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 · 251 ms

HostCertsFirst seenLast seen
websec.nl 10 2026-02-25 2026-07-18
*.websec.nl 19 2026-04-16 2026-10-10
clerk.websec.nl 2 2026-04-21 2026-04-21
www.websec.nl 3 2026-02-25 2026-03-02

Programmatic access: API GET /v1/hosts/websec.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/websec.nl.