What is Server-Side Tracking? A simple Explanation

This page is for anyone curious to learn what server-side tracking—or server-side tagging, also known as serverside tracking—really means. I understand that the distinctions between server-side and client-side, as well as terms like tagging and tracking, can be confusing. Don’t worry—my goal is to bring clarity to these concepts and explain them as simply as possible.

What is server-side tracking?

Server-side tracking is a method of web tracking where the processing of tracking data occurs on your own server. Let me refer back to the example of sewing machines I used when explaining client-side tracking (read more here).

Imagine a user picks up their phone and searches for sewing machines in their browser. By chance, you’re a sewing machine provider with a great website featuring a wide range of models. This user visits your website to compare various products, perhaps with specific features in mind. They click on different sewing machines and compare their features. The user might even click a button (e.g., “Add to Cart”) and potentially complete a purchase. During this session, multiple interactions occur between the user and your website, which you might want to analyze using tools like Google Analytics.

Each interaction the user has with your site (page views, scroll depth, clicked buttons, etc.) is tracked. These data points are loaded into a tag manager script that’s triggered by the user’s visit. This script then loads further tracking scripts, which are sent to your server for processing.

Figure: The server-side tracking process

Note: With server-side tracking, the collection, processing, and forwarding of data are managed through a tool known as the server tag manager.

What is the Role of the Server in Server-Side Tracking?

As mentioned, server-side tracking involves a server. This server, hosted in a cloud environment or another setup, acts as a central control hub where you maintain full control over your data. Google, for instance, provides an option to host a server on Google Cloud. In addition, Google offers the server tag manager, which enables you to route data to your server.

This means that when a user searching for sewing machines visits your website, it triggers the tag manager script. This script then sends data (about the user’s interactions with your website) to your server via the server tag manager. On your server, you can view, enrich, validate, or remove data, deciding which data to forward to third parties like Google Analytics.

Why Do I Need a Server Tag Manager?

Imagine you place a server between your website and third parties like Google Analytics. You’ll need a tool to forward the collected data from the tag manager script to your server; otherwise, you’ll have a server with no data flow. The server tag manager acts as an intermediary between the data collected on your website and your server, ensuring that data flows correctly. Without a server tag manager, you wouldn’t be able to send data to third-party providers like Google Analytics, and consequently, all collected data would be lost.

What are the Alternatives?

Server-side tracking or server-side tagging?

You might feel as I do—that there’s a lot of confusion about the terms Server Side Tracking and Server Side Tagging, and the differences are not clearly defined. However, I couldn’t identify any notable difference between them, which leads me to believe they refer to the same method. Let me explain further.

Regardless of which term you search for on Google, all providers of this method discuss the integration of a server using a Server Tag Manager, specifically the Google Tag Manager (GTM). I suspect the term server-side tagging was coined and popularized by Google, given its use of the word “Tag.” Google could have used “Track” instead but likely opted for “Tag” for tonal reasons. Fundamentally, there are two methods to distinguish: client-side tracking and server-side tracking; whether you call them Tracking or Tagging is unimportant. What matters is understanding that both methods use Google’s tag management systems, namely Google Tag Manager (GTM). With client-side tracking, you use the Web Tag Manager to load a web container, while with server-side tracking, you use the Server Tag Manager, which loads a server container. Both tag management systems are part of Google Tag Manager (GTM).

The Classic Tracking Method: Client-Side Tracking

The simplest form of web tracking is the client-side tracking method. Let’s recall the sewing machine example. Here, when the website is accessed, a Tag Manager script is loaded, which in turn loads additional tracking scripts that are then forwarded to third-party providers. You may have already noticed that in this setup, there is no server positioned between the website and third-party providers. This is the key difference from server-side tracking. In client-side tracking, data processing occurs in the browser rather than on a dedicated server, as in server-side tracking. So instead of using Google’s Server Tag Manager, you use the Web Tag Manager.

Figure: The client-side tracking process

Note: Client-side tracking occurs in the user’s browser (client) and not on a server. The collected data is then sent directly to third-party providers like Google Analytics.

What is a Tag Manager?

There are two versions of Tag Management Systems: the Web Tag Manager and the Server Tag Manager. Both represent the Google Tag Manager (GTM), but the Web Tag Manager operates with a web container in the user’s browser (client), while the Server Tag Manager operates with a server container on a server. This means that Google Tag Manager (GTM) describes different types of Tag Management Systems. With it, you can track specific events relevant to your business. For example, if you use the Tag Manager, you can configure events beyond the predefined events in Google Analytics reports. You might, for instance, want to measure your visitors' scroll depth and set up a tag with specific triggers that activate when the visitor reaches a scroll depth of 25%, 50%, or 75%.

Note: A Tag Management System (TMS), like Google Tag Manager (GTM), is a tool that allows you to configure and manage tags easily. It enables efficient embedding of third-party tracking scripts on websites without needing to directly alter website code.

So, what are Tags and Triggers?

With tags, you specify within the Tag Manager which events you want to track, such as scroll depth, as mentioned. Then, you need to define the actions that trigger this tag (event)—this is where triggers come in. Triggers specify the actions that must occur for the tag (event) to activate. For example, you might set scroll depths as the condition for activation, so the tag will trigger when a visitor reaches 25%, 50%, or 75% scroll depth.

Note: Tags are configuration elements within a Tag Management System that control which tracking data is collected and to which systems it should be sent. They define what information is collected during specific events.

Triggers, on the other hand, determine when a tag should activate. They set specific conditions that must be met for a tag to be activated, such as when a user visits a particular page or scrolls to a certain point.

What are Web and Server Containers?

