Find every subdomain
of a domain.

Every hostname under a domain that ever appeared in a public TLS certificate — with certificate counts, first/last seen and live DNS status.

4 hosts · 272 ms

HostCertsFirst seenLast seenDNS
a2dda.org 5 2026-05-20 2026-09-19 ok
devsite.a2dda.org 5 2026-05-20 2026-09-19 ok
mta-sts.a2dda.org 5 2026-05-15 2026-09-15 ok
www.a2dda.org 5 2026-05-20 2026-09-19 ok

Programmatic access, with DNS A records: API GET /v1/hosts/a2dda.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/a2dda.org.