Client-side tagging vs. server-side tagging

Client-side tagging vs. Server-side tagging – A brief comparison

Before we discuss about client-side tagging and server-side tagging, let’s briefly understand what is a tag. 

What is a tag? How does it work?  

Tag is a code snippet that is placed on different digital properties to track an event. Originally, the job of a tag was to identify a digital property and be used to retrieve it during a search. Over the years, marketers have started using tags to track specific events, assets, or activities associated with customers and media channels for better analytics and insights. Tags can be either image pixels and JavaScript tags

The collected data can in turn be used for personalizing the user experience, retargeting via ads, etc. Most websites currently can deploy hundreds of third-party tags which help companies with a better understanding of their visitors by providing identity and analytics. The frequency, amount, and type of data collected by such third-party tags cannot be governed or controlled by the digital property owners. These third-party tags end up capturing a lot of Personally Identifiable Information (PII) of the users making them susceptible to potential data leaks and may be resold to other data brokers.   

tag management solution (TMS) simplifies tag implementation across different digital properties such as your website, videos, emails, products, apps, and e-stores. Traditionally, most of the tagging was done through client-side Tag Managers.  

Users have become more conscious about their data being collected, used, and sold. Companies started looking for solutions that can help govern their user data collection process and subsequent usage.  

Several prominent browsers such as Firefox, Safari, Brave, and Edge have incrementally made it difficult for third-party tracking. They have disabled cross-site tracking and limited the duration of third-party cookies. With third-party cookies set to be disbanded in the coming months, marketers have had to switch to first-party data collection to minimize disruption of day-to-day marketing activities.  

What is client-side tagging?  

As the name should suggest, this form of tagging relies on the client or user, precisely their browser. When a user visits a web page, the tags embedded in the code are fired. During that time, the code is parsed by the browser and then the information is sent across to the vendors (third-parties) who have their tags deployed on the site.  

With Client-side Tagging, companies did not require any complex infrastructure setup. The third-party companies did most of the heavy lifting in return for access to user data.  From a marketer’s standpoint, ease of use and deployment were the key to client-side tagging. However, it has its drawbacks.  

With the users’ browser doing the bulk of work in terms of data sharing, no wonder it was widely used by third-party vendors to monitor user behavior and collect data. This led to security and privacy concerns. These third-party tags often don’t have proper documentation and often end up collecting a lot of PII of users than necessary.  

An added challenge is that the same data could also be accessed by other tags or trackers. Third-party cookies allowed companies to track user behavior across multiple websites.  Some of the biggest concerns in client-side tagging are privacy, the flow of data, and data leaks. 


What is server-side tagging?  

The solution to the shortcomings of client-side tag managers is server-side tagging. Rather than data flowing from the users’ browser to 3rd party systems, a single API call is made to the Server-side Tag manager. The data in turn flows from Server-side Tag Manager to 3rd party servers. Before the data flows to 3rd party vendors, companies can determine what data goes out. You can remove PII before sending data, and stop sending data if the user has declined consent. 

Why companies are switching to server-side tagging?  

Brands are looking towards a secure data collection method. A first-party data strategy can help protect your users while collecting data required to offer personalization at scale.  

According to various research published by GoogleAmazon, and Akamai, sites that load faster have less churn, increase trust in the brand. Since the number of network calls from the end user’s browser is drastically reduced, web pages load faster as well. This helps improve the end-user experience. In client-side tag managers, the browser is responsible for most of the heavy lifting. With server-side tag managers, this work gets offloaded to the server.  

Primary differences between client and server-side tagging 

Viewing from a broad perspective, both these tagging infrastructures differ a lot. 

Client-side tagging (CST) Server-side tagging (SST) 
Security Low High 
Privacy Law Compliance Difficult to comply Easy to comply 
Implementation Easy Moderate 
Free / Paid Free (offered by most vendors) Paid 
Website performance Slow Fast 
Data loss due to Adblockers Yes No 
Ease of protecting user PII Very difficult Yes 
Visitor Identity Easily provided by 3rd party providers Companies have to build first-party identity in-house 


There is a one-time implementation switch that needs to be done to transition from client-side to server-side. From a long-term marketing data collection, Brand protection, and future proofing standpoint, companies will have to invest in Server-side Tagging

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