A Guide to Integrating GTM Server-Side & Conversions API

Raisul Islam
First published July 10th, 2024
Last updated July 15th, 2024
Prepare for the end of third-party cookies with GTM Server-Side & Conversions API integration for improved data strategy and performance.
A Guide to Integrating GTM Server-Side & Conversions API

For the third time, Google has extended the end date for third-party cookies, this time until 2025. Let’s explore how you can prepare for this change by integrating GTM Server-Side & Conversions API.

This is a webinar write-up of Barbara Kalicki’s talk at GA4ward V5. Find her slides here and a YouTube recording of her session below:

The cookie is down to its last crumbs

Since 2016, ad blockers have been blocking cookies. In the image below, we can see how the usage of cookies has decreased across different browsers.

how the usage of cookies has decreased across different browsers

As major browsers deprecate cookies, pixels will no longer be a reliable source for off-site targeting, measurement, and optimisation. To put this into perspective, let’s look at a typical user journey.

A consumer comes to your website and a third-party pixel is placed on their browser. This follows them and sends data back to ad platforms. This can be used for various purposes, such as to optimise user journeys.

A typical demonstration of consumer journey

Unfortunately, when browsers start blocking these cookies, there will be no data going to ad platforms. This means all your marketing and even some website analytics data will be lost. This is why people should start thinking about a first-party data strategy now.

Digital performance is dictated by the decision-making algorithms of ad platforms. This is influenced by users who see and interact with your advert. To retain critical conversion signals in-platform, it’s important to supply the algorithm with 1st party data.

By doing so, you can see a performance lift of up to 38%. Currently, because of ad blockers, we’re seeing a 75% signal loss. Many of the interactions you have with website users on your site are no longer captured by conversion signals.

What is CAPI?

Similar to platform pixels, Conversions API (CAPI) is a durable solution that creates the pipes to enable businesses to collect and share their customer data. It draws information from a variety of sources including web, app, and offline events.

CAPI is a direct connection between the client and platform servers (the pipes). Conversion
events and other relevant online and offline data can be shared with the platform via the CAPI

The solution enables a range of platform use cases. This includes building custom audiences, delivering personalised advertising and brand experiences, and optimising and measuring campaigns. CAPI is a privacy-safe, advertiser-controlled solution that will replace platform pixels.

Almost all advertising solutions offer CAPI, although they’re sometimes referred to by a different name. For example, Pinterest has an ‘API for conversions’.

What really changes with CAPI?

Unlike a third-party cookie, a user has complete control over their first-party data with CAPI. The tool will help you increase your match rates and improve the decision-making algorithm. This means you improve the marketing of your brand to your customers.

All data sent through CAPI is sent in hashed PII, meaning it is already privacy-safe. There’s no need to worry about regulations, as all data is collected and sent with user consent.

Some other highlights of CAPI include:

  • Browser settings do not impact data sharing.
  • Browser performance does not impact data sharing.
  • Consent is still collected, and privacy controls are maintained.

What is match rate?

Match rate helps to display your ad as well as improve your CPC and ROAS. The image below shows how the match rate works using CAPI.

Firstly, data is collected and hashed on our site through first-party cookies. The ad platform then identifies whether they have served a user with an ad before. If so, they will be matched with the ad that had previously caused them to convert.

This information strengthens your first-party data strategy. You’re no longer reliant on a third-party platform and are collecting and sending information yourself. This data can help enhance your CDPs, and other martech tools, and improve identity resolution.

How the match rate works using CAPI

CAPI integrations

Advertisers have three different options when it comes to standing up CAPI.

Individual media platforms

Individual media sets API connections to each ad platform that you advertise on. They provide individualised control across each media platform and within each business manager.

Be mindful, however, that this solution requires developer resources for the integration and maintenance of multiple APIs.

Independent providers

Independent providers offer unified API platforms that enable data sharing to multiple CAPI endpoints through a single configuration. They drive governance and control across all
media platforms through a single command centre.

