Top Reasons for Discrepancies Between Google Ads and Google Analytics 4 Conversion Data You Need to Know

Before launching a Google Ads campaign, it’s essential to predefine the conversion events you want to track. This allows you to directly measure the effectiveness of your ads using conversion data.

Both Google Ads and Google Analytics 4 (GA4) offer their own conversion tracking tools. However, why is there often a difference in the conversion data between the two platforms? In this article, we’ll explore the key reasons behind these discrepancies.

Conversion Tracking in Google Ads and Google Analytics 4

Conversion tracking involves monitoring the key actions you want users to take on your website or app. These actions vary across different businesses and industries.

For e-commerce, it’s crucial to track events such as “Add to Cart,” “Checkout,” and “Purchase Success.” Sometimes, tracking repeat purchases is also important. For SaaS businesses, tracking events like “Subscription,” “Demo Request,” and “Online Payment” is essential.

Without tracking these actions, you won’t be able to measure the effectiveness of your advertising campaigns.

There are two ways to track conversions in Google Ads:

  1. Install and Use Google Ads Conversion Tracking Code:
    This involves placing a piece of code on your website that tracks specific user actions.
  2. Import Conversion Events from Google Analytics 4:
    This method allows you to import predefined conversion events from GA4 into Google Ads for more integrated tracking.

For the first method, you must either directly add the code snippet to your website or use Google Tag Manager to insert the code:

If you choose the second method of importing conversion events from GA4, you must first link GA4 with your Google Ads account. The process is straightforward and can be easily found through a quick search.

Both of these conversion tracking setups can track the same events (such as purchase events), which might lead to confusion for advertisers: Should I use one method, or both?

First, it’s important to understand that both types of conversion tracking use the same gtag code (previously, Google Ads used the Conversion code, and GA used the Analytics code, but Google has now unified them into the gtag code). However, the conversion data you’ll see in Google Ads and Google Analytics 4 reports will still show discrepancies. These differences are inevitable, and I’ll explain why in detail.

Differences Between Google Ads and Google Analytics 4 Conversion Tracking

There are numerous reasons why conversion data might differ between Google Ads and Google Analytics 4 (GA4). Below are the main factors that contribute to these discrepancies:

  1. Attribution Models:
    Currently, both GA4 and Google Ads offer only Last Click and Data-Driven Attribution (DDA) models. If different models are used for conversion tracking on each platform, the final conversion data will inevitably differ.For example, if a user sees your ad, visits your website, leaves, and then returns via organic search to complete a purchase, the Last Click attribution would credit the conversion to organic search. However, under the DDA model, both the ad and the organic search would share the credit for the conversion.
  2. Attribution Window (Lookback Window):
    By default, Google Ads has a 30-day lookback window, while GA4 has a 90-day lookback window for key events. Different lookback windows can result in conversions being recorded in GA4 but not in Google Ads.Note: In GA4, conversions are referred to as key events, but they are still labeled as conversions when shared or imported into Google Ads.
  3. Conversion Attribution Date:
    Google Ads attributes conversions based on the date of the ad click, while GA4 attributes them based on the date the conversion occurred. For instance, if a user clicks an ad on March 21 and makes a purchase on March 25, Google Ads will record the conversion on the 21st, whereas GA4 will record it on the 25th.
  4. Conversion Data Delay:
    Conversion data in Google Ads is reported faster than in GA4, where it can take 24-48 hours (and sometimes up to 72 hours) for the data to appear in reports.
  5. Counting Methods:
    Depending on your chosen counting method—whether to count each conversion during the same session or only once—this can affect the data seen on both platforms. For example, if you use “count every conversion” in GA4 but “count once” in Google Ads, the conversion data will differ.
  6. Refunds:
    If you’ve set up refund tracking on one platform but not the other, the numbers will vary due to refund transactions.
  7. Cross-Device Tracking:
    Google Ads’ tracking mechanism allows for cross-device tracking, but GA4 can only achieve this if Google Signals is enabled.
  8. Conversions Not Tracked in GA4:
    Google Ads can track conversions from phone calls and store visits, while GA4 can only track conversions that happen on your website or app. Therefore, these types of conversions won’t be tracked in GA4.
  9. Impact of Consent Mode and Ad Blockers:
    If users do not consent to being tracked by cookies on your site or are using ad-blocking extensions, GA4 may not be able to record user interactions, let alone conversions. Google Ads can bypass this issue as its tracking code triggers only when a conversion occurs.
  10. Conversion Exclusions:
    Google Ads can exclude conversion data if it detects fraudulent clicks, but these conversions might still appear in GA4. Additionally, if marketers conduct any conversion tests on their website, this test data will show up in GA4 but not in Google Ads reports.

There are, of course, many other factors that could cause discrepancies. Due to time constraints, I’ve only listed the most significant ones. I’ll provide a comprehensive list, including technical factors, when I have more time.

Additional Advantages of Google Ads Conversion Tracking

In addition to the above-mentioned differences, Google Ads conversion tracking offers several advantages:

  • If you use automated or smart bidding strategies, Google Ads provides better modeling and prediction capabilities.

Advantages of Google Analytics 4 Conversion Tracking

Importing conversion data into a Google Ads account also has its benefits:

  • Using GA4 conversions can be quick and easy, with no need for additional conversion tracking setup in Google Ads, making it ideal for advertisers who are not familiar with code installation.
  • Google Ads can use all the traffic data provided by GA4 to optimize smart bidding. If your traffic structure is very complex, importing GA4 events might be more suitable, whereas if your traffic structure is relatively simple, using Google Ads conversion events may be more appropriate.

When you import GA4 conversions into Google Ads, they are marked as “secondary conversions” and are not used for bid optimization. Therefore, you should mark important events as “primary conversions.”

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