Google Analytics – Why Is My Performance Down in GA4 Compared to Universal Analytics?

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As Google Analytics phases out Universal Analytics (UA) and pushes users to use Google Analytics 4 (GA4), you may now be looking at your performance and stats in the new GA4. But why are there data discrepancies between GA4 and UA, and should you be worried? The answer is ‘no’, as you’ll be ultimately getting more accurate data. Read on to find out more.

How Do GA4 & UA Measure Users?

Firstly, it’s important to look at how GA4 and UA measure the number of users on your website.

UA gets data from cookie tracking. A website with UA sends a cookie into the user’s web browser which allows it to monitor web activity. UA uses a session based data model.

However, GA uses first party data as well as a Google signal from users who opt out of personalised ads – this is because more and more people are opting out of cookies for GDPR purposes. GA4 uses an event-based data model.

Now that we understand how GA4 and UA collect data, we can look at why there might be differences in the data collected.

Why Does My GA4 Data & UA Data Not Match?

We’ve been running some of our client’s GA4 and UA accounts in parallel – as recommended to ensure collection of data. However, when comparing data from both accounts, we’ve noticed that there were some differences and the metrics didn’t quite match. Below we look at different factors that may result in your GA4 and UA data not matching.

Missing Events

As mentioned above, GA4 uses an event-based data model. This means that it does not use goals – unlike UA – so you cannot directly translate UA goals into GA4, which could result in a change of data.

Bot Filtering

In your UA settings, you can manually exclude all hits from known bots and spiders, but if this checkbox is unchecked, it may mean that your UA account is tracking bot activity. However, GA4 automatically excludes bots, meaning your data might be lower in GA4 than UA – but it means that it is more accurate for tracking your users and target audience.

Cookie Blockers

You may be losing data through cookie blockers on certain browsers like Safari. Third party cookies especially may not work well with some browsers. Privacy settings blocking Google Analytics or Google Tag Manager can therefore result in your data not being the same across the two data collection techniques.

Different Time Settings

If a user is browsing your website between 11:59pm and 12:01am, UA counts this as two traffic sessions – but GA4 counts this as one session. What’s more, UA only counts one conversion per session for each goal, but GA4 counts every event.

Both of these reasons could result in GA4 data not being as high as UA data counts.


In UA, data is sorted into sessions – a group of user interactions on your website over a period of time. During this session, analytics collects and stores interactions. In GA4, analytics collects and stores interactions as events. These provide insight on what’s happening on both your website and app. Events include information that specifies the action taken (page visited, value of purchase, clicks etc). This means that sessions and events will be slightly different.

What’s more, UA counts only one conversion per session, whilst GA4 counts every conversion event even if it is recorded multiple times.


UA has two user metrics – total and new users. GA4 has both of those plus active users. UA refers to total users, GA4 refers to active users. This means that looking at the ‘user’ section will not include everything that you need.


Ultimately, GA4 tracks data more accurately, which is a positive thing for your business and reporting.

Whilst UA wont stop collecting new data until July 2023, we strongly recommend that you set up GA4 as soon as possible which will allow you to collect data in the meantime. What’s more, you can’t backfill a GA4 property with historical data, so it’s best to start collecting now, it can take some time for GA4 to collect and process the data. You can run them simultaneously with UA – meaning you can then still do year on year comparisons.

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Rebecca helps to keep the team organised and supports all of our clients with day to day activities and content. She also runs all of Ballyhoo's internal marketing.