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.

3 hosts · 258 ms

HostCertsFirst seenLast seenDNS
gs-outboundmail.com 29 2026-05-09 2026-10-02 ok
*.gs-outboundmail.com 22 2026-05-09 2026-10-02 —
email.gsp.gs-outboundmail.com 5 2026-05-20 2026-09-16 ok

Programmatic access, with DNS A records: API GET /v1/hosts/gs-outboundmail.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/gs-outboundmail.com.