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.

13 hosts · 237 ms

HostCertsFirst seenLast seen
opten.hu 2 2026-01-08 2026-01-08
*.opten.hu 2 2026-01-08 2026-01-08
elearning.opten.hu 10 2026-05-17 2026-09-16
hirlevel.opten.hu 5 2026-04-28 2026-08-27
hetihirlevel.opten.hu 5 2026-04-28 2026-08-27
edm.opten.hu 5 2026-04-28 2026-08-27
admin.opten.hu 5 2026-04-28 2026-08-27
mnbfelmeres.opten.hu 5 2026-04-29 2026-08-28
elemzes.opten.hu 5 2026-04-29 2026-08-27
ajanlat.opten.hu 5 2026-04-28 2026-08-27
percona.int.opten.hu 1 2026-10-06 2026-10-06
argocd.int.opten.hu 1 2026-10-06 2026-10-06
rendezveny.opten.hu 5 2026-04-28 2026-08-27

Programmatic access: API GET /v1/hosts/opten.hu (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/opten.hu.