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.

5 hosts · 299 ms

HostCertsFirst seenLast seenDNS
simera.com 3 2026-06-08 2026-08-16 ok
en.simera.com 3 2026-06-09 2026-08-17 ok
ar.simera.com 3 2026-06-07 2026-08-15 ok
mta-sts.simera.com 3 2026-06-29 2026-09-23 ok
www.simera.com 3 2026-06-08 2026-08-16 ok

Programmatic access, with DNS A records: API GET /v1/hosts/simera.com (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/simera.com.