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.

5 hosts · 194 ms

HostCertsFirst seenLast seen
sojern.org 10 2026-05-11 2026-09-06
cl.sojern.org 3 2026-05-30 2026-08-29
opn.sojern.org 5 2026-05-30 2026-08-29
opt.sojern.org 3 2026-05-30 2026-08-29
www.sojern.org 8 2026-05-04 2026-08-30

Programmatic access: API GET /v1/hosts/sojern.org (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/sojern.org.