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.

2 hosts · 236 ms

HostCertsFirst seenLast seen
nextmatter.co 2 2026-03-08 2026-07-24
www.nextmatter.co 2 2026-03-08 2026-07-24

Programmatic access: API GET /v1/hosts/nextmatter.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/nextmatter.co.