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.

3 hosts · 323 ms

HostCertsFirst seenLast seenDNS
open.email.cinfin.com 3 2025-07-18 2026-07-23 ok
links.email.cinfin.com 3 2025-07-18 2026-07-23 ok
content.email.cinfin.com 3 2025-07-18 2026-07-23 ok

Programmatic access, with DNS A records: API GET /v1/hosts/email.cinfin.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/email.cinfin.com.