Find every subdomain
of a domain.

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

3 hosts · 386 ms

HostCertsFirst seenLast seenDNS
fpchq.org 6 2026-04-17 2026-10-01 ok
mta-sts.fpchq.org 6 2026-05-20 2026-09-17 ok
www.fpchq.org 6 2026-04-17 2026-10-01 ok

Programmatic access, with DNS A records: API GET /v1/hosts/fpchq.org (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/fpchq.org.