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.

8 hosts · 255 ms

HostCertsFirst seenLast seenDNS
helenplum.org 4 2026-04-15 2026-08-12 ok
sierra.helenplum.org 4 2026-06-07 2026-10-05 ok
fmi-marc.helenplum.org 5 2026-05-10 2026-09-07 ok
catalog.helenplum.org 13 2026-04-16 2026-09-25 ok
go.helenplum.org 5 2026-05-29 2026-09-26 ok
www.helenplum.org 4 2026-04-15 2026-08-12 ok
ezproxy.helenplum.org 10 2026-04-29 2026-09-26 ok
*.ezproxy.helenplum.org 10 2026-04-29 2026-09-26 —

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