytics.
Why do I see “-” instead of a session duration?
If you’re looking at the table in a report, such as the Referrers report, you may see some referrers with a session duration of “-” instead of a real duration.
When a visitor views only one page before leaving, Independent Analytics cannot determine how long they spent on the site. If you have a referrer with 5 visitors and the session duration is omitted (-), it means all 5 visitors viewed only one page. You’ll also see that the bounce rate is 100%. If even one of them viewed a second page, Independent Analytics could calculate an average duration. For this reason, the issue of missing session durations usually resolves itself as more visitors arrive.
