If you migrated from Universal Analytics to GA4, you have noticed that many of the familiar metrics behave differently. GA4 defines sessions, users, and events in ways that produce numbers that do not match UA — even for the same website over the same period. Understanding these differences helps you interpret GA4 data correctly and avoid drawing wrong conclusions from the new numbers.
How GA4 Defines Sessions
In Universal Analytics, a session timeout occurred after 30 minutes of inactivity. A session could also be split at midnight or when a new campaign source was detected within the same browse.
In GA4, a session is defined by a session_start event and ends after 30 minutes of inactivity. The key differences from UA:
- No midnight session splitting: a GA4 session that starts at 11:45 PM and ends at 12:15 AM is one session. In UA, it would have been split into two (one ending at midnight, one starting at midnight).
- Campaign changes do not split sessions: in UA, if a user arrived via organic search and then clicked a Meta ad in the same 30-minute window, it split into two sessions with different sources. In GA4, it remains one session, and the source is attributed to the first touch of that session.
Result: GA4 typically reports fewer sessions than UA for the same period on the same website. This is not a data quality problem — it is a definitional difference.
How GA4 Defines Users
GA4 uses two user metrics:
Total Users
Any user who triggered at least one event in the date range. This is the broadest count and includes users with a single page view or any interaction.
Active Users
Users who had an engaged session (a session lasting 10 seconds or longer, with 2+ page views, or with a conversion event). GA4 surfaces Active Users as the primary user metric in most reports.
This is a significant change from UA, which showed Total Users (sessions with at least one interaction) rather than Active Users. GA4’s Active Users count is typically lower than UA’s user count for the same period, because it excludes very low-engagement visits.
How GA4 Defines Events
GA4 is an event-based model — every interaction is an event. Page views are events (page_view). Sessions are events (session_start). GA4 does not have separate “hits” and “pageviews” like UA. Instead, every interaction — scroll, click, video play, form submit, purchase — is an event with a name and optional parameters.
This means GA4 event counts are much higher than UA hit counts, because everything is an event. This is expected and does not mean your tracking has gone wrong.
Which Metric Matters Most for Ecommerce
For revenue performance: Purchase Revenue and Transactions
For measuring business outcomes, purchase revenue and transaction count are the primary metrics. These are event-based (purchase events) and are not affected by the session/user definitional differences from UA.
For traffic analysis: Sessions
For understanding traffic volume and source performance, sessions are more useful than users for most analyses. A returning customer who buys twice generates one user record but two sessions with two purchases. Analysing by session better represents actual engagement volume.
For engagement quality: Engaged Sessions and Engagement Rate
GA4’s Engagement Rate (engaged sessions / sessions) is a better quality signal than UA’s Bounce Rate (which was inverse — lower was better). Engagement Rate above 60% generally indicates good content-audience match. GA4’s Bounce Rate is 100% minus Engagement Rate.
For conversion optimisation: Conversion Rate and funnel events
GA4’s User Conversion Rate (users who converted / total users) and Session Conversion Rate (sessions with a conversion / total sessions) are both available. Session Conversion Rate is more comparable to UA’s goal conversion rate.
A Practical Metric Hierarchy for Shopify Stores
For weekly performance review, focus on:
- Purchase Revenue (business outcome)
- Transactions (volume)
- Sessions by source (traffic driver)
- Session Conversion Rate by source (channel quality)
- Average Order Value (revenue efficiency)
Users, engagement rate, and event counts are contextually useful but secondary to these five metrics for most ecommerce performance decisions.
Get Your GA4 Metrics Set Up for Actionable Reporting
GA4 default reports show all metrics but do not highlight which ones matter most for ecommerce. Custom Looker Studio dashboards or GA4 Explorations let you focus on the metrics that are actually relevant to your decisions.
Book your free Shopify tracking audit here and we will confirm your GA4 ecommerce tracking is set up to report the right metrics accurately for your business.