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 581,956 websites that are Twitter Conversion Tracking Customers. We know of 84,797 live websites using Twitter Conversion Tracking and an additional 497,159 sites that used Twitter Conversion Tracking historically and 57,206 websites in the United States.
Get a list of 581,956 websites using Twitter Conversion Tracking which includes location information, hosting data, contact details, 84,797 currently live websites and an additional 524,098 domains that redirect to sites in this list. 497,159 sites that used this technology previously and 57,206 websites in the United States currently using Twitter Conversion Tracking.