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 · 248 ms

HostCertsFirst seenLast seenDNS
r-ac.co.jp 1 2026-05-13 2026-05-13 nodata
*.r-ac.co.jp 1 2026-05-13 2026-05-13 —
form.r-ac.co.jp 8 2026-04-23 2026-08-20 ok

Programmatic access, with DNS A records: API GET /v1/hosts/r-ac.co.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/r-ac.co.jp.