Google's primary tag for Google Measurement/Conversion Tracking, Adwords and DoubleClick.
https://support.google.com/adwords/answer/7548399
Analytics and Tracking
Get access to data on 44,983,135 websites Global Site Tag Customers. We know of 24,673,610 live websites using Global Site Tag and an additional 20,309,525 sites that used Global Site Tag historically and 3,271,113 websites in the United States.
Get a list of 44,983,135 websites using Global Site Tag which includes location information, hosting data, contact details, 24,673,610 currently live websites and an additional 4,613,827 domains that redirect to sites in this list. 20,309,525 sites that used this technology previouslyand 3,271,113 websites in the United States currently using Global Site Tag.
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