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.

10 hosts · 339 ms

HostCertsFirst seenLast seenDNS
firmspace.com 5 2026-04-16 2026-10-07 ok
book.firmspace.com 5 2026-05-13 2026-09-11 ok
helpdesk.firmspace.com 10 2026-06-01 2026-09-29 ok
elink3f3.mail.firmspace.com 2 2026-08-20 2026-08-20 ok
atxmail.firmspace.com 5 2026-05-04 2026-09-01 ok
crm.firmspace.com 11 2026-05-29 2026-09-27 ok
hq.firmspace.com 5 2026-05-15 2026-09-16 ok
member.firmspace.com 14 2026-05-29 2026-09-24 ok
support.firmspace.com 1 2026-01-09 2026-01-09 nxdomain
www.firmspace.com 5 2026-06-04 2026-09-17 ok

Programmatic access, with DNS A records: API GET /v1/hosts/firmspace.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/firmspace.com.