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 · 247 ms

HostCertsFirst seenLast seen
sophos.de 1 2026-01-24 2026-01-24
secure.sophos.de 1 2026-02-18 2026-02-18
mta-sts.sophos.de 7 2026-06-03 2026-10-01
www.sophos.de 2 2026-03-18 2026-08-18

Programmatic access: API GET /v1/hosts/sophos.de (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/sophos.de.