Server-Side Tagging with Google Tag Manager

Foreword

In August 2020, Google introduced GTM Server-side with the promise of improving performance, security, and reliability of web marketing setups. This is a new Tag Management tool that modifies the collection mechanism to offer unprecedented control over data that is collected and then sent to various partner services (Google, Meta, etc.). Since September 2021, GTM Server-side is no longer in beta and is globally available for Tag Manager and Tag Manager 360.

In a context where data control is essential for managing marketing actions but increasingly complex due to browser restrictions, the development of adblockers, and GDPR regulations, GTM Server-side promises to be a major and soon indispensable tool to help players gain an edge over their competitors and improve their marketing performance.

What is GTM Server-side? How can server-side tagging integrate into your data collection setup? What are the concrete advantages and current limitations?

Understanding GTM Web and GTM Server-side Architecture

Classic GTM Web Architecture

For the same action (e.g., page view, add to cart, or purchase), multiple browser-side tags send the same type of data to different services.

GTM Server-side Architecture

A Server-side implementation is not a complete system overhaul: it should be seen more as an evolution that complements and improves your current setup.

The Importance of Google Analytics 4 Protocol for GTM Server-side

GTM Server-side reveals the importance of the Google Analytics 4 (GA4) measurement protocol in Google's data marketing roadmap.

Indeed, GA4 is designed to be a gateway between Web and Server containers and to trigger other services (such as Google or Meta, for example).

👉 GA4 is "the backbone" of GTM Server-side collection.

Advantages of GTM Server-side

1 - Web Performance and Data Control

With GTM Web, you end up using dozens of browser-side tags that make dozens of requests for the same action (e.g., page view, add to cart, or purchase):

• This weighs down your site with JavaScript resources: UX and web performance issues.
• This complicates tag governance and control of your 1st-party data: some tags call other external services ("trackers") that collect data (sometimes critical) about your users. This creates security vulnerabilities and exposes you to GDPR issues.

With GTM Server-side, a single tag (Google Analytics 4) on the browser side can carry the necessary information for all other eligible services (Meta, Google, etc.). The Server container sends data to different services, server-side, without being dependent on the browser context.

👍 Improved data governance and control

👍 Drastic reduction of browser-side resources needed

2 - Adblockers and Browser Policy Changes

Web container tags call external resources (e.g., google-tag-manager.com, facebook.com, etc.) that are easily identifiable by adblockers and browsers: this makes your data collection setup more fragile and you lose more and more important data.

GTM Server-side allows calling all resources and libraries in a 1st-party context, i.e., without calling google.com, facebook.com, etc. This makes the tagging setup more robust against browser policies and other adblockers!

👍 Improved data collection reliability (between 15% and 30%)**based on an analysis of EdgeAngel clients conducted in July 2021 with the Capture solution

3 - Cookies: Marketing Campaign Attribution and Contribution Analysis

GTM Web tags create cookies with a JavaScript method and are thus exposed to new policies from certain browsers: the 1st-party cookie lifespan is limited to 7 days or even 24h in some cases for Safari (ITP) and Firefox (ETP).

This completely limits campaign performance analysis in terms of attribution and contribution.

With GTM Server-side, vendor cookies are created with the HTTP server response and not with a JavaScript method, making them more robust. They are less limited by browser policies (e.g., ITP on Safari) while respecting the GDPR framework you have defined in your organization.

👍 Improved ability to analyze user journeys and attribute conversions to the right marketing sources

sGTM Collection Architecture on GCP or AWS

GTM Server-side uses Google Cloud Platform (GCP) services by default but can also be implemented with any other cloud provider, such as Amazon Web Services (AWS).

The sGTM collection infrastructure is completely independent of the existing IT infrastructure or Ecommerce solution, ensuring no impact on existing services (no SPOF).

GTM Server-side Implementation Costs and Billing Considerations

GTM Server-side requires deploying machines on Google Cloud Platform (GCP) and involves billing considerations:

• This amounts to between €70 and €150/month for example on GCP with 3 App Engine instances (Google recommendation) or with our partner Addingwell
• It is possible to limit billing issues by limiting GCP services (minimizing logs) and rationalizing server hits as much as possible.

The project itself is clearly not as heavy as it seems and requires little or no technical team involvement. Configuring the GTM Server-side container with GA4 and Meta Conversions API can be done in a few days 😃

Current Limitations of GTM Server-side

• The GTM Server-side solution opens up many possibilities for data control. But it is important to move forward on this subject with a good knowledge of GDPR issues and a well-defined framework at the risk of misusing user data.

Case Study: Improving Data Collection

Analysis aimed at determining the potential gain of an analytics and media tracking implementation with server-side GTM (sGTM) compared to a traditional implementation with GTM Web only.

Configuration Detail

• sGTM implementation with domain delegation to be in a 1st-party context
• sGTM configured on a GCP infrastructure with 3 App Engine instances by default, with auto-scale up to 6 instances
• 3 third-party services set up on sGTM: GTM Web (library loading), Google Analytics 4, and Meta Conversions API

Test Detail and Analysis Approach

• Double Google Analytics implementation: one via sGTM and the other via GTM Web
• Configuration of the Meta Pixel and Conversions API in parallel with event deduplication
• Nature of the analysis: main client conversion event, namely the transaction or lead (unique identifier per event)
• Identical rules and conditions for triggering browser-side tags and server-side tags (especially regarding consent status)

Analysis carried out on a panel of 5 web setups, with a mathematically significant volume of data (more than 400 conversion events per setup).

Results

Google Analytics

Method: we compared the data feedback from the sGTM protocol vs GTM Web compared to the back-office data (100% base).

👍 sGTM allows reducing the gap with the back office by 15% to 30%

Ex: if you have a gap with your BO of 20%, sGTM will allow you to bring it down to between 14% and 17%.

Meta (Pixel and Conversions API)

Method: analysis of server-side events that were not deduplicated by Meta because they were sent via the browser

👍 sGTM allows recovering between 10% and 20% more data with Meta CAPI and the Pixel than via the Pixel alone

Ex: if you send 1000 conversions to Meta via the Pixel, activating the Conversions API will allow sending between 100 and 200 more conversions.

EdgeAngel Insights and Recommendations

At a time when advertisers are finding it increasingly difficult to collect data (ITP, Meta, iOS, etc.), implementing this project provides a definite advantage in steering your marketing campaigns (e.g., targeting and bidding strategies).

We recommend activating GTM Server-side for any digital player, and even more so for those for whom data governance is essential within the company. And especially if the subject of attribution data analysis plays an important role in their marketing strategy.

At EdgeAngel, we accompany dozens of advertisers on this issue. Do not hesitate to contact our team of experts to discuss this subject >