This article is part of the Universal Analytics to Google Analytics 4 migration guide. See the migration guide table of contents.

[UA→GA4] Comparing metrics: Google Analytics 4 vs Universal Analytics

What to expect when comparing metrics between Google Analytics 4 and Universal Analytics

As you set up Google Analytics 4, you may want to compare the reported results in your Google Analytics 4 property against those in your Universal Analytics property. This article explains the extent to which you can and cannot compare metrics between Universal Analytics and Google Analytics 4.

In this article:

Users

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

Metric

UA

GA4

Total Users 

Primary user metric in UA: Total number of users

Total number of users

New Users 

Number of users who interacted with your site for the first time

Number of users who interacted with your site or launched your app for the first time, and is triggered by the first_open event

Active Users

N/A

Primary user metric in GA4: Number of users that have been active within a 28 day time period

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.

The two types of properties could be using different settings, such as user-identity spaces; for example, the Google Analytics 4 property might be using User-ID while the Universal Analytics property is using Client ID.

Your UA reports may be excluding data based on filters. GA4 properties currently do not support these filters.

Pageviews

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. 

Metric

UA

GA4

Pageview

Total number of pages viewed. Repeated views of a single page are counted.

aka Views: Total number of app screens and/or web pages your users saw. (The Views metric found in the reporting interface is the combination of pageviews and screenviews.) Repeated views of a single screen or page are counted.

Unique Pageview

Total number of pages viewed but duplicates are not counted

N/A

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.

Purchases

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. 

 

Metric

UA

GA4

Purchases

  • purchase events are fired within the Enhanced Ecommerce model
  • Data is pulled from a products array via Google Analytics-provided JavaScript and collected in a purchase event when you choose to send that event
  • purchase events are recommended and collect data in a similar fashion to UA, but there are differences
  • Does not provide additional JavaScript for array collection and expects you to provide the items array when collecting a purchase event on your own (though the same advice is given with regard to populating a data layer object)

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.

Sessions

Metric

UA

GA4

Session

  • Period of time a user is actively engaged with your website or app
  • Has defined parameters for what may cause it to end e.g. a session will end when there has been more than a 30-minute period of inactivity (depending on the session timeout settings), the timestamp has been cut off at midnight (according to the timezone the view is set up in), or new campaign parameters are encountered. 
  • If a user comes back after a session timeout, it will start a new session
  • If the user is on the website when midnight arrives, a new session will be started
  • If a user picks up new campaign parameters while on the website, a new session will be started

aka Session Start

  • To determine the session that each event comes from, the session_start event generates a session ID and Analytics associates the session ID with each subsequent event in the session
  • A session will end when there has been more than a 30-minute period of inactivity (depending on the session timeout settings)
  • Sessions are not restarted at midnight or when new campaign parameters are encountered
  • If a user comes back after a session timeout, it will start a new session

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.
  • Filters - The data in UA reporting may be subject to view filters that exclude data. The data in GA4 reporting for Google Analytics 360 customers may be subject to filters that define which data from a source property appears in a subproperty. However, Google Analytics still generates a session ID when you filter out the session_start event from a subproperty.
  • Estimation - Google Analytics 4 properties use a statistical estimate of the number of sessions that occurred on your website or app by estimating the number of unique session IDs, while Universal Analytics properties don't estimate the number of sessions. The estimates used by Google Analytics 4 properties more efficiently count sessions with high accuracy and low error rate.

Session/Traffic based Acquisition metrics

Metric

UA

GA4

Session/Traffic based Acquisition metrics

Found in the Acquisition section in a number of different reports, such as the Channels report or the Source/Medium report

Channel or Source/Medium is the dimension being analyzed against metrics such as Users and Sessions

Traffic acquisition metrics can be found in the Traffic Acquisition report

The dimensions of Channel or Source/Medium are measured against metrics such as Users and Sessions

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.

Conversions

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.

Metric

UA

GA4

Conversions

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

Metric

UA

GA4

Bounce Rate

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. N/A

Engagement Rate

N/A

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.

Event count

Events represent a fundamental data model difference between Universal Analytics and Google Analytics 4 properties.

Metric

UA

GA4

Total Events

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.

N/A

Event count

N/A

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.

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