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.

6 hosts · 342 ms

HostCertsFirst seenLast seenDNS
unit8.co 18 2026-05-04 2026-08-30 ok
1password.unit8.co 4 2026-05-17 2026-05-18 nxdomain
uptime.unit8.co 5 2026-05-10 2026-09-08 ok
more.unit8.co 6 2026-04-24 2026-08-20 ok
mta-sts.unit8.co 2 2026-06-09 2026-08-19 ok
www.unit8.co 16 2026-05-03 2026-08-30 ok

Programmatic access, with DNS A records: API GET /v1/hosts/unit8.co (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/unit8.co.