What is the difference between Google Analytics 4 (GA4) and Universal Analytics (UA)?

GA4 uses an event-based tracking model, allowing detailed and customizable tracking of user actions (e.g., clicks, scrolls) across websites and apps, unlike UA’s session-based, hit-driven model focused on pageviews. GA4 offers deeper insights, cross-platform tracking, and advanced audience segmentation, but requires setup adjustments as UA stopped processing data by July 2025.