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 · 299 ms

HostCertsFirst seenLast seenDNS
cynetsystems.com 22 2026-04-30 2026-09-29 ok
*.cynetsystems.com 7 2026-06-02 2026-09-29 —
unsubscribe.cynetsystems.com 5 2026-04-26 2026-08-25 ok
helpdesk.cynetsystems.com 10 2026-05-12 2026-09-08 ok
jobs.cynetsystems.com 5 2026-05-12 2026-09-11 ok
medjobs.cynetsystems.com 5 2026-05-02 2026-09-01 ok
rewards.cynetsystems.com 5 2026-05-06 2026-09-05 ok
www.cynetsystems.com 12 2026-05-01 2026-08-27 ok

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