The world of digital marketing and analytics is changing rapidly. Where we previously relied blindly on traditional measurement methods, privacy legislation and browser restrictions are forcing us towards a new standard. The big question now: do you stick with Client-Side tracking or switch to Server-Side Google Tag Manager (GTM)?

In this article, we explain the crucial differences so that you can make the right choice for your data strategy.

What is Client-Side GTM? (The traditional way)

With Client-Side tracking, all interaction takes place in the visitor's browser (the 'client'). When someone clicks on your website, the browser sends that data directly to platforms such as Google Analytics, Facebook (Meta), or LinkedIn.

How it works: Data is sent directly from the browser to external marketing vendors.
Load: Multiple tags from different parties must load simultaneously, which places a heavier load on the visitor's browser.
Control: You have less direct control over exactly which specific data these third parties collect and what their impact is on privacy.

What is Server-Side GTM? (The new standard)

With Server-Side tracking, your own secure server acts as an intermediary. The browser sends the data to your server, and only then do you decide which anonymized data is forwarded to the advertising platforms.

Security: Data is first sent to your own secure server environment before going anywhere else.
Privacy: Data can be filtered and anonymized on the server (for example, by removing IP addresses) before being sent to third parties.
Performance: Because the browser only needs to send one request to your server instead of ten requests to different vendors, browser performance improves significantly.
Reliability: Server-side tracking helps bypass ad blockers and extends the lifespan of cookies, resulting in a higher 'User Trust Score' and more accurate data.

Comparison at a glance

Feature	Client-Side GTM	Server-Side GTM
Data transmission	Directly to third parties	Via our own secure server
Browser load	High (multiple tags)	Layer (one data stream)
Privacy check	Limited	Complete control (filtering)
Adblockers	Often blocked	More resistant to blockages

Which one should you choose?

Although Client-Side GTM is simpler and cheaper to set up, Server-Side GTM is essential for companies that take privacy and data quality seriously. It offers the necessary protection against stricter browser regulations (such as ITP) and ensures that your marketing budget is used more effectively based on clean data.