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.

4 hosts · 167 ms

HostCertsFirst seenLast seen
happymammoth.co 14 2026-05-19 2026-09-29
trk.mail.happymammoth.co 10 2026-05-06 2026-09-01
shop.happymammoth.co 13 2026-05-16 2026-09-24
www.happymammoth.co 15 2026-05-19 2026-09-26

Programmatic access: API GET /v1/hosts/happymammoth.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/happymammoth.co.