These providers Typically require a new platform to be added to your existing tech stack.
There are also varying levels of resources needed.

Existing tech stack

Leveraging your existing CDP or tag management relationships, you can share conversion signals with media platforms. There are some downsides to this approach. You’ll be tied to platform restrictions for supported media endpoints. Some platforms, like ssGTM, require heavy developer investment.

Questions to determine the right option for you

To identify the best solution, ask the following questions when standing up CAPI.

  1. How many platforms do you run media campaigns on?
  2. How important is it to have direct control and ownership of all APIs?
  3. What level of technical expertise and resources do you have internally to set up and maintain one or more conversion API connections?
  4. Do you have a cloud server capable of handling the necessary volume and frequency of conversion data?
  5. What data security measures are in place to protect against data breaches or unauthorised access?
  6. How much flexibility do you anticipate needing for future integrations? To help you answer this, consider the number of brands, markets, and new events you may be tracking.
  7. Do you work with any existing tech partners that offer CAPI services?
  8. What level of support and service is needed by your team?

Server-side GTM vs CAPI

You wouldn’t set up both GTM Server-Side & Conversions API. Both solutions collect first-party data and send it to ad servers.
The two approaches are compared below:

Setup typeOne-time custom setupCAPI SaaS with support
Cloud server ownershipClient – Google CloudClient or independent provider
API updates & maintenanceManaged by ClientClient or independent provider
IT dependenceRequire custom developmentNo-code & negligible
Setup time1 Week (only Meta web CAPI)Self-serve setup in 15 min
Cost of implementationOne-time cost per channel and use-caseSingle cost based on the number of integrations and volume
Cost of infrastructureClient-owned Google Cloud billingNone
Available channelsSeparate implementations per channelAmazon, Meta, TikTok, Google Ads
Notes• Web CAPI for only 1 Ad-platform
• Experience with Google Cloud & owning ssGTM
• Moderate IT bandwidth to manage and scale
• CAPI on multiple channels and use
cases (Web, Offline, Lead Forms)
• Low IT bandwidth

The GTM Server-side approach

Server-side tagging brings the concepts of Google Tag Manager to the server. It allows you to run a Tag Manager container in the cloud. As with CAPI, with Server-side, you have complete control over your data. You are free to send data from any of your sources (websites, apps, devices, etc). The server container will shape and route the data to the appropriate destinations.

The process of setting up a server is easy. You’ll need developer help, however, to insert API code into tags.

To set up GTM server-side, click on ‘Create account’ or ‘Create container’ > ‘Select server
under target platform’. This will create another instance of your GTM, enabling GTM server-side to run.

'Server' target platform is highlighten in the creating container page of GTM

The image below displays the individual steps for configuring a new tagging server.

Individual steps for configuring a new tagging server

Benefits of GTM Server-Side Tagging and Conversions API Integration

Every company now needs first-party or zero-party data. This is because this form of data has received consent from the user before being collected. With both GTM Server-side and CAPI, we take control of this first-party data. We can decide what to send and when to send it.

Benefits of GTM Server-Side Tagging and Conversions API Integration

With GTM Server-Side & Conversions API we can connect offline and online data, app data, and many other sources. This increases the signals that are being sent to ad platforms and data sent to analytics tools.

There are several other broader benefits beyond this. These include:

  • Privacy-centric – Conversions API was designed and built with marketing data privacy in mind. Conversions API gives advertisers control over what data to share and when.
  • Stronger signals and better performance – As browser-related issues do not impact CAPI, we can expect increased conversion visibility and quality. This
    leads to an increased volume of signals to optimise, thus improving performance.
  • Improved and new measurement – CAPI automates omnichannel measurement across web, app, and offline conversions without worry of duplicating events. It enables you to start using more sophisticated statistical analyses (e.g. market basket analysis
    and customer lifetime value).

