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.

9 hosts · 299 ms

HostCertsFirst seenLast seen
unit21.ai 13 2026-05-29 2026-09-24
track.unit21.ai 12 2026-06-10 2026-10-07
sl.unit21.ai 5 2026-05-25 2026-09-22
go.unit21.ai 8 2026-04-19 2026-08-15
docs.unit21.ai 14 2026-05-29 2026-09-24
legacy.docs.unit21.ai 5 2026-04-24 2026-08-22
support.unit21.ai 7 2026-03-24 2026-08-30
trust.unit21.ai 11 2026-05-29 2026-09-24
www.unit21.ai 6 2026-05-05 2026-08-31

Programmatic access: API GET /v1/hosts/unit21.ai (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/unit21.ai.