Google Analytics 4 is the latest and only actively supported version of Google Analytics. Universal Analytics stopped processing new data on July 1, 2023, making GA4 the mandatory platform for anyone tracking website and app analytics through Google's ecosystem. GA4 represents a fundamental shift from the session-based model of Universal Analytics. Everything in GA4 is an event—page views, clicks, scrolls, conversions. This event-based architecture allows more flexible tracking and better handles user journeys that span multiple devices and sessions. The platform uses machine learning to fill data gaps caused by cookie restrictions and ad blockers, which matters more as privacy regulations tighten across Canada and globally. The major differences include: - Event parameters replace custom dimensions in most cases, with more flexibility but a steeper learning curve - Cross-domain and app-to-web tracking work natively without extensive configuration - Predictive metrics like purchase probability come built-in for properties with sufficient traffic - Reports look completely different—exploration reports replace most custom reporting from Universal Analytics - Data retention defaults to 2 months for user-level data unless you manually extend it to 14 months At Ottawa SEO, we migrated our entire 500+ domain portfolio to GA4 in early 2023, months before the deadline. The transition required rebuilding conversion tracking, restructuring event taxonomy, and retraining clients on the new interface. Properties that waited until June 2023 lost historical comparison capability and scrambled to set up basic tracking. The learning curve is real. GA4's interface prioritizes exploration over pre-built reports, which means you need to understand your data structure to extract insights. Budget 20-40 hours to properly configure a commercial site with e-commerce or lead tracking, including setting up custom events, conversions, and audiences. Smaller sites might need 4-8 hours for basic setup plus ongoing refinement as you discover what metrics actually matter for your business decisions.