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 · 237 ms

HostCertsFirst seenLast seenDNS
booklooker.de 1 2026-03-05 2026-03-05 ok
*.booklooker.de 1 2026-03-05 2026-03-05 —
nagios.booklooker.de 5 2026-05-04 2026-09-02 ok

Programmatic access, with DNS A records: API GET /v1/hosts/booklooker.de (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/booklooker.de.