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.

10 hosts · 169 ms

HostCertsFirst seenLast seenDNS
mail.studentaid.gov 4 2025-09-10 2026-09-23 nodata
*.mail.studentaid.gov 4 2026-03-16 2026-09-15 —
track.mail.studentaid.gov 8 2025-09-10 2026-09-25 ok
rttrack.mail.studentaid.gov 8 2025-09-10 2026-09-25 ok
mirror.mail.studentaid.gov 8 2025-09-10 2026-09-25 ok
rtmirror.mail.studentaid.gov 8 2025-09-10 2026-09-25 ok
res.mail.studentaid.gov 8 2025-09-10 2026-09-25 ok
rtres.mail.studentaid.gov 8 2025-09-10 2026-09-25 ok
notify.mail.studentaid.gov 8 2025-09-10 2026-09-25 ok
rtnotify.mail.studentaid.gov 8 2025-09-10 2026-09-25 ok

Programmatic access, with DNS A records: API GET /v1/hosts/mail.studentaid.gov (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/mail.studentaid.gov.