gtag.js (Global Site Tag) is a Google JavaScript library that makes it easier to integrate and manage various Google services on a website—particularly Google Analytics, Google Ads, and other marketing and analytics tools.
gtag.js provides a single tracking code for centrally capturing events, page views and conversions Website owners can define interactions directly in the code without having to add multiple separate tracking scripts.
Typical functions of gtag.js:
- Tracking page views
- Sending custom events (e.g. clicks and downloads)
- Setting up Conversion tracking
- Connecting multiple Google services through a single code snippet
gtag.js is Google's recommended implementation method for newer services and replaces older libraries such as analytics.js and the classic Google Ads conversion tags.
Note: Instead of adding gtag.js directly, you can also use Google Tag Manager which provides greater flexibility for managing tags.