Seeing a lot of ‘not set’ traffic in GA4? Here’s how to fix it
Do you regularly see “not set” appearing in your GA4 reports? This is not just an error message. It is a sign that something is structurally wrong with your tracking or tagging setup. GA4 does register traffic, but it does not know where it comes from. That means you lose critical insights, which directly impacts your marketing decisions.
What does ‘not set’ mean in GA4?
The “not set” value appears when a dimension such as source, medium, or landing page has not received a value.
This often happens when the tracking configuration is not set up correctly. Common causes include:
- The use of Single Page Applications (SPAs), where page changes are not automatically recognised as new sessions
- Incorrect tag loading order in Google Tag Manager
- Missing parameters such as UTM tags or a referrer
Prevent data loss and inaccurate insights with smarter tagging, tracking, and consent settings
5 practical solutions
- Ensure the correct tag order in GTM
The Google tag should load first, except for the consent mode tag. If other tags fire earlier, session data may be lost before GA4 can capture it. - Use a separate tag for page_view events
Do not send the page_view event from the default GA4 tag. Instead, create a separate tag for it. This gives you better insight into when a page is actually loaded and helps prevent measurement errors. - Correctly connect Google Ads to GA4
Make sure your Google Ads account is linked to GA4. Without this connection, GA4 misses essential campaign data, which can lead to “not set” values in your acquisition reports. - Implement consent mode correctly
Cookie consent must be processed correctly on every page before tags are triggered. If this does not happen, data collection may be blocked, resulting in incomplete session data. You can easily verify this in the Google Tag Manager debugger under the “Consent” tab. - Check your UTM tagging
Incomplete or incorrect UTM parameters remain one of the biggest causes of “not set”. Make sure every campaign URL includes at least a correct utm_source, utm_medium, and utm_campaign.
The result: reliable data and better decisions
These optimisations improve the reliability of your data, ensure sessions are assigned to the correct channels, and give you a clearer understanding of what actually works. That way, you make informed decisions based on data you can trust.