Comparing the data
There are some crucial differences in how data is handled and output by GA4 compared to UA
Users One particularly prominent difference is how Google Analytics 4 handles Users. Both Universal Analytics and Google Analytics 4 report on the number of Users on the site, but that means something very different for each of them; which can lead to confusion.Read Google's Support Documents Metric UA GA4 Total Users
Primary user Metric
Total number of users
Total number of unique users who logged an event New UsersNumber of users who interacted
with your site for the first time
Number of users who interacted with your site of launched your app for the
first time. The Metric is measured by the number of new, unique, user IDs
that logged the "first open" or "first visit" event.
Active Users N/ANumber of distinct users who visited your website or application. An active
user is any user who has an engaged session or when Analytics collects the
"first visit" event or "engagement time msec" parameter from a website.
A lot of reporting in UA was based on Total Users and New Users, but you simply can't do the same in GA4. Essentially in the new system, a user is only counted if they accept the cookies prompt and interact with the site in a meaningful way. With this in mind, it is quite probably that a large proportion of the 'users' being tracked in UA were not actually users, but most likely bots that never pass the Cookie prompt. More on Cookies and their impact on Analytics below.
How are you getting Cookie consent?
There are a couple of options when it comes to prompting users to accept cookies.
Cookies Since the introduction of GDPR regulations in 2018, it is a requirement that users can consent to or decline being tracked via Cookies on a website. As Universal Analytics predated these changes, GA4 has essentially overhauled how users are handled based on their cookie acceptance. Bottom line: for users who do not accept cookies, GA4 will not be able to deliver accurate data - especially for metrics like conversions and revenue. Additional comparisons between data in UA and GA4Posted by Iconography Ltd