What Is GA4 (Google Analytics 4)?

GA4 vs Universal Analytics

In UA, a purchase was a transaction inside a session tied to a source and medium. In GA4, a purchase is a purchase event with a value parameter, tied to a user across sessions and devices when consent allows. That flexibility is real, but the tradeoff is that GA4 numbers rarely match Shopify or Meta, and reconciling those gaps is the analyst's job in 2026.

Benchmarks

• Session count in GA4 typically runs 10 to 20 percent below UA on the same site.
• GA4 purchase count vs Shopify: expect a 15 to 30 percent gap, mostly cookie-blocked users.
• Data retention default: 2 months for events, 14 months for exploration data. Raise both on day one.

Why it matters

GA4 is the neutral source of truth for cross-channel behaviour. Meta reports Meta favourably; Google reports Google favourably. GA4 reports what actually happened on the site, so long as tagging is complete and consent is honoured. Bad GA4 tagging is the root cause of most CFO-versus-marketer arguments.

Common mistakes

• 1.Leaving default 2-month event retention. You lose year-over-year comparisons.
• 2.Skipping the Purchase event or firing it without value. Revenue reports break.
• 3.Enabling Enhanced Measurement plus manual pageview tags. Every pageview counts twice.
• 4.Trusting Attribution reports without checking Consent Mode setup.

FAQs about GA4

Go deeper

Long-form reads that show GA4 applied end to end.