Google Analytics 4 is the mandatory replacement for Universal Analytics, built from the ground up to handle cross-platform tracking and survive the decline of third-party cookies. Instead of organizing data around sessions and pageviews like the old system, GA4 treats everything as an event—scroll depth, video plays, form submissions, pageviews, all structured the same way. This makes custom tracking more flexible but also means the interface and reports look completely different from what most people used for a decade. GA4 leans heavily on machine learning to fill gaps where user tracking is blocked or incomplete. It generates predictive metrics like purchase probability and churn probability based on patterns in your data, though these require minimum traffic thresholds to activate. The platform also introduced BigQuery integration on the free tier, which is huge for anyone doing serious analysis or building custom dashboards—previously that cost thousands monthly. The privacy angle matters more every year. GA4 was designed for a world where GDPR, CCPA, and browser restrictions limit what you can track. It uses Google's own modeling to estimate conversions that can't be directly measured, and it supports cookieless measurement through Google signals when users are logged into Google accounts. That said, you still need proper cookie consent flows in Canada and the EU, and GA4's default setup often undercounts compared to UA. At Ottawa SEO, we migrated all 500+ domains before the July 2023 deadline, and the learning curve was real. The reports are less intuitive out of the box—you'll spend time building custom explorations instead of just opening a prebuilt report. Event tracking requires more upfront planning, especially if you want to track form submissions, file downloads, or outbound clicks properly. We typically set up enhanced measurement, configure key events (conversions), and connect Search Console and Google Ads on day one. If you're running any paid campaigns or doing serious conversion optimization, getting GA4 configured correctly isn't optional anymore—there's no fallback.