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.

4 hosts · 275 ms

HostCertsFirst seenLast seen
atreo.io 2 2026-02-10 2026-02-11
*.atreo.io 2 2026-02-10 2026-02-11
email.mail.atreo.io 5 2026-05-16 2026-09-13
email.atreo.io 5 2026-05-02 2026-08-30

Programmatic access: API GET /v1/hosts/atreo.io (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/atreo.io.