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.

2 hosts · 242 ms

HostCertsFirst seenLast seenDNS
img.info3.supersmart.com 14 2026-04-28 2026-08-24 nxdomain
r.info3.supersmart.com 3 2026-06-15 2026-09-03 ok

Programmatic access, with DNS A records: API GET /v1/hosts/info3.supersmart.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/info3.supersmart.com.