ZeroSSL Certificate Authority
ZeroSSL offers free 90-day DV certificates via ACME and a web dashboard. Learn how ZeroSSL works and how it compares to Let's Encrypt.
ZeroSSL is a Certificate Authority operated by Stack Holdings that offers free 90-day DV SSL certificates via the ACME protocol, similar to Let's Encrypt. ZeroSSL also provides a web-based dashboard for managing certificates without ACME automation, which differentiates it from Let's Encrypt.
Free vs. Paid ZeroSSL Tiers
- Free: Up to 3 active 90-day DV certificates, managed via the web UI or ACME
- Paid plans: Unlimited certificates, 1-year validity, wildcard support, multi-domain certs
ACME Compatibility
ZeroSSL supports the standard ACME protocol, so any ACME client (Certbot, acme.sh, Caddy) can use ZeroSSL as an alternative to Let's Encrypt. The ACME directory URL is https://acme.zerossl.com/v2/DV90.
Identifying ZeroSSL Certificates
ZeroSSL certificates show O: ZeroSSL in the issuer field. The OCSP responder is at http://ocsp.zerossl.com. ZeroSSL uses Sectigo's root infrastructure — the trust chain for ZeroSSL certificates ultimately chains to a Sectigo/Comodo root certificate.
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