Google Analytics 4 (GA4) was officially launched on Jul 1, 2023. Many companies using the standard version of Universal Analytics (UA) will have noticed the large number of alerts added by Google in the interface, particularly the countdown timer to the official transition date. Companies that did not create a GA4 property by July 1, 2023 were auto-migrated to GA4 using existing site tags.In the first part of our series on GA4, we covered a brief history of Google Analytics along with the inception of GA4 and data privacy laws such as CCPA and GDPR. Those laws propelled the need for reduced reliance on third-party cookies, and GA4 was built to alleviate some of those issues. We also addressed some of the data collection methods that GA4 will be using, along with the partner integrations that marketers can take advantage of and the level of reporting customizations that can be implemented by advertisers to dial down into ad optimization and full-funnel metrics.

In this part of the series on GA4, we are going to address the primary differences in measurement and metrics across UA and GA4. Let’s start by addressing the elephant in the room. What are engaged sessions and why has bounce rate been replaced by engagement rate instead? To address this question, we need to take a step back and understand how GA4 measures events and sessions. In UA, the measurement model was based on a sessions-driven data model that acted as the foundational element to record all interactions or hits during a session. These hits were later categorized as pageviews, events, or ecommerce transactions. Conversely, GA4 uses an events-driven data model that defines all hit types as events (pageviews, scroll depth, clicks, downloads, purchases). A vital difference between these two measurement systems is that GA4 has pre-built events that are automatically added when a GA4 property is created (please review this resource by Google for more details on automatically collected events) and do not require any additional setup in Google Tag Manager or other tag management systems, unlike events in UA that typically require additional code to be set up for more customized events.

Now that you have a basic understanding of the key differences in measurement between UA and GA4, let’s talk about the new metrics that are available to us in GA4. Because GA4 is driven by events, all reports are viewed through the lens of engaged sessions and engagement rate. Google defines engaged sessions as “The number of sessions that lasted longer than 10 seconds, or had a conversion event, or had 2 or more screen or page views.” Instead of looking at all sessions in user and acquisition reports, the focus is to dial into a more qualified segment to help improve decision-making as marketers prioritize channels that are driving more qualified traffic. The engagement rate is the percentage of engaged sessions, which is engaged sessions divided by total sessions. While the overall sessions metric is still available in some reports in GA4, the user acquisition reports are focused solely on engaged sessions to reflect more granularity in terms of user behavior compared to the use of bounce rate in UA. Speaking of bounce rate, is it still available in GA4? Yes and no: you will not find it in any of the standard reports provided by GA4. However, if you choose to customize any of the default reports in the GA4 interface, you do have the option to add it as another metric. Bounce rates in GA4 are the inverse of engagement rates where it measures the percentage of sessions that were not engaged sessions.

We have barely scratched the surface of all the unique and interesting things that GA4 has to offer as we head into a new world of first-party data and consent management. In our next part of the GA4 series, we will touch on commonly used reports in GA4 and how you can create your own custom report using the Explore feature in GA4. 

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