analytics-dictionary / term / tracking & measurement
gtag.js
gtag.js is the Google tag, a JavaScript library that sends data to Google Analytics, Google Ads and other Google products.
Written by Reflective Data experts · updated Oct 5, 2026
You can add it directly to your pages or load it through a tag manager. It is configured with measurement IDs and sends events to the connected products.
Many sites run both gtag.js and Google Tag Manager by accident, which leads to duplicate hits. Pick one deployment method per tag.
related
EventGoogle Analytics (GA4)Google Tag Manager
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