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 · 220 ms

HostCertsFirst seenLast seenDNS
rms.ne.jp 2 2025-12-02 2025-12-03 ok
mail.rms.ne.jp 5 2026-05-17 2026-08-14 ok
webmail.rms.ne.jp 3 2026-06-15 2026-08-14 ok
www.rms.ne.jp 2 2025-12-02 2025-12-03 ok

Programmatic access, with DNS A records: API GET /v1/hosts/rms.ne.jp (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/rms.ne.jp.