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 529,680 websites that are Twitter Conversion Tracking Customers. We know of 81,198 live websites using Twitter Conversion Tracking and an additional 448,482 sites that used Twitter Conversion Tracking historically and 37,410 websites in the United States.
Get a list of 529,680 websites using Twitter Conversion Tracking which includes location information, hosting data, contact details, 293,524 currently live websites which includes 212,326 domains that redirect to sites in the list. 448,482 sites that used this technology previously and 37,410 websites in the United States currently using Twitter Conversion Tracking.