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.

22 hosts · 269 ms

HostCertsFirst seenLast seen
vpnpd.rtresolutions.com 4 2025-08-29 2026-08-30
conf.rtresolutions.com 1 2026-02-24 2026-02-24
api.rtresolutions.com 4 2026-04-29 2026-09-29
vpnjm.rtresolutions.com 4 2025-08-29 2026-08-30
dialin.rtresolutions.com 1 2026-02-24 2026-02-24
vpn.rtresolutions.com 5 2025-08-29 2026-08-30
www.vpn.rtresolutions.com 4 2025-08-29 2026-08-30
sip.rtresolutions.com 1 2026-02-24 2026-02-24
www.sip.rtresolutions.com 1 2026-02-24 2026-02-24
ftp.rtresolutions.com 2 2025-12-28 2026-05-14
www.ftp.rtresolutions.com 1 2025-12-28 2025-12-28
vpnhq.rtresolutions.com 4 2025-08-29 2026-08-30
vpndr.rtresolutions.com 5 2025-08-29 2026-08-30
lyncdiscover.rtresolutions.com 1 2026-02-24 2026-02-24
docs.rtresolutions.com 4 2026-04-29 2026-09-29
calyxpds.rtresolutions.com 4 2025-08-29 2026-08-12
www.calyxpds.rtresolutions.com 4 2025-08-29 2026-08-12
meet.rtresolutions.com 1 2026-02-24 2026-02-24
s4bwebext.rtresolutions.com 1 2026-02-24 2026-02-24
av.rtresolutions.com 1 2026-02-24 2026-02-24
dev.rtresolutions.com 3 2026-05-01 2026-10-01
vpnaz.rtresolutions.com 4 2025-08-29 2026-08-30

Programmatic access: API GET /v1/hosts/rtresolutions.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/rtresolutions.com.