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 · 218 ms

HostCertsFirst seenLast seen
cloud.communication.riuclass.com 2 2026-01-25 2026-01-26
image.communication.riuclass.com 2 2026-01-06 2026-02-16
click.communication.riuclass.com 1 2026-01-25 2026-01-25
view.communication.riuclass.com 1 2026-01-25 2026-01-25

Programmatic access: API GET /v1/hosts/communication.riuclass.com (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/communication.riuclass.com.