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.

2 hosts · 239 ms

HostCertsFirst seenLast seen
safeoptmail.com 8 2026-06-01 2026-09-29
uptime.safeoptmail.com 5 2026-05-12 2026-09-09

Programmatic access: API GET /v1/hosts/safeoptmail.com (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/safeoptmail.com.