v2 of the Google reCAPTCHA system.
https://developers.google.com/recaptcha/docs/display
Widgets
Get access to data on 3,389,682 websites that are reCAPTCHA v2 Customers. We know of 2,029,524 live websites using reCAPTCHA v2 and an additional 1,360,158 sites that used reCAPTCHA v2 historically and 1,165,948 websites in the United States.
Get a list of 3,389,682 websites using reCAPTCHA v2 which includes location information, hosting data, contact details, 2,029,524 currently live websites and an additional 1,715,868 domains that redirect to sites in this list. 1,360,158 sites that used this technology previously and 1,165,948 websites in the United States currently using reCAPTCHA v2.