Tag Manager and gtag.js

Google Tag Manager and the global site tag (gtag.js) are both fully supported methods for the deployment of tags for Google products, such as Google Ads and Google Marketing Platform. If you are trying to decide between Tag Manager and gtag.js, then this document is for you.

Both Tag Manager and gtag.js perform similar functions:

Tag Manager is a tag management system that allows you to quickly and easily update tags on your website or mobile app from a web interface.
gtag.js is the JavaScript framework that is used to add Google tags directly to web pages.

Both solutions are built on the same core Google infrastructure, and are interoperable. You are free to choose the solution that best suits your needs.

Consider Tag Manager if you need:

The ability to deploy and modify both Google and 3rd party tags
The ability to deploy and modify tags for both web and mobile apps
The ability to deploy and modify tags on the fly from a web interface
Collaboration and versioning capabilities

Consider gtag.js if you are unable to use Google Tag Manager, or the following capabilities are important to you:

The ability to install tags directly on your web page, without the ramp-up time of setting up a tag management system
The ability to work with your tags directly in JavaScript without being required to work with a separate interface

If you currently use Tag Manager, you should continue to do so. Google Ads and Google Marketing Platform tags are fully supported by Tag Manager, and there is no need to deploy additional gtag.js-based code on your site if Tag Manager is already in use.

If you're already using gtag.js, you can always upgrade to Tag Manager at a later date.

Note: You should not use the custom HTML tag option to deploy gtag.js-based tags. Instead, use Tag Manager's native tag templates for Google Ads, Analytics, and Floodlight.