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.

7 hosts · 309 ms

HostCertsFirst seenLast seenDNS
functionhealth.co 5 2026-05-02 2026-09-12 ok
*.functionhealth.co 2 2026-09-10 2026-09-12 —
links.mail.functionhealth.co 3 2026-05-04 2026-08-23 ok
links.functionhealth.co 4 2026-04-10 2026-08-19 ok
links.mail.dev.functionhealth.co 3 2026-04-30 2026-08-21 ok
links.dev.functionhealth.co 4 2026-04-30 2026-08-16 nodata
www.functionhealth.co 5 2026-05-15 2026-09-07 ok

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