Full Definition
Google Analytics 4 (GA4) is Google's current analytics platform, which replaced the long-running Universal Analytics (UA) in July 2023. It represents a fundamental rethinking of how user behaviour is tracked — moving from a session-based model to an event-based model.
Key differences from Universal Analytics:
**Event-based tracking**: In UA, a page view was the core unit. In GA4, everything is an event — page views, button clicks, video plays, scroll depth, form submissions, purchases. This makes GA4 far more flexible and granular.
**Cross-device measurement**: GA4 can stitch together a user's journey across devices (mobile visit on Tuesday, desktop purchase on Thursday) using a combination of Google accounts and machine learning. UA couldn't do this reliably.
**Privacy-forward design**: GA4 was built for a world without third-party cookies. It uses modelled data to fill gaps where tracking consent is not given — giving you more complete reports than a cookie-dependent system.
**Predictive audiences**: GA4's machine learning can predict which users are likely to purchase or churn — letting you build custom audiences for Google Ads remarketing based on predicted behaviour, not just past behaviour.
**Exploration reports**: Custom funnel reports, path exploration, and user explorer tools that were premium features in UA are standard in GA4.
For SMBs, setting up GA4 correctly from the start is critical: define your Key Events (what counts as a conversion), link it to Google Ads, link it to Google Search Console, and enable enhanced measurement.
Actionable tip: In GA4, navigate to Reports > Acquisition > Traffic Acquisition and add a secondary dimension of 'Landing Page.' This shows you which specific pages visitors first arrive on, from which sources — one of the most actionable views for identifying SEO and ad performance.