Track 100% of conversions with server-to-server tracking
Classic approach to conversion tracking is to place tags on the order confirmation page (called Thank you page too). This is technically easy as all cookies and attribution data should be available, the problem is that sometimes users don't end up on that page at all.
Either they just drop off by closing their browser tab too early or the specific payment method has complex flow (think about Buy Now Pay Later providers that need to perform online credit assessment).
Luckily server-side GTM allows to avoid any of those problems by enabling server-to-server tracking, where things happen behind the scenes so no user action that interrupt that.
Why traditional client-side tracking fails
Client-side tracking relies heavily on user behavior patterns that marketers can't control. When customers complete purchases through third-party payment processors like Klarna, Afterpay, or PayPal, they often get redirected multiple times before potentially returning to your thank you page. Each redirect introduces another opportunity for data loss.
Ad blockers present another significant challenge. With roughly 25-30% of users running some form of ad blocking software, a substantial portion of your conversions simply vanish from your analytics. This creates blind spots in your marketing attribution and makes budget optimization nearly impossible.
Browser crashes, network timeouts, and users simply closing tabs after payment confirmation further compound the problem. You end up with incomplete data that undermines confidence in your marketing performance metrics.
How server-to-server tracking works
Server-to-server tracking moves the conversion recording process away from the user's browser to your backend systems. Instead of relying on JavaScript tags that fire when users land on specific pages, your server communicates directly with advertising platforms and analytics tools.
The process typically works like this: when a payment is successfully processed in your system, your server immediately sends conversion data to Google Ads, Facebook, GA4, and other platforms. This happens regardless of what the user does after completing their purchase.
Your payment processor (Stripe, PayPal, etc.) can trigger webhooks that notify your server about successful transactions. These webhooks carry all the necessary information to attribute the conversion back to the original marketing touchpoint, including customer IDs, transaction values, and timestamps.
Setting up server-side GTM for conversions
Server-side Google Tag Manager acts as the bridge between your backend systems and marketing platforms. Unlike client-side GTM that runs in users' browsers, server-side GTM operates on a dedicated hosting server, ensuring reliable data transmission.
First, you'll need to configure your server container to receive conversion events from your backend. This involves setting up custom GTM clients that accept POST requests containing conversion data. Your e-commerce platform or custom checkout system sends transaction details to these endpoints immediately after payment confirmation.
The server container then processes this data and forwards it to various advertising platforms using their respective APIs. For Google Ads, this means utilizing the Google Ads Conversions API. Facebook uses the Conversions API, while other platforms have similar server-side endpoints.
Benefits beyond tracking reliability
Server-to-server tracking offers advantages that extend beyond simply capturing more conversions. Data quality improves significantly because you're working with clean, structured information from your backend rather than potentially corrupted browser data.
Privacy compliance becomes easier to manage since you control exactly what data gets shared with advertising platforms. You can implement sophisticated consent management and data filtering at the server level, ensuring compliance with GDPR, CCPA, and other privacy regulations.
Performance optimization opportunities emerge when you have complete conversion visibility. You can confidently increase budgets on campaigns that previously appeared to have poor performance due to tracking gaps. This often reveals that certain traffic sources or campaign types were actually profitable all along.
Attribution modeling becomes more accurate when you capture all conversions consistently. You can implement custom attribution logic on your server, taking into account factors like customer lifetime value, repeat purchases, and cross-device behavior patterns.
Implementation considerations
Technical complexity increases with server-side implementation compared to simple pixel-based tracking. You'll need developers familiar with APIs, webhook processing, and potentially server infrastructure management if you're not using dedicated managed sGTM hosting.
Testing and validation require more sophisticated approaches than client-side tracking. You'll need to verify that conversion data flows correctly through your entire system, from payment confirmation through to advertising platform reporting.
The biggest challenge is how to connect server-side tracking with browser-side information. The user browser even without 3rd party cookies is still the key source of attribution data, such as page referrers, query parameters and first party cookies. In order to get correct attribution in reporting and advertising tools additional storage of that data is required. First it will be populated when user initiates the checkout and then it needs to be referenced at the time of server webhooks.
Our solution
Server-side tracking (do not confuse with serve-side tagging, check our mini-class) is the most reliable way of ensuring all conversions are covered by analytics and advertising tools. For some payment methods such as Stripe Payment Links it is the only way to really track transactions across multiple channels.
On the other hand, it goes far beyond class, browser-side pixels and tagging and require more advanced tools such as storing and processing cookies and other attribution data on the backend.
We implemented that sucesfully multiple times. Consider our services or Care plan to get it done.