Server-Side Tracking Explained: Why You're Missing Up to 30% of Your Data

Imagine: you invest hundreds or even thousands of euros monthly in Google Ads, but your analytics data only tells you 70% of the story. Sounds frustrating? That's the reality for most businesses that still rely entirely on traditional client-side tracking.

In this article, we explain what server-side tracking is, why you're probably missing data, and how you can fix it.

The Problem: Why Are You Missing Data?

Before we discuss the solution, it's important to understand where the problem comes from. There are four major causes for incomplete tracking data.

1. Ad Blockers

An estimated 25-40% of internet users have an ad blocker installed. Most ad blockers don't just block advertisements but also tracking scripts like Google Analytics and the Facebook Pixel.

This means a significant portion of your visitors is completely invisible in your analytics. You don't see them arrive, you don't see their behavior, and you don't see their conversions.

2. Intelligent Tracking Prevention (ITP)

Apple's Safari browser (used by approximately 20-25% of Belgian internet users) has Intelligent Tracking Prevention built in. ITP limits cookie lifespans:

• First-party cookies via JavaScript last a maximum of 7 days
• Third-party cookies are completely blocked
• Link decoration means query parameters are removed after 24 hours

This means that if a visitor visits your website via Safari, leaves, and returns 8 days later to make a purchase, you can no longer attribute that conversion to the original source.

3. Firefox Enhanced Tracking Protection

Firefox blocks third-party tracking cookies by default and has increasingly strict privacy measures. With a market share of approximately 5-8% in Belgium, this contributes to data loss.

4. Cookie Consent and GDPR

In Belgium and the rest of Europe, you're required to ask for consent before placing tracking cookies. On average, only 50-70% of visitors give consent. The rest are not tracked.

The Total Loss

When you combine all these factors, it's realistic that you're missing 20-30% of your website data. For a business spending €5,000 monthly on Google Ads, this means you're potentially not seeing hundreds of conversions, and therefore can't optimize for them.

What is Client-Side Tracking?

To understand server-side tracking, we first need to look at how traditional tracking works.

With client-side tracking, everything runs in the visitor's browser:

1. A visitor opens your website
2. The browser loads your tracking scripts (Google Analytics, Facebook Pixel, etc.)
3. These scripts collect data about the visitor's behavior
4. The data is sent directly from the browser to Google/Facebook/etc.

The problem: everything happens in the browser. And the browser is precisely where ad blockers, ITP, and cookie consent intervene.

Visual Representation

Visitor → Browser → [Ad Blocker / ITP / Consent] → Google Analytics
                            ↑
                    Data is lost here

What is Server-Side Tracking?

With server-side tracking, data doesn't flow directly from the browser to Google or Facebook. Instead, the browser sends data to your own server, which then forwards it to the analytics platforms.

How Does It Work in Practice?

1. A visitor opens your website
2. The browser sends data to your own (first-party) server endpoint
3. Your server processes the data
4. The server forwards the data to Google Analytics, Google Ads, Facebook, etc.

Visual Representation

Visitor → Browser → Your Server → Google Analytics
                                 → Google Ads
                                 → Facebook

Why Does This Solve the Problem?

• Most ad blockers recognize calls to third-party domains (google-analytics.com). But when data goes to your own domain (for example tracking.yourbusiness.be), it won't be blocked.
• Cookies set by a server (HTTP cookies) have a longer lifespan than JavaScript cookies. Server-set first-party cookies are not limited to 7 days by ITP.
• You get more control: you decide which data you forward and can filter sensitive information before it reaches third parties.

Server-Side Google Tag Manager

The most commonly used implementation of server-side tracking is via Server-Side Google Tag Manager (sGTM).

How Does sGTM Work?

Google Tag Manager has a server container in addition to the traditional web container. This runs on a cloud server (usually Google Cloud Platform) and acts as an intermediary between the browser and the analytics platforms.

