Answer:
Not everyone is eligible for remarketing: some GA4 users won’t be included in Google Ads audiences. This could be due to privacy settings, missing cookies, or users opting out of ads.
- Data syncing delays: usually, there’s a lag between GA4 and Google Ads syncing data, so audience sizes might not match up perfectly.
- Different rules for audience size: GA4 and Google Ads have slightly different ways of counting audiences. Plus Google Ads requires a minimum number of users before an audience can be used in your campaigns, which might exclude smaller groups.
- 1st-Party vs. 3rd-party data: GA4 uses 1st-party data to capture a wider range of users. But Google Ads relies on 3rd-party cookies, so if someone rejects marketing cookies or turns off personalized ads, they won’t show up in your Google Ads audiences.