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 · 233 ms

HostCertsFirst seenLast seen
cloud.happlans.org 2 2025-06-18 2026-06-05
image.happlans.org 3 2026-01-21 2026-09-07
click.happlans.org 2 2025-06-18 2026-06-05
view.happlans.org 2 2025-06-18 2026-06-05

Programmatic access: API GET /v1/hosts/happlans.org (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/happlans.org.