Find every subdomain
of a domain.

Every hostname under a domain that ever appeared in a public TLS certificate — with certificate counts and first/last seen dates.

6 hosts · 307 ms

HostCertsFirst seenLast seen
duckhead.com 19 2026-04-19 2026-10-02
mta-sts.send.duckhead.com 4 2026-04-27 2026-07-19
returns.duckhead.com 20 2026-05-16 2026-09-11
mta-sts.duckhead.com 4 2026-05-04 2026-07-26
account.duckhead.com 13 2026-04-26 2026-09-06
www.duckhead.com 13 2026-05-16 2026-09-26

Programmatic access: API GET /v1/hosts/duckhead.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/duckhead.com.