A web container is a script that runs in the browser to collect tracking data and send it to third-party providers. This process is managed through a Web Tag Manager from Google, specifically the Google Tag Manager (GTM). A server container, on the other hand, is a server-side environment that receives tracking requests from the browser and processes them further. This process is facilitated by a Server Tag Manager, also part of Google Tag Manager (GTM), which routes tracking requests to your own server.

Which Approach Is Recommended? 

The choice between client-side tracking and server-side tracking depends on a company’s specific needs and objectives. Both methods have their pros and cons, which we’ll examine in detail.

Advantages of Server-Side Tracking in Detail

Enhanced Data Control and Quality with Improved Data Security

A significant advantage of server-side tracking is the increased control over collected data. Since all tracking data is processed on a company’s server first, companies can decide which data to forward to third-party providers and which to withhold. This substantially reduces reliance on third-party providers. Additionally, server-side tracking offers substantial benefits in terms of data security and GDPR compliance, as sensitive user data, such as IP addresses or email addresses, can be anonymized or removed on the company’s server before being forwarded to external services. Overall, companies can expand their data set with server-side tracking, as no data is lost within the user’s browser, and even if a user declines the cookie banner, data is preserved in an anonymized or pseudonymized form (you can read more avout tracking without consent here). This enables a nearly complete data set when personal information is removed upon cookie banner rejection, and browser restrictions are bypassed.

Bypassing Browser Tracking Prevention Mechanisms (e.g., Safari's ITP)

Another advantage is the ability to bypass browser tracking prevention mechanisms. Browser extensions like ad blockers or the privacy features of modern browsers often block or restrict client-side tracking, as browsers are configured to prohibit third-party tracking. Since communication with server-side tracking primarily occurs between your own server and third-party providers, these tracking measures are less vulnerable to such blocks. 

Figure: Advantages of server-side tracking

Additionally, server-side tracking offers benefits in terms of reduced webpage load times, positively impacting SEO. This is because fewer tracking scripts are run in the user's browser (client), leading to better performance.

What are the Advantages of Client-Side Tracking?

Easy Implementation and Lower Complexity

One of the key advantages of client-side tracking is the ease of implementation and management. Most Tag Manager solutions, such as Google Tag Manager, provide user-friendly interfaces that allow for configuring tags and triggers without needing deep technical expertise.

Comparison of both Tracking Methods

The main difference between client-side tracking and server-side tracking lies in where the tracking data is processed and how much control companies have over the data collected.

• Processing Location: With client-side tracking, all tracking data processing occurs directly in the user’s browser. This means that tracking scripts load in the browser, and all interactions like page views, clicks, or scroll depth are sent directly to third-party providers. In contrast, with server-side tracking, tracking data is first sent to the company’s server, where a server tag manager processes the data before forwarding it to third parties. As a result, data remains within the company’s control before being shared externally.

• Data Control: One of the main advantages of server-side tracking is greater control over collected data. Since data is processed on the company’s server first, companies can decide which information to forward to third-party providers and which to withhold. Sensitive data, such as IP addresses, can be anonymized or completely removed before sharing with third parties. In client-side tracking, this level of control is lacking, as tracking scripts run directly in the user’s browser, and data is sent to third parties without any intermediary step.

• Privacy and GDPR Compliance: Server-side tracking provides better compliance with GDPR requirements, as data processing occurs on a company’s own server. With options for anonymizing or pseudonymizing personal data, companies can ensure that sensitive information is not passed to third-party providers without protection. In client-side tracking, data is directly accessible to third parties, making it harder to ensure full compliance with privacy requirements.

• Susceptibility to Tracking Blockers: Client-side tracking is vulnerable to browser extensions like ad blockers and privacy features in modern browsers, which can block tracking scripts or prevent cookie storage. With server-side tracking, communication with third parties is managed via the company’s server, which allows most of these blocks to be bypassed, ensuring more reliable data capture.

• Website Performance: Because all tracking scripts load in the browser with client-side tracking, this can negatively impact webpage load times. Server-side tracking, however, requires fewer scripts in the user’s browser, as most requests are processed server-side, leading to better performance and faster load times.

• Implementation and Complexity: Implementing client-side tracking is generally simpler and requires less technical expertise. Tools like Google Tag Manager provide user-friendly interfaces for quickly and easily configuring tags and triggers. Server-side tracking, however, is more complex and requires technical expertise and a suitable server infrastructure, resulting in higher costs and more management requirements.

So, which is better?

There’s no one-size-fits-all answer to this question, as each tracking method suits different scenarios. If you’re a small business and primarily want to analyze data in Google Analytics and occasionally invest a few hundred euros in SEA campaigns, server-side tracking might not be worthwhile. Why? Because the effort involved is too high. Hosting a server and implementing server-side tracking often requires a budget, and, simply put, the costs may outweigh the benefits in this case. However, if you’re investing in marketing campaigns, the added effort is worth it since you gain full control over your data, allowing you to build a more complete dataset for data-driven decisions that significantly impact your goals.

Regardless of budget, server-side tracking is recommended for companies that prioritize a complete dataset, data security, and privacy compliance. Client-side tracking is better suited for scenarios where a quick and cost-effective implementation is necessary, as it’s much simpler to set up and doesn’t require extensive technical knowledge. For companies that lack the resources to manage a server or for smaller projects where data control is less critical, client-side tracking may be sufficient.

Conclusion

In summary, client-side tracking is a straightforward and easy-to-implement method for collecting tracking data, but it’s susceptible to limitations from ad blockers and privacy protections. Server-side tracking, on the other hand, offers greater control over data, improved privacy options, and more reliable data capture, though it requires more technical knowledge and a more complex infrastructure. Companies that place a high value on data security and privacy should consider server-side tracking to fully benefit from enhanced control and compliance with GDPR standards.