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 · 323 ms

HostCertsFirst seenLast seenDNS
j2mssp.com 12 2026-05-06 2026-09-12 ok
*.j2mssp.com 7 2026-05-17 2026-09-12 —
mta-sts.j2mssp.com 4 2026-05-04 2026-07-28 ok
www.j2mssp.com 5 2026-05-06 2026-09-11 ok

Programmatic access, with DNS A records: API GET /v1/hosts/j2mssp.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/j2mssp.com.