v2 of the Google reCAPTCHA system.
https://developers.google.com/recaptcha/docs/display
Widgets
Get access to data on 3,648,101 websites that are reCAPTCHA v2 Customers. We know of 1,986,314 live websites using reCAPTCHA v2 and an additional 1,661,787 sites that used reCAPTCHA v2 historically and 1,146,457 websites in the United States.
Get a list of 3,648,101 websites using reCAPTCHA v2 which includes location information, hosting data, contact details, 1,986,314 currently live websites and an additional 1,797,071 domains that redirect to sites in this list. 1,661,787 sites that used this technology previously and 1,146,457 websites in the United States currently using reCAPTCHA v2.