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.

8 hosts · 260 ms

HostCertsFirst seenLast seen
nipsco.com 3 2026-03-18 2026-09-25
cdrstage.nipsco.com 2 2026-03-31 2026-08-26
srm.nipsco.com 1 2026-06-24 2026-06-24
cdrstage-srm.nipsco.com 1 2026-07-07 2026-07-07
go.nipsco.com 3 2026-06-02 2026-08-10
myaccount.nipsco.com 3 2026-03-18 2026-09-25
cdrstage-myaccount.nipsco.com 2 2026-03-31 2026-08-26
www.nipsco.com 3 2026-03-18 2026-09-25

Programmatic access: API GET /v1/hosts/nipsco.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/nipsco.com.