Find every subdomain
of a domain.

Every hostname under a domain that ever appeared in a public TLS certificate — with certificate counts and first/last seen dates.

1 host · 200 ms

HostCertsFirst seenLast seen
safeopt.co 8 2026-06-01 2026-09-29

Programmatic access: API GET /v1/hosts/safeopt.co (API key for paging).

Shown here: hostnames with a certificate that is valid now or expired within the last 90 days. The full history since 2013 — hostnames whose last certificate expired earlier — is a Pro plan method: GET /v1/hosts-history/safeopt.co.