DigiCert is one of the world's largest enterprise certificate authorities with ~35% market share, serving 80%+ of the Fortune 100. It offers DV/OV/EV SSL/TLS certificates, code signing, and PKI solutions, known for its powerful CertCentral management platform and API automation.
Let's Encrypt is the world's largest free, open certificate authority operated by ISRG, serving 300M+ active websites with 70%+ of global CA issuance. Uses the ACME protocol for fully automated 90-day DV TLS certificate lifecycle management.
Founded in 1996, GlobalSign is one of the world's longest-running commercial CAs serving 150+ countries. Offers full SSL/TLS certificates, enterprise managed PKI, IoT device identity, and document signing solutions.
GlobalSign SSL is the SSL certificate product line of GlobalSign (GMO Group Japan), founded in 1996. It issues 100,000+ certificates daily with Atlas management platform and ACME auto-renewal, leading the IoT device certificate segment.
Entrust SSL is the SSL/TLS certificate product line of Entrust (founded 1994, Minneapolis MN USA). All certificates are signed via FIPS 140-2 Level 3 nShield HSM, serving 150+ countries as the preferred SSL solution for government and financial institutions.
AlphaSSL is GlobalSign's entry-level SSL certificate brand, providing DV and OV certificates backed by GlobalSign's root trust, with prices from $49.95/year for fast HTTPS deployment.
Comodo SSL is a globally recognized budget SSL certificate brand whose CA business merged into Sectigo, with over 100 million certificates issued and PositiveSSL DV from $5/year.
Buypass is a Norway-based Certificate Authority (founded 1968) offering free 180-day SSL certificates via ACME automation, alongside the Norwegian government e-ID system (Buypass ID) and eIDAS-qualified digital signatures.
Founded in 2003, CAcert is a community-driven open-source certificate authority offering free SSL/TLS server certificates, code signing certificates, and email certificates with fully transparent operations.