Certum vs ZeroSSL

ZeroSSL is used by more websites in our catalog: 579 use Certum and 2,425 use ZeroSSL.

Certum sites have the higher median Ahrefs Domain Rating (Certum: 55, ZeroSSL: 23).

Between 2026-06 and 2026-07, Certum went from 0.08% to 0.07% of all tracked sites, while ZeroSSL went from 0.29% to 0.28%. Certum is gaining ground faster in our index.

No. A site runs a single SSL certificate authority, so Certum and ZeroSSL are mutually exclusive.

Adoption is counted from Site Stats Database's own crawl; Domain Rating comes from Ahrefs and traffic from DataForSEO. Figures reflect the sites we track and refresh at least monthly.