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 · 279 ms

HostCertsFirst seenLast seenDNS
kakuyomu.jp 2 2025-07-06 2026-06-06 ok
cdn-static.kakuyomu.jp 2 2025-07-06 2026-06-06 ok
sendgrid.kakuyomu.jp 1 2026-01-23 2026-01-23 ok
admin.kakuyomu.jp 2 2025-08-08 2026-07-08 ok

Programmatic access, with DNS A records: API GET /v1/hosts/kakuyomu.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/kakuyomu.jp.