Google Tag Manager (GTM)

Google Tag Manager (GTM) is a free tag management system developed by Google that allows marketers and developers to add, update, and manage marketing and analytics tags (JavaScript and HTML snippets) on a website without modifying the site's source code. It centralizes tag deployment through a web-based interface with built-in version control.

GTM is used to deploy Google Analytics 4, Google Ads conversion tracking, Facebook Pixel, Hotjar, and hundreds of other third-party tags. Screaming Frog can audit GTM implementations, and Google Tag Assistant (Chrome extension) validates that tags fire correctly. Improper GTM configuration can lead to slow page speeds tracked via Lighthouse.