Google Analytics 4 launched in October 2020, initially branded as "Google Analytics 4 properties" to differentiate it from Universal Analytics. Google pushed GA4 hard between 2020 and 2023, eventually forcing migration by sunsetting Universal Analytics on July 1, 2023 for standard properties and October 1, 2023 for Analytics 360 accounts. The shift wasn't just a version bump. GA4 replaced session-based tracking with event-based measurement, unified web and app data in one property, and leaned heavily into machine learning for predictive metrics. Many SEO teams and agencies, including ours, found the transition painful because GA4 threw out familiar reports like bounce rate (replacing it with engagement rate) and completely restructured the interface. Why the forced timeline mattered: Google stopped processing new data in Universal Analytics after July 2023, meaning anyone who delayed migration lost historical tracking continuity. We migrated our 500+ domain portfolio between late 2022 and early 2023, running both properties in parallel for months to preserve year-over-year comparisons. Key differences that caught people off guard: - Event parameters replaced custom dimensions in most cases - Conversions became event-based rather than goal-based - Reports shifted from pre-built tables to customizable exploration tools - Data retention defaults to 2 months unless manually extended to 14 months - BigQuery integration became free for all properties, not just 360 For Canadian agencies and businesses, the 2023 deadline meant scrambling to retrain teams, rebuild dashboards, and reconfigure conversion tracking mid-year. At Ottawa SEO, we treat GA4 setup as mandatory infrastructure now, not optional. If you're still clinging to old Universal Analytics data exports, understand that Google isn't bringing that interface back. The October 2020 launch gave everyone nearly three years of runway, but most businesses waited until the last six months to take it seriously.