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.

5 hosts · 275 ms

HostCertsFirst seenLast seen
howtogeek.com 9 2026-04-12 2026-09-14
*.howtogeek.com 19 2026-04-12 2026-09-24
sli.howtogeek.com 1 2025-12-22 2025-12-22
shop.howtogeek.com 4 2026-05-05 2026-05-19
click.newsletter.howtogeek.com 2 2026-08-17 2026-08-17

Programmatic access: API GET /v1/hosts/howtogeek.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/howtogeek.com.