Find every subdomain
of a domain.

Every hostname under a domain that ever appeared in a public TLS certificate — with certificate counts and first/last seen dates.

3 hosts · 293 ms

HostCertsFirst seenLast seen
tu.co.uk 2 2026-06-08 2026-06-08
cdn.tu.co.uk 1 2026-06-08 2026-06-08
www.tu.co.uk 1 2026-06-08 2026-06-08

Programmatic access: API GET /v1/hosts/tu.co.uk (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/tu.co.uk.