What to expect when comparing metrics between Google Analytics 4 and Universal Analytics – it’s quite a difference in behavior and it will take a little bit of time to get used to GA4.
In Universal Analytics, there are two User metrics: Total Users, and New Users.
In Google Analytics 4, there are three User metrics: Total Users, Active Users, and New Users.
Keep in mind
Universal Analytics highlights Total Users (shown as Users) in most reports, whereas GA4 focuses on Active Users (also shown as Users). So, while the term Users appears the same, the calculation for this metric is different between UA and GA4 since UA is using Total Users and GA4 is using Active Users.
Depending on how frequently your users return to your website, the Total Users metric in UA and the Active Users metric in GA4 may be more or less similar.
You can compare Total Users from UA to Total Users in GA4 by using Explorations in GA4 to find your total users number. These numbers may be more comparable than the Users metrics in the GA4 reports due to the differences in definitions.
UA and GA4 use different user-identity methods; UA uses Client ID while GA4 uses User-ID.
Your UA reports may be excluding data based on filters. GA4 properties currently do not support these filters.
In general, Pageviews should be fairly close between UA and GA4, generally within a few percentage points, since the global site tag fires on each page and generates a pageview. However, the differences can vary based on any filters you may have set up in Universal Analytics or Google Analytics 4.
Keep in mind
Universal Analytics tracks screenviews in separate mobile-specific properties, whereas GA4 combines both web and app data in the same property. If you are tracking both web and app data in your GA4 property, be sure to take the additional app traffic into consideration when comparing pageview metrics between the two.
Universal Analytics allows for additional filtering options which may impact the data contained in the view you are comparing to. For example, if you use a filter to exclude certain geographic regions, then your pageview counts between UA and GA4 may differ more.
Google Analytics 4 properties currently do not support filters, while data in Universal Analytics reporting may be subject to view filters that exclude data. For example, both UA and GA4 offer the ability to filter out internal IP traffic and unwanted referrals, but UA may have additional filters applied. When you are comparing, be sure that you have the same filters in place for both properties.
Web purchase counts should match closely. We never expect all events to be collected perfectly, and purchase events are no exception to that rule, however these events are atomic and critical so event counts should match closely across UA/GA4.
Be sure you are collecting a unique transaction_id value in both UA and GA4 to ensure you are comparing similar metrics.
Keep in mind
The transaction_id parameter, if not consistently and properly applied, could create noticeable differences when comparing data. For data quality and comparison purposes, ensure that this data is collected consistently as per the documentation.
Be sure to use all of the required parameters for GA4 ecommerce implementation (as well as for UA) to ensure that ecommerce data is recorded properly.
More focus on session_start event.
Keep in mind
The difference in session count between UA and GA4 can vary from business to business depending on several factors, including:
- Geography – consider the timezones of your users and how likely they are to cross the midnight threshold to restart a session. This is especially relevant if you have a global customer base.
- Use of UTMs on owned websites or apps. Using UTM tagging on your own website is not recommended since it will reset the session in Universal Analytics. If you do use UTMs on your own website, you may see a much higher count of sessions in UA than in GA4.
- Use of filters. Google Analytics 4 properties currently do not support filters, while data in Universal Analytics reporting may be subject to view filters that exclude data.
Session/Traffic based Acquisition metrics
Note that the main differences you may see between UA and GA4 for acquisition metrics are aligned with the differences you will see for the metrics of Users or Sessions
Keep in mind
Since Sessions and Users are the main metrics of comparison for acquisition metrics, refer to the Sessions and Users sections in this article.
If your conversions are based on destination URLs or on UA (i.e. Category/Action/Label) events for which you have set up equivalent GA4 conversion events, Conversions can be quite close. However, there are important differences between UA and GA4 that may make it difficult to compare conversion counts.
You define a goal to indicate that a particular user action is to be considered a conversion. For example, if you define a “Form Submit” goal, a conversion will be registered each time a user submits the form.
UA counts only one conversion per session for each goal. So, if a user submits the form twice during the same session, only one conversion will be counted for the “Form Submit” goal.
You specify a conversion event for each action that you want to count as a conversion. For example, if you specify that the “Form Submit” event is a conversion event, a conversion will be registered each time a user submits the form.
GA4 counts every instance of the conversion event, even if the same conversion event is recorded multiple times during the same session. So, if a user submits the form twice during the same session, two conversions will be counted.
Keep in mind
Universal Analytics supports five goal types: destination, duration, pages/session, smart goals, and event goals. GA4, in contrast, only supports conversion events. It may not always be possible to use GA4 conversion events to precisely duplicate some UA goal types. For example, it’s not possible to duplicate a smart or duration goal using GA4 conversion events.
UA counts only one conversion per session, for the same goal. GA4 counts multiple conversions per session, for the same conversion event.
Bounce Rate vs Engagement Rate
Only in UA: Percentage of single page sessions in which there was no interaction with the page. A bounced session has a duration of 0 seconds. For example, if a user comes to your website and reviews the content on the homepage for several minutes, but leaves without clicking on any links or triggering any events being recorded as interaction events, then the session will count as a bounce.
Only in GA4: Percentage of Engaged Sessions. Engaged Sessions is the number of sessions that lasted longer than 10 seconds, had a conversion event, or had at least 2 pageviews or screenviews.
Keep in mind
Bounce Rate was a reasonable measure of site engagement at one time, but has become less useful as websites and apps have changed. For example, it’s possible for users to view a single page app and leave without triggering an event, which would be considered a bounce. GA4 uses metrics that are more relevant to how websites and apps work today.
Because Engagement Rate has a time threshold associated with it, it cannot be considered the inverse of Bounce Rate.
Events represent a fundamental data model difference between Universal Analytics and Google Analytics 4 properties.
A Universal Analytics event has a Category, Action, and Label and is its own hit type.
For example, an event can be set up to register that a sign-up button has been clicked. The event might have a Category of “CTA”, an Action of “Sign Up”, and a Label that is the destination URL.
Total Events increments each time a Category/Action/Label event is triggered.
Every “hit” is an event and GA4 events have no notion of Category, Action, or Label. For example, when someone views one of your website pages, a page_view event is triggered.
All actions are events. Each event name is not necessarily unique (in fact, it’s best practice to reuse the same event name many times, differentiating the event by the parameter values collected). For example, a sign-up might have an event name of sign_up with parameters page_location, product, form_id, and so on. The same event name could (and should) be used on every sign up button across the site (whereas in UA, you would want to use unique event naming for each button).
Keep in mind
In GA4, the sign_up event may or may not mean the same thing as in UA. If your website only has one signup form and only one button where the sign up event would fire, then these event counts may be quite close. However, if your website has multiple sign_up events, then comparing the event count between GA4 and UA may not be as straightforward and the numbers may not be close.
GA4 reports do not display Category, Action, and Label. It’s better to rethink your data collection in terms of the GA4 model rather than port your existing event structure to Google Analytics 4.