GA4 has been undercounting conversions
We compared GA4’s event conversion tracking with the previous Universal Analytics session tracking. We found that GA4 was capturing around 15% fewer conversions compared to UA when Google Analytics is used as a conversion tracking method within Google Ads. When compared to Google Ads tracking, GA4 was tracking around 40% fewer conversions within Google Ads.
After doing this, we used an advanced Google Ads tracking method with server-side tracking. This attributed 15% more conversions relative to the standard Google Ads tracking pixel, highlighting the undercounting of conversions by GA4, UA, and the standard Google Ads tracking pixel.
In summary, GA4 records fewer conversions than its predecessor, UA. GA4’s undercounting of conversion could come down to browser-based issues:
The blocking of client-side tracking pixels
GA4’s tracking relies on client-side browser tracking. Many browsers now use privacy tools, ad blockers, and other mechanisms that prevent tracking pixels from firing. When these pixels are blocked, GA4 has no way of recording the conversions.
What this means for your campaigns
Not being able to capture a large portion of conversions has major implications for truly understanding your campaign performance. When conversions are undercounted, other key metrics like cost per conversion or return on ad spend are skewed, leading to poor optimization, budgeting, and targeting decisions.
Going forward, it’s crucial for businesses to recognize the limitations of GA4 tracking - relying solely on GA4 tracking doesn’t give you the full picture of your data.
Using Google Ads tracking pixels to provide you with more data
To remedy the undercounting issues, advertisers should explore using Google Ads tracking pixels to get a better understanding of campaign performance. This method tracks conversions from Google Ads campaigns only.
Google Ads tracking provides you with a large amount of data that can then be used to optimize your Google Ads channel, as well as give you an accurate figure when it comes to conversions. GA4 uses a different attribution model than both the old UA tracking and Google Ads tracking. Overall we saw a significant reduction in conversions and revenue attributed towards Google Ads traffic on GA4.
Combining Google Ads tracking with GA4 can help you get a better understanding of your campaigns, giving you more data to inform your strategy.
If you see a drop in conversion rates or campaign performance through GA4, your issue could be undercounting. Using GA4 alongside other tracking methods can provide you with the information you need to optimize successfully.
