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.

5 hosts · 258 ms

HostCertsFirst seenLast seenDNS
roberthalf.nl 1 2026-01-28 2026-01-28 ok
*.roberthalf.nl 1 2026-01-28 2026-01-28 —
www.m.roberthalf.nl 1 2026-01-28 2026-01-28 ok
tags.roberthalf.nl 2 2025-07-02 2026-06-02 ok
collect.roberthalf.nl 2 2025-07-02 2026-06-02 ok

Programmatic access, with DNS A records: API GET /v1/hosts/roberthalf.nl (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/roberthalf.nl.