In the world of digital marketing, data reliability and privacy compliance have become key challenges for advertisers. Changes in browsers, the growing use of ad blockers, and increasingly strict GDPR regulations significantly affect the quality of data collected by websites. Therefore, the way data is collected and sent to platforms (such as Google, Facebook, and TikTok) is more important than ever.
Google Tag Manager (GTM) today offers three main approaches: Client-side, Google Tag Gateway (GTG), and Server-side (sGTM). Each has its own purpose, level of control, and implementation cost. Below is an overview of the main differences, advantages, and recommendations for each option.
Client-side GTM – The Classic Tracking Method
Client-side GTM is the most commonly used and simplest tracking setup. All tags (e.g., Google Analytics, Meta Pixel, TikTok Pixel) are loaded directly in the user’s browser.
Advantages:
- Quick and easy implementation.
- No additional costs.
- Supports all advertising platforms.
Limitations:
- Data is sent as third-party requests, making it vulnerable to blocking by browsers and ad blockers.
- Measurement accuracy is reduced.
- Limited GDPR compliance, as cookies and data are sent directly to external platforms.
Client-side is the most basic but also the most vulnerable tracking approach.
Google Tag Gateway (GTG) – A First-party Layer for Google Tools
Google Tag Gateway is a more modern approach that allows Google data to pass through your own domain before reaching Google services. In practice, this means your domain intermediates in sending data to Google.
Advantages:
- Improved measurement accuracy – Google Analytics and Google Ads signals are sent through your domain.
- Better resistance to ad blockers and ITP – requests appear as first-party traffic.
- Enhanced GDPR compliance – GTG uses more accurate consent signals.
- No additional cost – does not require a dedicated server.
Limitations:
- Only Google platforms (GA4, Google Ads, Floodlight) run through the first-party layer.
- Other platforms (Meta, TikTok, LinkedIn) remain client-side.
- Limited control over data (the proxy forwards data but does not allow filtering).
GTG is an optimal solution for small and medium websites that want more accurate tracking without additional costs. It is often used as a transitional step toward server-side implementation, as it shares similar first-party logic.
Server-side GTM – Advanced Tracking via Your Own Server
Server-side implementation (sGTM) represents the highest standard of data tracking. Data from the website is first sent to your own server, where it can be filtered, processed, and anonymized before being sent to advertising platforms.
Advantages:
- Very high measurement accuracy – all data passes through a controlled server environment.
- Resistant to ad blockers – endpoints are unrecognizable to blockers.
- Full control and security – every signal can be filtered, customized, and anonymized.
- Full GDPR compliance.
- Advanced integrations with multiple advertising and analytics systems.
Limitations:
- Requires server hosting and technical setup.
- Needs more time and expertise to implement.
Server-side GTM is recommended for advanced clients seeking full control and long-term data stability.
Which GTM approach should you choose?
If you are just setting up tracking and need a simple, entry-level solution, Client-side GTM is sufficient. It allows fast deployment and basic metric tracking without additional investment, making it ideal for smaller websites and early-stage projects.
For those who want more reliable Google data and to avoid measurement loss caused by ad blockers or ITP restrictions without investing in a server, Google Tag Gateway (GTG) is the best choice. It represents the first step toward a first-party approach, improving data quality while remaining easy to manage.
If your goal is complete data control, higher accuracy, and long-term stability, Server-side GTM is recommended. This approach allows advanced filtering and anonymization of data as well as integration with multiple advertising platforms, making it ideal for mature and growing digital systems.
Conclusion
The shift toward first-party and server-side models is no longer optional but essential. Given the ongoing changes in privacy and technology, businesses that adopt modern approaches such as GTG or Server-side GTM earlier will benefit from more reliable data, better ad optimization, and a stronger competitive advantage. In practice, every company should progress step by step – from basic tracking toward systems that ensure greater control, accuracy, and data security.
