Let’s Encrypt is a free open Certificate Authority.
https://letsencrypt.org
SSL Certificates · Root Authority
Get access to data on 39,285,335 websites that are LetsEncrypt Customers. We know of 2,000,001 live websites using LetsEncrypt and an additional 37,285,334 sites that used LetsEncrypt historically and 1,215,832 websites in the United States.
Get a list of 39,285,335 websites using LetsEncrypt which includes location information, hosting data, contact details, 3,068,921 currently live websites which includes 1,068,920 domains that redirect to sites in the list. 37,285,334 sites that used this technology previously and 1,215,832 websites in the United States currently using LetsEncrypt.