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 · 269 ms

HostCertsFirst seenLast seenDNS
realize.com 1 2025-11-27 2025-11-27 ok
*.realize.com 1 2025-11-27 2025-11-27 —
signup.realize.com 1 2025-12-02 2025-12-02 ok

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