Google Tag Manager

Google Tag Manager is a tag management system from Google: a tool for setting up and managing tags on a website or app without changing the site's code. A tag is a small piece of code from an analytics or advertising service, such as Google Analytics or Google Ads, that sends data about visits to that service.

The site owner adds two snippets of code to each page once. After that, all tags are managed in Tag Manager's web interface: the owner sets up tags, triggers that make a tag fire when certain events occur, and variables that hold values used by the tags. The tags, triggers and variables of one site or app form a container. Tags load asynchronously, so they do not slow down the page. Templates cover third-party vendor tags, a preview mode shows changes before they go live, and workspaces and access controls let marketing and IT teams work together. Server-side tagging moves third-party tags off the site into a server container in the owner's Google Cloud account.

Tag Manager is free. Tag Manager 360 is a separate enterprise version.