Let’s Encrypt is a free open Certificate Authority.
https://letsencrypt.org
SSL Certificates · Root Authority
Get access to data on 42,190,480 websites that are LetsEncrypt Customers. We know of 2,000,001 live websites using LetsEncrypt and an additional 40,190,479 sites that used LetsEncrypt historically and 1,160,143 websites in the United States.
Get a list of 42,190,480 websites using LetsEncrypt which includes location information, hosting data, contact details, 2,000,001 currently live websites and an additional 1,005,842 domains that redirect to sites in this list. 40,190,479 sites that used this technology previously and 1,160,143 websites in the United States currently using LetsEncrypt.