Twitter ads conversion tracking code.
https://business.twitter.com/en/help/campaign-measurement-and-analytics/conversion-tracking-for-websites.html
Analytics and Tracking · Conversion Optimization
Get access to data on 541,355 websites that are Twitter Conversion Tracking Customers. We know of 75,749 live websites using Twitter Conversion Tracking and an additional 465,606 sites that used Twitter Conversion Tracking historically and 34,846 websites in the United States.
Get a list of 541,355 websites using Twitter Conversion Tracking which includes location information, hosting data, contact details, 75,749 currently live websites and an additional 523,725 domains that redirect to sites in this list. 465,606 sites that used this technology previously and 34,846 websites in the United States currently using Twitter Conversion Tracking.