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Differences and similarities between Google Tag Manager and gtag.js

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Tag management is an essential part of online data tracking and analysis. Two popular tools that simplify this process are Google Tag Manager (GTM) and gtag.js. Both are created by Google and are used to implement product tags such as Google Ads, Google Analytics, and Google Marketing Platform. Although they have similar functionalities, both tools present notable differences in terms of their use and capabilities. In this article, we will explore the similarities and differences between GTM and gtag.js, as well as when it is appropriate to use one or the other.

Similarities between GTM and gtag.js

  1. Both GTM and gtag.js are designed to implement Google product tags. This includes conversion tracking tags, event tracking, and more.

  2. Both tools are developed and supported by Google, ensuring reliability and compatibility with other Google services.

  3. GTM and gtag.js are designed to be interoperable. This means you can use them together or choose one over the other, depending on your specific needs.

Google Tag Manager (GTM)

GTM is a label management platform that offers the following advantages:

  • GTM is ideal when you need to manage and modify tags from multiple services, both Google and third-party, in one place. This simplifies management and maintenance.
  • Support for websites and mobile applications: GTM is versatile and can be used to manage tags in both environments, making it easy to manage tags in projects that span multiple platforms.
  • The GTM user interface is friendly and intuitive, and does not require deep technical knowledge. This allows marketing professionals and non-technical teams to efficiently implement and modify tags.
  • Collaboration and version control: GTM offers collaboration features that allow teams to work together on tag deployment. Additionally, it offers a version control system that tracks changes made, making it easy to troubleshoot and track modifications.

Google tag – gtag.js

On the other hand, gtag.js excels in specific situations:

  • This is the right choice when you need to install tags directly into your website’s source code, without using a tag management platform. This can be useful if you have specific technical requirements.
  • gtag.js allows you to work directly with tags in JavaScript, providing more granular control over their implementation. This is especially valuable for developers and technical professionals who want to precisely customize labels.


Choosing between GTM and gtag.js ultimately depends on your specific needs. If you are already using GTM and are satisfied with its functionality, there is no need to implement gtag.js, unless you have very specific technical requirements that cannot be met with GTM.

On the other hand, if you currently use gtag.js and need greater flexibility or the ability to manage multiple tags and services more efficiently, consider migrating to Google Tag Manager. GTM will allow you to simplify tag management and collaborate effectively on more complex projects.

Note that the GA4 config tag has now been automatically updated to gtag.js, so if you use those configuration tags, you are already using gtag.js effectively. This can ease the transition to more comprehensive tag management if you decide to adopt GTM in the future.