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.

2 hosts · 255 ms

HostCertsFirst seenLast seen
img.news.busy.app 6 2026-05-22 2026-09-17
r.news.busy.app 4 2026-04-20 2026-09-27

Programmatic access: API GET /v1/hosts/news.busy.app (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/news.busy.app.