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.

7 hosts · 290 ms

HostCertsFirst seenLast seenDNS
helo.ai 1 2026-04-20 2026-04-20 ok
*.helo.ai 1 2026-04-20 2026-04-20 —
voicebeta.helo.ai 1 2026-09-07 2026-09-07 nodata
www.voicebeta.helo.ai 1 2026-09-07 2026-09-07 nxdomain
voiceapp.helo.ai 1 2026-04-02 2026-04-02 ok
www.voiceapp.helo.ai 1 2026-04-02 2026-04-02 nxdomain
docs.helo.ai 42 2026-04-14 2026-09-20 ok

Programmatic access, with DNS A records: API GET /v1/hosts/helo.ai (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/helo.ai.