Understanding GA4's Event-Driven Data Model

Google Analytics 4 (GA4) uses an event-driven data model, where every user interaction is captured as an event. This model replaces the older Universal Analytics (UA) structure, which was based on a hierarchical scope system (user, session, hit). In GA4, all interactions—such as pageviews, clicks, transactions, and custom actions—are treated as events, providing greater flexibility in data collection and analysis.

Key aspects of GA4's event-driven model include:

• Events as the core data units: Every user action is an event, including automatically collected events (e.g., page_view, session_start), enhanced measurement events (e.g., scrolls, outbound clicks), recommended events suggested by Google for specific industries, and custom events defined by users to track unique interactions.

• Flexible parameters: Each event can include up to 25 parameters, which add detailed context to the event (e.g., session ID, item category, value). These parameters enable highly customized and granular data collection tailored to business needs.

• Sessions and users are derived from events: Although GA4 does not use a rigid hierarchy like UA, it can simulate session and user-level data by aggregating related events. For example, a session is identified by a "session_start" event, and all events within that session roll up accordingly. Similarly, all events triggered by a user roll up to that user’s profile.

• Simplified event tracking and reporting: GA4 automatically collects many common events, reducing manual setup. Custom events can be sent via tools like Google Tag Manager, and parameters must be registered in GA4 to appear in reports and be usable in custom analyses.

This event-driven approach allows GA4 to provide more detailed, flexible, and cross-platform insights into user behavior, enabling businesses to better understand and optimize user journeys across websites and apps.