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
assuredly.co 6 2026-04-14 2026-08-11 ok
hello.assuredly.co 13 2026-05-31 2026-09-26 ok
app.assuredly.co 4 2026-05-18 2026-09-09 ok
www.assuredly.co 10 2026-04-15 2026-08-12 ok

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