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GA4 - The Key Changes

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If you utilise Google Analytics as part of your analytics arsenal, you’ll have no doubt heard of the GA4 migration heading your way this year. You’ll probably also have received numerous emails from Google informing you of the change and the dates you need to be aware of over the next 6-18 months.

1st July 2023 - Universal Analytics will cease to record data.

If you’re utilising Google Analytics 360, this will be extended to 1st July 2024. This is a recent extension to provide larger organisations with the migration.

We wrote a comprehensive guide to GA4 a couple of months ago which is worth a read (grab yourself a cuppa first).

However, this post is about the differences between UA and GA4 and how the new platform calculates some of the metrics you’ll be most familiar with. So, let us begin.

We will be covering:

  • Users
  • Pageviews
  • Sessions
  • Bounce rate
  • Event count
  • Traffic sources/acquisitions

The above will likely be familiar to you if you’re used to analysing web traffic. However, if you’re currently migrating to GA4, you may have noticed some discrepancies in your data. Let's find out why.


Metric Universal Analytics GA4 What this means
Total users This is a primary metric of UA and defines the number of total users. Counts the number of unique users who logged an event. Expect a drop in traffic as GA4 focuses on engagement rather than just visits.
New users This is the number of users who interacted with your site for the first time. The number of users who interacted with your site or launched your app for the first time. This is measured using a new unique user ID. This number could include both app and web traffic.

This use of user IDs will improve the accuracy of your user data.
Active users Not currently available. This is a primary metric of GA4 and defines an active user who has engaged with your app or website. The engagement time can be set as required - the default is 10 seconds. This metric places quality over quantity, which means you may see lower figures than historically reported as users in UA.


Metric Universal Analytics GA4 What this means
Pageviews Total number of pages viewed. Should a user refresh and view the same page, this would also be counted. Known as ‘views’, this metric measures the number of app screens or web pages your users viewed. Repeated views or web pages are counted. If you are tracking a web and mobile application, this should be taken into consideration when analysing the data.

UA allows for additional filtering options not supported by GA4, which may cause discrepancies between the two metrics.
Unique Pageviews This is the total number of web pages viewed but duplicates are not counted. No longer measured.


Metric Universal Analytics GA4 What this means
Session This is defined as the length of time a user is engaged with your website or app.

Parameters can be set to determine when a new session would start, e.g. after 30 minutes of inactivity or after midnight.

If a user returns after the session has expired, a new session will be started.

If a user is on the website and activity occurs past midnight, a new session will start.

New campaign parameters can create a new session.
This is defined as session start, i.e. when a page or app has been opened and no current session exists.

A session will end after 30 minutes of inactivity unless you customise the parameters.

Sessions are not restarted after midnight or when new campaign parameters are activated.

If a user comes back to your website or app after a session timeout, a new one will automatically begin.
Your number of sessions may drop depending on the settings you have implemented for GA4.

This has the potential to have greater impact depending on the campaign parameters you have set.

If you used a number of UTM tags in Universal Analytics, you should expect to see a lower count of sessions in GA4.

Filters will impact data as GA4 does not support existing filters.

Bounce Rate

Metric Universal Analytics GA4 What this means
Bounce Rate This is the percentage of single page sessions where no activity has taken place.

If your user visits your website but doesn’t engage, such as by clicking on a link or triggering an event and then leaving, this would be counted as a bounce.
This is the percentage of sessions which were not defined as engaged.

If a user visits your website or app for less than 10 seconds without an engagement, this would count as a bounce.

An engaged session is a session that lasts 10 seconds or longer, has 1 or more conversion events, or has 2 or more page or screen views.
This is quite a change. Bounce rate is now a measurement of users who did not engage with your website or app.

It is the percentage of unengaged users.

This approach should have more value, particularly for single page applications or news website where a user only visits one page.

Event Count

Metric Universal Analytics GA4 What this means
Total events An event has several attributes, such as a category, action, label and a hit type (such as a page view or an interaction).

Events can be set up to track specific interactions, which then increments the total events value every time the event is triggered
GA4 does not track a total events value but rather an individual event count. Depending on your current UA setup, an event may be the same within GA4. For example, a contact form event may only occur on one page which means the event would only fire on one form.

However, if you have several contact forms across your website, this would have been tracked as multiple events in UA. In GA4, it will be one event with different parameters (such as the page).
Event Count UA tracks total events rather than individual event counts. Events are tracked for every hit and do not use the category, action or label attributes found in UA.

All actions fired are now events. Unlike in UA, they do not have unique names and, as such, can be reused but with different parameters being applied.

For example, firing an event on a button which repeats across a website would use the same event - but a parameter may refer to the page where the button was clicked. In UA, this would require a unique event for each button instance.
Because of this, event counts between UA and GA4 may change drastically upon comparison.

Because of the changes regarding categories, actions and labels, it’s best-practice to remap event data collection, as opposed to directly migrating your existing structure over to GA4.

Traffic sources/acquisitions

Metric Universal Analytics GA4 What this means
Session/traffic-based acquisition metrics Displays channels or sources of users and sessions. This displays channel and medium source data against metrics, such as users or sessions. This is more around users, sessions and the differences highlighted above.

Otherwise, no real change.

This is a summary of some of the potential causes for data discrepancies. It’s important to note that, if you’ve changed your consent initialisation as part of the migration, this also has the potential to cause discrepancies in your data.

Still not got to the bottom of your data discrepancies?
Get in touch today to find out how we can help.
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