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 · 319 ms

HostCertsFirst seenLast seen
calso.tech 8 2026-05-05 2026-10-04
*.calso.tech 7 2026-05-05 2026-10-04
www.calso.tech 1 2026-09-30 2026-09-30

Programmatic access: API GET /v1/hosts/calso.tech (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/calso.tech.