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.

9 hosts · 339 ms

HostCertsFirst seenLast seenDNS
potomactech.net 23 2026-04-17 2026-09-22 ok
*.potomactech.net 16 2026-04-17 2026-09-22 —
r2.potomactech.net 2 2026-08-12 2026-08-12 ok
secure.potomactech.net 5 2026-05-21 2026-09-17 ok
contracts.potomactech.net 2 2026-09-10 2026-09-10 ok
*.contracts.potomactech.net 2 2026-09-10 2026-09-10 —
mta-sts.potomactech.net 10 2026-04-20 2026-10-02 ok
www.potomactech.net 5 2026-05-20 2026-08-21 ok
*.www.potomactech.net 2 2026-08-21 2026-08-21 —

Programmatic access, with DNS A records: API GET /v1/hosts/potomactech.net (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/potomactech.net.