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.

6 hosts · 324 ms

HostCertsFirst seenLast seenDNS
rkc.edu 55 2026-04-12 2026-10-03 ok
*.rkc.edu 43 2026-04-28 2026-10-03 —
salford.rkc.edu 24 2026-04-12 2026-09-22 ok
www.salford.rkc.edu 17 2026-04-12 2026-09-22 ok
campus.rkc.edu 8 2026-05-02 2026-08-31 ok
www.rkc.edu 12 2026-04-12 2026-08-23 ok

Programmatic access, with DNS A records: API GET /v1/hosts/rkc.edu (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/rkc.edu.