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.

6 hosts · 191 ms

HostCertsFirst seenLast seen
v3.co 6 2026-04-03 2026-08-24
trail.v3.co 4 2026-06-10 2026-10-07
spin.v3.co 4 2026-05-03 2026-10-10
api.spin.v3.co 3 2026-05-20 2026-09-03
app.v3.co 5 2026-04-16 2026-08-13
www.v3.co 6 2026-04-03 2026-08-24

Programmatic access: API GET /v1/hosts/v3.co (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/v3.co.