What causes (not set) Landing pages in GA4?

A while back Google added the landing pages report back into GA4. If you have already used it, you might have noticed something weird..

There is a (not set) dimension in this report.

The (not set) value can obstruct you from understanding where your users came from. It is not always very clear what causes the issue but let’s have a look at the most common ones.

The possible causes of (not set) landing pages in GA4

Generally, (not set) means that the first event for the session was not a pageview or that you have a session with only events and not page views.

This is something you can verify with the help of Explorations. Create a sessions-scoped segment where Landing Page = (not set) and go to User explorer and check the sessions.

But how does this happen in the first place?

There are multiple scenario’s where it might happen. Let’s have a look at them starting with the most frequent cause, session timeouts.

Session timeout and (not set) landing pages

Let’s say you are reading an article on a website. You might Google something in the meantime, make a cup of coffee or get distracted in a different way. Once you hit 30 minutes, by default your session will expire.

Similarly, a user could be visiting the site close to midnight. If the clock ticks past 00:00 hours then the session is ended.

If you then start interacting with the article again by scrolling or clicking to another page, a “new” session is started. And that click or scroll is the first event of the session.

Another cause incorrect setup of tags which leads to events firing before gtm.js.

Incorrect event firing and (not set) landing pages

For example, if a user interacts with the page before accepting cookies, and then accepts, leading to the first page view. Then another (not set) landing page will be registered. You can use the preview mode and check the order of the page load events to determine if this is the case.

Code Implementation Errors

Old on page code could be conflicting with your new GTM code, or if you have an app the property you are using in GA4 might contain both the app data as well as web data. You can verify this by adding a secondary dimension of hostname to you reports.

How can you reduce (not set) landing pages?

• Extend the session timeout if it makes sense for your website. (You can extend this to 7 hours and 55 minutes)
• When you have setup GA4 through GTM, make sure nothing fires before the gtm.js event. I have heard many cases where an incorrect implemented cookie consent banner was the culprit. So be sure to check that.
• Create your own landing pages report or exploration with the “landing page + query string” dimension. This might give you a bit more insight than the standard report.
• For the most analytical flexibilty you can recreate it in BigQuery with the help of a great article of Johan van de Werken

The takeaway

There you have it. Hopefully this is helpful to clear up your landing pages reports. If you would like to learn more about other data hygiene methods, be sure to check out some of our other articles. Good luck!