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.

3 hosts · 280 ms

HostCertsFirst seenLast seenDNS
rdttech.co 14 2026-05-10 2026-10-01 ok
*.rdttech.co 10 2026-06-05 2026-10-01 —
www.rdttech.co 2 2026-05-10 2026-05-10 ok

Programmatic access, with DNS A records: API GET /v1/hosts/rdttech.co (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/rdttech.co.