The main difference between GA4 vs. Universal Analytics is monitoring hits (a user visiting a website) and how they are labeled and tracked.  Universal Analytics Universal Analytics is session-based and uses hit types such as page hits, event hits, and social interaction hits.  GA4 Google Analytics GA4 Google Analytics is event-based, and hits previously session-based in Universal Analytics are now event-based. Essentially, this means instead of categorizing interactions as page hits or event hits, they are now all counted as events.