Google Tag Manager (GTM) is a free tag management tool that enables you to install, store, manage, and deploy marketing tags without modifying website code.
Marketing tags are snippets of code or tracking pixels used to track user actions and collect data. A common example is the Google tag used to install Google Analytics and other Google products. With every addition and code change, there is a risk of forgetting about breaking or losing tags.
GTM eliminates these problems by enabling you to manage, install, and deploy tags from within the software rather than in your website code. Moreover, the software injects code snippets into website code only when required. Hence, you don’t break a website by testing something.