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.

2 hosts · 227 ms

HostCertsFirst seenLast seenDNS
sectigotestcerts.com 38 2026-03-12 2026-09-18 nodata
www.sectigotestcerts.com 5 2026-03-12 2026-07-20 nxdomain

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