Universal Analytics stopped processing data on July 1, 2024. GA4 is now the only version of Google Analytics available. But if you migrated without fully understanding how GA4 differs from what came before, your reports may be misleading you — and your ad decisions may be built on numbers that look right but are not comparable to your history.
This guide covers the most important differences between GA4 and Universal Analytics, and what they mean for your Shopify store and ad campaigns.
The Core Difference: Events vs Sessions
In Universal Analytics, everything was session-based. A session grouped all user activity in a single visit, and goals were triggered when something happened inside that session.
In GA4, everything is an event. A session start is an event. A page view is an event. A purchase is an event. There are no goals — only conversions, which are events you mark as important in GA4 Admin.
This changes how data is structured, how it is queried in BigQuery, and how you set up conversion tracking. The concepts carry the same names in some cases but measure different things.
Sessions Still Exist in GA4 — But They Work Differently
GA4 still counts sessions, but calculates them differently:
- In UA, a session reset at midnight or when the utm campaign changed
- In GA4, a session ends after 30 minutes of inactivity, or when a campaign parameter changes
- Midnight does not reset a GA4 session
This means GA4 session counts are often lower than UA session counts for the same period, even when traffic levels are identical. Do not try to benchmark your GA4 session numbers against old UA data. They are not the same metric.
How Ecommerce Tracking Changed
UA used a separate Enhanced Ecommerce plugin with its own dataLayer push structure. GA4 tracks ecommerce through standard events with a specific parameters structure. The core events are:
- view_item — user views a product
- add_to_cart — user adds to cart
- begin_checkout — user starts checkout
- purchase — user completes an order
Each event sends an items array with product details (name, ID, price, quantity, category). If the items array is missing or malformed, product-level data will not appear in your GA4 ecommerce reports even though the purchase event itself may be recording.
Shopify natively sends all these events — but Shopify’s 2024 checkout extensibility update changed when and how the purchase event fires, and many stores lost purchase tracking without realising it.
Goals vs Conversions
In UA, you had up to 20 goals per property. In GA4, any event can be marked as a conversion with no hard limit.
Important difference in how they count: in UA, a goal only counted once per session even if the user triggered it multiple times. In GA4, a conversion counts every time the event fires. If your Shopify thank you page fires the purchase event twice (a common issue when customers refresh the confirmation page), GA4 will count two purchases for one order.
Cross-Device Tracking
GA4 supports three identity methods that UA did not have by default:
- User ID — your own ID for logged-in customers, stitches sessions across devices
- Google Signals — aggregated cross-device data from signed-in Google users (requires consent)
- Device ID — the client ID from the cookie, same as UA’s standard tracking
GA4 combines all three to give a more complete picture of multi-device customer journeys. UA could only track by client ID unless you explicitly implemented User ID.
Reporting Differences
UA had a fixed set of reports you navigated by category. GA4 has standard reports, but most of the analytical power lives in the Explore section, where you build custom analyses using Funnel Exploration, Path Exploration, Segment Overlap, and Cohort Analysis.
The tradeoff: GA4 standard reports are less intuitive for many marketers who are used to UA. The data is all there — you just need to know where to look, and when to build a custom Exploration instead of relying on the default views.
Metrics That Are Not Directly Comparable
Do not compare these metrics between GA4 and UA — they are measuring different things:
- Bounce rate: UA = single-page sessions; GA4 = sessions with no engagement (under 10 seconds, no events, no second page). GA4 bounce rates are typically much lower for the same traffic.
- Sessions: GA4 counts fewer sessions than UA for identical traffic due to the midnight reset difference
- New users: GA4 identifies new users more conservatively (device ID vs cookie reset)
Any year-over-year comparison you make for 2024 that spans the UA-to-GA4 cutoff will show anomalies. This is expected — the metrics changed, not the business.
What This Means for Your Shopify Tracking Today
If you migrated from UA to GA4 when UA was shut down, your tracking may have been copied without being adapted for GA4’s event model. Many stores still have configurations designed for UA-style dataLayer pushes that no longer map correctly to GA4’s required parameters.
The result: GA4 reports that look reasonable on the surface, but with missing revenue data, zero item detail in ecommerce reports, or duplicate purchase events counting orders twice.
Make Sure Your GA4 Setup Is Actually Accurate
GA4 is more capable than Universal Analytics — but only when it is set up correctly for the event-based model. If you are not sure whether your Shopify store is capturing all purchases with the right parameters, a tracking audit will tell you exactly what is wrong.
Book your free Shopify tracking audit here. We check every GA4 event, verify your ecommerce setup, and give you a clear list of what needs to be fixed.