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.

6 hosts · 267 ms

HostCertsFirst seenLast seen
coolworks.com 22 2025-12-20 2026-10-07
*.coolworks.com 21 2025-07-11 2026-10-07
help.coolworks.com 7 2026-04-30 2026-09-24
employerhelp.coolworks.com 7 2026-04-30 2026-09-24
test.coolworks.com 11 2026-05-09 2026-09-05
www.coolworks.com 2 2025-12-20 2026-09-27

Programmatic access: API GET /v1/hosts/coolworks.com (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/coolworks.com.