Have you ever wondered why your Google Analytics 4 (GA4) conversions are lower compared to Universal Analytics (UA) after the shift in July 2023? As GA4 has replaced the widely used UA, it was said that GA4 is capable of bringing a range of advanced features and improved tracking capabilities to help businesses gain deeper insights into their online performance, especially conversions. However, there is a problem that most advertisers are facing: “Why do the data on GA4, UA, and Google Ads not line up?” This platform which was deemed to be an enhanced version of advancement in analytics technology has brought many advertisers the issue of conversion discrepancies between UA and GA4. An advertiser also pointed out that their account is experiencing up to a 50% decrease in GA4 for some events, including e-commerce conversions. However, all settings have been thoroughly tested and verified.

In this article, we will provide an overview of the conversion discrepancy issue between UA and GA4 as well as discuss some common reasons for the discrepancy. We can also gain a better understanding of data discrepancies not only between Google Analytics (GA) but also Google Ads.

Let’s take this account as an example. In GA4, the purchase conversions are 193 while UA is 106. However, after importing the goals into Google Ads, it was observed that the conversion numbers of UA (90.36) are significantly higher compared to GA4 (9.4) despite having the same conversion settings. This difference is substantial! Based on Google’s explanations, some differences are unavoidable because GA4 measures web data differently from UA. They may be right to a certain extent, but this account below has such unrealistic data discrepancies that Google is also unable to provide valid reasons and solutions.

Period: 1 July – 14 July

Not only that, many advertisers are also facing the same issue especially e-commerce advertisers. Various online forums and discussion boards have pointed out similar issues with many possible reasons and solutions, but there are still many unknown variables. Due to the limitation of resources by the GA support team, no further guidance or solid solutions were given to resolve this issue. In short, everyone is still in the stage of learning and adapting to this new analytics model and system.

There are also some cases where conversions can be quite close between UA and GA4 under the same conversion event setup. Even so, it is still very difficult to compare conversion counts.

GA4 vs UA

Firstly, it is important to understand how both GA4 and UA collect and report the data differently. UA operates on a session-based model, where it monitors user activity on your website until one of the following events occurs:

• After 30 minutes of inactivity.
• At midnight.
• When a user visits your website through one campaign, leaves and returns through a different campaign.

Based on an article from GA, there are 3 main sources of discrepancy:

1. Inherent distinctions between UA and GA4 properties

GA4 employs a distinct data model compared to UA. For instance, GA4 captures events while UA captures hits. Moreover, GA4 incorporates AI-powered solutions like behavioral and conversion modeling to support privacy-preserving technologies which are not present in UA.

2. Differences in setup 

The differences in the setup process can lead to variations in conversions between UA tags and GA4 tags. Factors such as site coverage, tag firing conditions and e-commerce schemas may differ.

3. Differences in settings

Conversion differences can arise due to various settings in UA, GA4 and Google Ads. These settings include elements like conversion count, filters, URL parameter exclusions and other configuration options that can impact how conversions are tracked and reported.

i. Conversion Counting

UA counts one goal conversion per session, while GA4 often counts one conversion per event. For example, when a user completes a goal 5 times in a single session, UA will show one conversion and GA4 will usually show 5. To align GA4 counting with UA goal counting, make sure the GA4 conversion counting method is set to ‘Once per session’.

ii. Attribution Modeling

GA4 introduces a more advanced attribution model compared to UA. It might attribute conversions differently than the traditional last-click attribution model used in UA. This can lead to variations in reported conversion numbers between the two platforms.

iii. Filters

UA filters work very differently from GA4 filters. It is common for UA filters to be in place and significantly alter the data inside a UA property (for example, “only show data from France”). GA4 has a very different set of possible filters. If UA filters reduce reported traffic, this can result in GA4 showing higher amounts of traffic. To minimize discrepancies, make sure both sites have included/excluded filters for internal and developer traffic as well as included only the referrals you want.

Google Ads & GA4 Discrepancies

We have also noticed a significant discrepancy between Google Ads and GA4, as shown in the account example above and here are some possible reasons:

1. Conversion window

This setting defines how long after a Google Ads touchpoint conversion credit can be attributed to that touchpoint. Often, this setting is set to a value of choice (for example, 90 days).

