GA4 vs Universal Analytics - What Actually Changed and Why It Matters

The End of Universal Analytics

On July 1, 2023, Google shut down Universal Analytics (UA). GA4 became the only version of Google Analytics available.

If you are still confused about what changed and why, this article covers exactly that.

The Core Difference: How Data Is Collected

Universal Analytics was built around sessions and pageviews.

Every interaction was categorised as one of a handful of hit types:

Pageview
Event
Transaction
Social
Timing

GA4 is built around events only.

Every single interaction - a pageview, a click, a scroll, a purchase - is an event. There are no separate hit types. Everything is flat.

This sounds like a small technical detail. It is not. It changes how you think about tracking entirely.

Sessions vs Events: Why It Matters

In Universal Analytics, sessions were the primary unit of measurement.

A session grouped all activity from one user visit. Metrics like bounce rate, session duration, and pages per session all came from this session model.

The problem: sessions are arbitrary. A session resets at midnight, after 30 minutes of inactivity, or when a campaign source changes. This created fragmented, inconsistent data.

GA4 shifts focus to events and users.

Instead of asking “how many sessions ended without engagement?”, GA4 asks “did this user engage with the site at all?” - which is a more useful question.

What Stayed the Same

Despite the rebuild, many things carried over:

JavaScript tag still installed via GTM or direct snippet
Integration with Google Ads for audience and conversion sharing
Reporting interface (though redesigned)
Goals → now called Conversions (then renamed to Key Events in 2024)
Audiences for remarketing

The fundamentals of measurement did not change. The architecture did.

Key Changes in GA4

1. Event-Based Data Model

Everything is an event with parameters. A pageview is an event (page_view) with parameters like page_title and page_location.

2. Automatic Event Collection

GA4 automatically collects many events without configuration:

page_view
scroll (90% depth)
click (outbound links)
session_start
first_visit

In Universal Analytics, you had to configure most of these manually.

3. Enhanced Measurement

GA4 has a built-in toggle called Enhanced Measurement that automatically tracks:

Scrolls
Outbound clicks
Site search
Video engagement
File downloads

4. User-Centric Reporting

GA4 uses User ID and Google Signals to track users across devices and sessions more accurately than UA.

5. Explorations

GA4 introduced a new reporting area called Explorations - a flexible workspace for custom analysis that did not exist in UA.

6. BigQuery Integration (Free)

GA4 offers free raw data export to BigQuery. In Universal Analytics, this was a paid feature (GA360 only).

7. No Bounce Rate (Then It Came Back)

GA4 initially removed bounce rate and replaced it with engagement rate - the percentage of sessions that lasted more than 10 seconds, had a conversion, or had 2+ pageviews. Bounce rate was later added back as the inverse of engagement rate.

What Was Removed

View level: UA had Account > Property > View. GA4 has no Views. You manage data streams directly.
Goals: Replaced by Key Events (formerly Conversions).
Custom dimensions at hit level: GA4 uses event-scoped and user-scoped custom dimensions instead.
Behaviour flow: Replaced by the Path Exploration in Explorations.
Real-time reports: Simplified significantly.

Why the Shift Matters for Google Ads Advertisers

GA4 is more tightly integrated with Google Ads than Universal Analytics ever was.

Key reasons this matters:

Key Events feed Google Ads directly. When you mark an event as a Key Event in GA4 and import it into Google Ads, it becomes a conversion action. The data pipeline is cleaner.

GA4 audiences are more powerful. Because GA4 tracks every event, you can build audiences based on any combination of events and parameters - not just pageviews and goal completions.

Attribution modelling is built in. GA4 supports data-driven attribution across all reports, which means you get a more accurate picture of what is actually driving conversions.

Consent Mode integration is native. GA4 was designed with Consent Mode in mind. UA was retrofitted to support it. The difference shows in data quality.

The Mental Model Shift

The biggest adjustment for most marketers is moving from thinking in sessions to thinking in events.

In Universal Analytics:

Did this session convert?
What was the bounce rate?
How many pageviews per session?

In GA4:

Did this user engage?
What events did they trigger before converting?
Which events are most correlated with conversions?

This shift makes GA4 more powerful for analysis - but it requires learning a new way of reading data.

Final Thoughts

GA4 is not Universal Analytics with a new interface. It is a fundamentally different measurement system built for a world with more devices, more privacy requirements, and more complex user journeys.

The learning curve is real. But the capabilities are significantly better.

In the next article of this series, we will cover:

How GA4 collects data - events, parameters, and the data model explained.

GA4 Explorations - How to Build Custom Reports That Actually Answer Business Questions

9 min read

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The GA4 Reports You Actually Need as a Google Ads Advertiser

8 min read

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Setting Up GA4 From Scratch - The Right Way (Property, Data Stream, GTM)