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 · 187 ms

HostCertsFirst seenLast seen
mail.genentech.com 4 2026-07-03 2026-07-03
m.mail.genentech.com 3 2025-06-19 2026-05-27
res.mail.genentech.com 3 2025-06-19 2026-05-27
t.mail.genentech.com 3 2025-06-19 2026-05-27

Programmatic access: API GET /v1/hosts/mail.genentech.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/mail.genentech.com.