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 62,721,222 websites Global Site Tag Customers. We know of 33,996,182 live websites using Global Site Tag and an additional 28,725,040 sites that used Global Site Tag historically and 3,636,627 websites in the United States.
Get a list of 62,721,222 websites using Global Site Tag which includes location information, hosting data, contact details, 33,996,182 currently live websites and an additional 5,286,670 domains that redirect to sites in this list. 28,725,040 sites that used this technology previouslyand 3,636,627 websites in the United States currently using Global Site Tag.
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