The Shift From Sessions to Events: GA4's Core Philosophy
Google Analytics 4 (GA4) is not simply an upgraded version of Universal Analytics (UA) — it's a fundamentally different measurement model. Universal Analytics was built around sessions and pageviews. GA4 is built around events. Everything that happens on your site or app — a page view, a scroll, a button click, a form submission, a video play — is an event.
This shift makes GA4 more flexible and better suited to cross-platform measurement (web + app), but it also means the interface, reports, and data look very different from what UA veterans are used to.
Key Differences at a Glance
| Feature | Universal Analytics | GA4 |
|---|---|---|
| Data model | Session-based | Event-based |
| Cross-platform | Web only | Web + App unified |
| Bounce rate | Yes (standard metric) | Replaced by Engagement Rate |
| Goals | Goals (up to 20 per view) | Conversions (unlimited) |
| Audiences | Basic | Advanced, predictive |
| Data retention | Up to 26 months (free) | Up to 14 months (free) |
| Reporting interface | Pre-built, familiar | More customizable, steeper curve |
| BigQuery export | Paid (360 only) | Free for all users |
What GA4 Does Better
1. Automatic Event Tracking
GA4 automatically collects a range of events without any extra configuration: page views, scrolls (90% depth), outbound link clicks, site search, video engagement (for YouTube embeds), and file downloads. In Universal Analytics, most of these required manual Google Tag Manager setup.
2. Cross-Device and Cross-Platform Identity
GA4 uses a unified identity model that can stitch together user behavior across web and app, or across multiple sessions, using User ID, Google Signals, or device ID. This gives a more complete picture of the customer journey than UA ever could.
3. Predictive Audiences
If your property has sufficient data, GA4 offers machine-learning-powered predictive metrics like purchase probability and churn probability. These can be used to build audiences for remarketing campaigns in Google Ads.
4. Free BigQuery Integration
Exporting raw event data to BigQuery was previously a paid, enterprise feature. In GA4, it's free. This is a significant unlock for marketers who want to run custom SQL queries on their data or build advanced attribution models.
What's Frustrating About GA4
Honesty matters here. GA4 has real limitations and a learning curve that has frustrated many marketers:
- Shorter default data retention: Free GA4 properties retain data for only 14 months by default (compared to 26 months in UA). You must export to BigQuery or Google Sheets for longer retention.
- Sampled data in standard reports: For high-traffic properties, many standard reports use sampled data, which can distort analysis. BigQuery exports give you unsampled data.
- Steeper learning curve: The interface is less intuitive than UA for common tasks like creating funnels or finding basic traffic source reports.
- No historical UA data: GA4 doesn't import historical data from Universal Analytics. Year-over-year comparisons require keeping UA exports or using a data warehouse.
Essential GA4 Setup Checklist for Marketers
- Enable Google Signals for cross-device reporting.
- Set your data retention to 14 months (maximum for free tier) in Admin settings.
- Mark your key actions as Conversions (purchase, lead form submission, sign-up).
- Link GA4 to your Google Ads account for imported conversion tracking.
- Set up BigQuery export — even if you don't use it immediately, historical data starts accumulating.
- Create custom Explorations (funnel, path, segment overlap) for the reports you relied on in UA.
- Configure channel groupings if you use non-standard UTM sources.
Should You Use a Third-Party Analytics Tool Alongside GA4?
Many marketers now use GA4 alongside supplementary tools to cover its gaps:
- Plausible or Fathom: Privacy-first, simple analytics for clean traffic overviews without cookie consent issues.
- Hotjar or Microsoft Clarity: Heatmaps and session recordings that show how users interact with pages, not just whether they converted.
- Looker Studio (formerly Data Studio): Free Google tool for building custom GA4 dashboards that are easier to read than the native interface.
GA4 is the analytical foundation — embrace it, invest time in learning its Exploration reports, and export your raw data to BigQuery from day one. The marketers who master it early will have a significant data advantage.