Why does GA4 show different numbers from Universal Analytics?

Because the measurement model changed. GA4 counts events instead of sessions and pageviews, applies different session timeout and attribution rules, and uses data thresholds and modelling. The numbers are not directly comparable, so rebuild benchmarks instead of trying to reconcile them.

What should I set up first in GA4?

Conversion events tied to real business actions, then Google Ads linking, then enhanced measurement checks so you know what is being tracked automatically. Without properly defined key events, everything downstream, including automated bidding, learns from the wrong signal.

Analytics

GA4 (Google Analytics 4)

GA4 is the current version of Google Analytics, built around an event-based model that tracks user interactions across web and apps.

It replaced Universal Analytics in 2023 and changed core metrics, for example using engagement rate rather than the old bounce rate. It provides flexible reporting, cross-platform tracking, and integration with Google Ads. Setting it up correctly is the foundation of measuring marketing performance.

The default configuration collects less useful data than most teams assume, and the gaps are quiet. Key events have to be defined deliberately, cross-domain tracking needs configuring if forms or checkout sit on another domain, and internal traffic filters are off until someone turns them on. Data retention defaults to a shorter window than most reporting needs, and extending it does not apply retroactively, so the months before someone notices are gone. A short configuration review when the property is created prevents a year of analysis built on data that was never being collected properly.

Example

A team defines one key event, generate_lead, links Google Ads, and turns retention to 14 months. Six months later they can answer: which campaigns produce leads that arrive at 40% less cost from mobile, and what share of organic visitors convert within 30 days. The neighbouring account that kept defaults can answer none of it: the data was never collected, and no setting applies backwards.

Frequently asked questions

Why does GA4 show different numbers from Universal Analytics?: Because the measurement model changed. GA4 counts events instead of sessions and pageviews, applies different session timeout and attribution rules, and uses data thresholds and modelling. The numbers are not directly comparable, so rebuild benchmarks instead of trying to reconcile them.
What should I set up first in GA4?: Conversion events tied to real business actions, then Google Ads linking, then enhanced measurement checks so you know what is being tracked automatically. Without properly defined key events, everything downstream, including automated bidding, learns from the wrong signal.

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GA4 (Google Analytics 4)

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