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.

9 hosts · 263 ms

HostCertsFirst seenLast seen
rootsec.nl 29 2026-04-18 2026-09-19
*.rootsec.nl 16 2026-04-18 2026-09-19
offerte.rootsec.nl 7 2026-05-25 2026-10-07
bookstack.rootsec.nl 4 2026-06-14 2026-10-13
form.rootsec.nl 8 2026-04-23 2026-08-20
autodiscover.rootsec.nl 10 2026-06-15 2026-10-12
status.rootsec.nl 17 2026-05-29 2026-10-10
vault.rootsec.nl 3 2026-05-27 2026-08-26
www.rootsec.nl 12 2026-04-22 2026-08-19

Programmatic access: API GET /v1/hosts/rootsec.nl (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/rootsec.nl.