Metric and calculation changes in UA vs. GA4A fundamental area of confusion for Google Analytics users transitioning from UA to GA4 is that GA4 uses different metrics and calculations than UA. It lets you reuse Google Analytics audiences as retargeting audiences in Google Ads (thus, you can show more targeted ads to them). Data sampling in GA4While it isn’t new or unique to GA4, data sampling is another factor frequently confusing users. Similarly, while some UA accounts are still recording data, Google is sunsetting UA, and eventually, you'll be missing data there. You won’t have GA4 data before it is installed on your site.