Find every subdomain
of a domain.

Every hostname under a domain that ever appeared in a public TLS certificate — with certificate counts, first/last seen and live DNS status.

4 hosts · 336 ms

HostCertsFirst seenLast seenDNS
qinstruments.com 1 2026-05-04 2026-05-04 ok
osm.qinstruments.com 5 2026-06-03 2026-09-05 ok
support.qinstruments.com 8 2026-05-18 2026-09-13 ok
www.qinstruments.com 1 2026-05-04 2026-05-04 ok

Programmatic access, with DNS A records: API GET /v1/hosts/qinstruments.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/qinstruments.com.