If you have set the click-through conversion window to 30 days, it means that after someone clicks the ad, Google Ads will be tracking if they convert within 30 days of that click. Hence, if the person revisits your site within 30 days via a different marketing channel and makes a purchase, Google Ads will count it as a conversion. 

2. Attribution model

This could also be the reason for the discrepancy where advertisers are able to assign which ad will be getting credit. Google Ads uses the last Google Ads click, but Analytics uses the last click across all channels. If let’s say, both Google Ads and GA4 are set to the commonly known “last-click” attribution, but the conversion numbers still do not line up, it means that the way both sites track the sale differently.

For example, a person clicks your ad about new sports shoes but did not make a purchase at that time. They then revisit your website later through an organic search result for the sports shoes and make a purchase. In this case, Google Ads would still report a conversion, but GA4 would give the credit to “organic” since it was the last touchpoint before the purchase and this would not be reflected in Google Ads.

3. Google signals and User ID

These settings help deduplicate users in GA4 properties. In UA, both settings only impact specific reports and a separate view. In GA4, they affect all information in the property.

Solutions:

A. Set the same Conversion Window

To minimize discrepancies, advertisers can ensure that both conversion window settings on Google Ads and GA4 are aligned.

B. Set the same Attribution Model

Advertisers can try to set the same Attribution model for both Google Ads and GA4. Although there may still be some minor differences in conversions, at least it can minimize the discrepancies between the two.

C. Adopting Google Ads conversion tag temporarily

The fastest way to counter the conversion discrepancies issue due to the instability of data in GA4. Advertisers may choose to set up the conversion tracking using the conversion tag in Google Ads to avoid discrepancies caused by the GA4 conversion events.

D. Enable Google signals and User ID in GA4 

This could help to reduce new/overall user counts by associating interactions that in UA would be considered from multiple users. Consequently, conversion credit can be attributed differently. These features are not expected to affect the total number of conversions in GA, but they can result in discrepancies when exporting data to Google Ads.

E. Reaching out to GA Support

A straightforward approach that Google would recommend advertisers to take. Since cases may vary based on different accounts, it is advisable to request further assistance from GA Support and address the issue directly.

F. UA remains a temporary solution

Since we have observed that UA is still receiving data in July, we may choose to continue referring to or using UA conversion tracking for our Google Ad account. This will ensure that the conversion data remains stable. However, it is important to remember that this is only a temporary solution.

G. Verify if the GA tags are consistently firing

This advice comes from Google specialists in Google Issue Tracker queries. They mentioned that there could be issues with the correct installation of Google tags (gtag.js) or Google Tag Manager (GTM) on your website. It is crucial to ensure that one or two snippets of code are added to each page of your website. The possible issues are:

Google tag (gtag.js)
i. The Google tag snippet is in the wrong place
ii. The Google tag ID is incorrect
iii. The Google tag contains extra whitespaces or characters

Google Tag Manager
i. The Tag Manager snippets are in the wrong places
ii. The Google tag ID is incorrect
iii. The GA4 Configuration tag has not been configured
iv. The GA4 Configuration tag does not have a trigger condition
v. The Tag Manager and Google tag snippets are both installed
vi. The Tag Manager changes have not been published

Additionally, advertisers who use GTM need to ensure that there is data when using dataLayer.push. It is worth knowing that GA4 is compatible with the UA ecommerce schema, but it does not work the other way round. If you have tagged your site for both GA4 properties and UA, avoid replacing your older schemas with GA4 ecommerce data types. Google recommends checking this guide to learn more about the setup.

In conclusion, there are still many unknowns and uncertainties in GA4 systems as this analytics model could still be in the early stage and not matured yet, causing significant conversion discrepancies between Analytics and Google Ads. However, there are still a lot of advantages to using GA4, such as the more accurate reporting view on unique users, advanced analysis reports, automated tracking for certain types of events and many more that could save a lot of time for advertisers in their digital advertising efforts. You may check this article for more details!