Case studies

Let’s look at some examples of Publicis Sapient carrying out CAPI implementation.

Retail US retailer

The first case study involved working with a major US retailer. This implementation provided significant impacts on the retailer’s campaign results.

The Conversions API provided a direct and reliable connection between the marketing data from the server and Meta. Optimising the Conversions API integration helped improve the quality of event attribution and enabled higher conversion at a lower cost per result.

This advertiser achieved a 9% improvement in CPA after implementing the Conversions API via the Gateway. Alongside this, the implementation yielded the following results:

  • 7.9% more purchases were recorded
  • 46% reduction in cost per click
  • 56% increase in return on ad spend
  • Event Match Quality increased from ‘Poor’ to ‘Good’

Graphical representation of the impacts on the retailer’s campaign results after carrying out CAPI implementation

Global Fashion Retailer

In this case study Publicis Sapient worked with a German global fashion retailer. Their work produced several positive results.

The Conversions API provided a direct and reliable connection between the marketing data from the server and Meta. Optimising the Conversions API integration helped improve the quality of event attribution. It also helped to get more conversions at a lower cost per result.

After implementing the Conversions API and Meta Pixel, advertisers achieved a 13% improvement in CPC. Other benefits included:

  • Activation of the Conversion Lift.
  • A confidence level of over 99% was achieved.
  • As many as 22% more purchases were recorded.
  • Measurement optimization: Increased signals allowed ads to be delivered to the target group.

Graphical representation of the impacts on the german global fasion retailer’s campaign results after carrying out CAPI implementation

A holistic cookieless solution

CAPI is part of a wider holistic cookieless solution. We broadly see three core enablers for organisations to navigate the changing ecosystem.

  • CAPI, cookie alternatives, & foundational MarTech – Bypass 3P cookie coverage gaps by integrating conversion APIs directly with marketing platforms. Customer data technologies like CDPs enable insights and enrich models. They also allow for more effective segmentation.
  • 1P Availability & progressive consent – Modern consent management platforms (CMP) protect users’ privacy. They also provide complete control over their data through transparency, simplicity of measurement, selective engagement, and iterative consent.
  • Cross-functional partnership – Establish connections across internal Marketing, Analytics, and IT teams to enable an enterprise-wide informed approach to cookieless strategy. Integrate agency, publisher, and measurement partner POVs to relevant use case & roadmap development.

A framework for a cookieless strategy

Below is Publicis Sapient’s ‘house’ framework. As you can see, at the top of the house is the ‘vision’. This is to enable every marketer wants to build personalised experiences for customers.

Supporting our vision are three strategic pillars. The first is our media approach. We need to experiment with new ways of handling media and targeting the right people.

Next, we have our first-party data strategy. This will help our identity resolution and connect different interactions on our site.

Lastly, we want to augment our data and establish strategic partnerships. Platforms like Meta and TikTok have different ways of standing up CAPI. Partners can help us understand our consumers and improve the relevancy of our marketing.

At the bottom of the house, we have our foundations. These support our pillars and enable us to achieve our vision. Our foundations consist of:

  • The tools that we invest in to capture, organise, and enrich data.
  • The data privacy framework we develop to ensure compliance.
  • Finding cross-functional partners to help us execute our cookieless strategy.

A framework for a cookieless strategy

Prepare now

The end date for third-party cookies will arrive sooner than you expect. It’s important to start preparing for this change now before we lose our critical marketing data. Both GTM server-side & conversions API offer a clear route forward. So, why not begin building your data strategy today?

About Barbara Kalicki

Barbara Kalicki is the Manager of Data Strategy at Publicis Sapient, specializing in global data-driven transformation strategies. She has extensive experience in Google Analytics and Adobe Analytics from her previous role at InfoTrust, LLC. Barbara also has a strong background in financial services, managing web and CRM integrations, and marketing campaigns.

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Raisul Islam
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