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 · 252 ms

HostCertsFirst seenLast seenDNS
biggastone.com 2 2026-05-05 2026-05-06 ok
img.mail.biggastone.com 12 2026-05-07 2026-09-02 ok
r.mail.biggastone.com 3 2026-06-16 2026-09-04 ok
www.biggastone.com 2 2026-05-05 2026-05-06 ok

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