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 · 274 ms

HostCertsFirst seenLast seenDNS
tsukubabk-op.jp 1 2026-05-11 2026-05-11 ok
beta.tsukubabk-op.jp 18 2026-05-02 2026-10-03 ok
www.tsukubabk-op.jp 1 2026-05-11 2026-05-11 nxdomain

Programmatic access, with DNS A records: API GET /v1/hosts/tsukubabk-op.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/tsukubabk-op.jp.