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.

5 hosts · 287 ms

HostCertsFirst seenLast seenDNS
kctool.com 6 2026-06-03 2026-10-01 ok
*.kctool.com 1 2026-01-28 2026-01-28 —
newsletter.kctool.com 4 2026-04-18 2026-08-15 ok
account.kctool.com 5 2026-06-05 2026-10-03 ok
www.kctool.com 4 2026-06-04 2026-10-02 ok

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