Bigcommerce Conversions vs Google Ads Conversions
We are running Google Shopping ads for our Bigcommerce store and have become super confused by the discrepancy between the recorded conversions. For the period between August 1 ~ Sept 19 Bigcommerce records 48 orders as referred from adwords (Campaign UTM) while Google Ads is only showing 12 conversions in the same period. Our avg days to conversion is 0.3 so why is Google Ads missing so many? We use an enhanced tracking conversion tag on our confirmation page as primary conversion goal. We also have Analytics linked as secondary but that shows even fewer conversions.
Can anyone explain what we might be missing or not understanding here? Is Bigcommerce overestimating the conversions or is Ads underestimating? Which data should we rely on and how can we improve this?
The short answer is:
The discrepancy is highly likely due to limitations of client-side tracking, such as ad blockers, browser restrictions like Intelligent Tracking Prevention (ITP), and network latency, causing the Google Ads conversion tag to fire inconsistently or fail.
BigCommerce’s UTM-based referral tracking is less susceptible to these issues as it records the source at the time of order, leading to the higher count.
To reliably match your BigCommerce order data with Google Ads, you must implement server-side tracking using the Google Ads API or the Google Analytics Measurement Protocol combined with a robust system like Google Tag Manager (GTM) Server Container and Stape.
This approach captures the conversion event directly from your server, bypassing client-side blockers and ensuring maximum data accuracy for optimization.
You should rely on the server-side implemented data as the most accurate reflection of revenue attributable to Google Ads.
The long answer is:
The core issue lies in the fundamental difference between how your BigCommerce platform and your existing client-side Google Ads conversion tag record data.
BigCommerce’s internal UTM tracking is recorded server-side when an order is finalized, making it a reliable, high-fidelity source of order count, albeit potentially over-attributing to the last-click source if the UTM parameter persists.
Conversely, your client-side Google Ads Enhanced Conversion tag relies on the user’s browser to execute JavaScript, which is precisely where ad blockers, network errors, and privacy-focused browser features like ITP intercept and prevent the tag from firing, resulting in the significantly lower count of 12 conversions.
Neither figure is perfectly correct under your current setup, but the BigCommerce number is closer to your actual order volume.
To solve this, you need to transition to a server-side tracking model, which will unify the data closer to the BigCommerce figure and provide the accurate reporting needed for bid optimization.
The most technical and effective solution involves using the BigCommerce API with GTM Server Container and Stape.
You would configure a webhook or polling mechanism via the BigCommerce API to retrieve new order data the moment it occurs on the server, which is then sent to your GTM Server Container.
From the Server Container, you use the Google Ads API (specifically, the Conversion Upload Service) or the Google Analytics Measurement Protocol to directly transmit the conversion event and its unique Google Click ID (gclid) to Google’s servers.
This server-to-server connection is immune to client-side blockages, ensuring near-perfect transmission of conversion data.
The cost-effectiveness comes from maximizing the performance of your Google Shopping campaigns, as they will now optimize against accurate, high-volume conversion data, preventing misallocation of budget that occurs when relying on the currently underreporting client-side tag.
Furthermore, this method also sets the stage for future integration with the Merchant API to automate product feed updates, further streamlining your marketing technology stack.
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