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.

4 hosts · 211 ms

HostCertsFirst seenLast seen
image.biogen-email.com 2 2026-01-06 2026-01-21
click.biogen-email.com 1 2025-11-06 2025-11-06
pages.biogen-email.com 1 2025-11-05 2025-11-05
view.biogen-email.com 1 2025-11-06 2025-11-06

Programmatic access: API GET /v1/hosts/biogen-email.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/biogen-email.com.