Question from Reddit user:
Hi just wondering what is more accurate when tracking Google Ads conversions? Google Analytics or Google Ads?
I was asked to set up both but the data from both isn’t matching. I know it is quite complicated with attribution etc. can some please explain how to use each one?
The conversions I’m tracking are form fills, phone calls and contact page visits.
Thank you in advance
Answer from Nabil:
The short answer is:
Neither Google Analytics (GA4) nor Google Ads conversion tracking is inherently “more accurate”; they are designed to answer different questions, which is why your numbers don’t match.
Google Ads tracking is optimized to report on ad performance using the specific “last click from a Google Ad” attribution model (or data-driven, etc., but focused on the ad touchpoint), whereas GA4 is optimized for full-journey user behavior using its own cross-channel attribution model.
The difference is due to distinct counting methodologies, attribution models, and lookback windows.
To achieve a single source of truth for your ad conversions and future-proof your tracking, you should implement a robust, server-side tracking solution using the Google Ads API and the Google Analytics Data API combined with GTM and a server environment like Stape or Google Cloud Platform.
The long answer is:
It’s completely normal for your conversion numbers to differ between Google Ads and Google Analytics, even when tracking the same user action like a form fill.
This isn’t a problem with accuracy but a difference in purpose and rules.
Google Ads tracking attributes a conversion based on its own set of rules, which are typically focused on the ad interaction.
It uses the Google Click ID (gclid) to link the conversion back to the specific ad, ad group, and campaign, and it often defaults to a “last Google Ads click” model in its raw reporting, giving 100% credit to the final ad interaction.
GA4, on the other hand, is designed for cross-channel analysis; it uses a default Data-Driven Attribution (DDA) model which assigns fractional credit across all touchpoints (Paid Search, Organic Search, Direct, Email, etc.) in a user’s journey.
Additionally, Google Ads can count conversions based on the date of the click, while GA4 counts the conversion based on the date of the conversion event, and they have different default lookback windows (e.g., 30 days in GA Ads vs. variable in GA4).
To solve this mismatch and gain ultimate control and data quality for events like form_fill and phone_call_event, the definitive solution is to use a server-side tracking architecture leveraging the Google Ads API and the Google Analytics Data API.
You would use Google Tag Manager to capture a reliable, first-party cookie ID and the Google Click ID (gclid) when a user lands on your site from an ad.
When the user completes the conversion (form fill, contact page visit), you send the conversion event server-side via an environment like Stape or Google Cloud Platform.
From this server, you can then do two things: first, you can use the Google Ads API to send the conversion data directly back to Google Ads, effectively utilizing Enhanced Conversions.
This ensures Google Ads receives highly accurate, first-party data and uses the gclid to correctly attribute it within its platform.
Second, you can use the Google Analytics Data API to ensure your server-side conversion event is sent to GA4 with all the rich session parameters, guaranteeing your GA4 reporting has the highest quality first-party data.
By centralizing the data collection and distribution through your own server, you bypass client-side issues like ad blockers and browser restrictions, and you can use the APIs to validate and send consistent data to both platforms, effectively creating a single, reliable source of truth for analysis and bidding optimization.
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