The Architecture

1. The web container (client-side) sends data to your server container via a first-party endpoint
2. The server container receives the data, processes it, and forwards it to the right destinations
3. Tags in the server container handle GA4, Google Ads conversions, Facebook CAPI, etc.

Advantages of sGTM

• All data flows through your domain, giving you a first-party context
• Server-set cookies bypass ITP restrictions, providing a longer cookie lifespan
• Fewer scripts load in the browser, resulting in a faster website
• You can add server-side data like CRM data and customer value through data enrichment
• You can filter PII (personally identifiable information) before it reaches third parties for better privacy control

Enhanced Conversions: The Perfect Complement

Enhanced Conversions is a Google feature that works perfectly with server-side tracking. It allows you to send hashed customer data (email, phone, name, address) along with your conversions.

Why Is This Important?

Google uses this hashed data to match conversions with users, even when cookies aren't available. This increases your conversion attribution by 10-15%.

How Does It Work?

1. A customer fills in a form or makes a purchase
2. The customer data is hashed (encrypted) with SHA-256
3. The hashed data is sent along with the conversion tag
4. Google matches the hashed data with logged-in Google users
5. The conversion is correctly attributed, even without cookies

Enhanced Conversions via sGTM

The ideal setup combines enhanced conversions with server-side tracking:

• Server-side tags can enrich data with backend information, giving you more data
• More data points lead to higher match rates and better matching
• Data is hashed before it leaves your server, keeping everything privacy-compliant

What Are the Costs and Considerations?

Server-side tracking isn't a free lunch. There are a few things to consider.

Hosting Costs

Your server container runs on a cloud platform, usually Google Cloud Platform (GCP). Costs depend on your traffic:

• Low traffic (up to ~100,000 hits/month) starts from a few euros per month
• Medium traffic (100,000 - 1,000,000 hits/month) runs at tens of euros per month
• High traffic (1,000,000+ hits/month) scales up, but costs remain relatively low compared to your advertising budget

Technical Complexity

The setup is more complex than standard client-side tracking:

• You need knowledge of cloud platforms
• DNS configuration for your custom domain
• Configuration of the server container
• Testing and validation of the data flow

Maintenance

Just like your web container, your server container needs to be maintained:

• Updating tags
• Adding new integrations
• Monitoring server health
• Keeping an eye on costs

Is Server-Side Tracking Worth It?

The short answer: yes, for most businesses that advertise seriously.

Server-side tracking is essential if:

• You spend more than €1,000 monthly on online advertising
• You notice that your conversion numbers in Google Ads don't match your actual sales
• You have a large share of Safari users
• You want to comply with GDPR without losing all your data
• You want to improve your ROAS through better data

Server-side tracking is less urgent if:

• You have a very small website with little traffic
• You don't advertise and use analytics purely for informational purposes
• Your budget for setup and maintenance is very limited

The Impact on Your Google Ads Performance

Better data leads directly to better campaign results:

• Google's Smart Bidding works better because it has more conversion data to optimize with
• Remarketing lists are more complete, giving you better audiences
• You know which campaigns and keywords truly convert, ensuring correct attribution
• Through better optimization, you get more results from the same budget, leading to higher ROAS

Businesses that switch to server-side tracking see on average a 15-25% increase in reported conversions and a noticeable improvement in their campaign performance.

Getting Started

Implementing server-side tracking is a technical project, but the return is more than worth it. The steps in brief:

1. Audit your current tracking to find out how much data you're currently missing
2. Plan your architecture: custom domain, cloud platform, data flow
3. Implement sGTM by setting up and configuring the server container
4. Migrate your tags for GA4, Google Ads, and Facebook CAPI
5. Activate Enhanced Conversions for maximum conversion attribution
6. Monitor and optimize by comparing data before and after the migration

Want to know how much data your business is missing? At Saerens Advertising, we perform a free tracking audit where we map out exactly how many conversions you're not seeing. We then help you with a professional server-side tracking implementation so you have the complete picture again. Get in touch for a no-obligation conversation.