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.

12 hosts · 231 ms

HostCertsFirst seenLast seen
headmasters.com 17 2026-05-01 2026-10-02
*.headmasters.com 17 2026-05-01 2026-10-02
mail1.headmasters.com 5 2026-06-24 2026-06-25
vpn1.headmasters.com 5 2026-06-24 2026-06-25
employee.headmasters.com 5 2026-05-03 2026-09-02
customercare.headmasters.com 5 2026-05-12 2026-09-09
mta-sts.corporate.headmasters.com 2 2026-04-02 2026-09-02
mail.headmasters.com 5 2026-06-24 2026-06-25
vpn.headmasters.com 5 2026-06-24 2026-06-25
gcp.headmasters.com 3 2026-05-21 2026-09-07
mta-sts.headmasters.com 1 2026-05-10 2026-05-10
property.headmasters.com 5 2026-05-12 2026-09-09

Programmatic access: API GET /v1/hosts/headmasters.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/headmasters.com.