# nstool.app

> Free DNS lookup and diagnostics tool. Live DNS data for any domain: records, authoritative nameservers, resolver propagation and e-mail authentication (SPF, DKIM, DMARC). Every URL returns plain text when fetched without "Accept: text/html", so it is easy to use from scripts and AI agents.

## URLs (plain text unless the client asks for HTML)

- https://nstool.app/{domain} — common records (A, AAAA, CNAME, MX, NS, TXT, SOA, CAA, HTTPS, DS)
- https://nstool.app/{domain}/{type} — one record type, e.g. https://nstool.app/example.com/mx
- https://nstool.app/{ip} — reverse DNS (PTR)
- https://nstool.app/auth/{domain}[/{type}] — query every authoritative nameserver: SOA serials, delegation, lame delegation, DNSSEC
- https://nstool.app/resolvers/{domain}[/{type}] — compare answers of 8 public resolvers (propagation)
- https://nstool.app/mail/{domain} — MX + reverse DNS, SPF (with lookup count), DMARC, DKIM, MTA-STS, TLS-RPT, BIMI
- Optional query parameter on lookups: ?server=cloudflare|google|quad9|opendns|adguard|controld|dnssb|yandex or a public IP

## JSON API

- https://nstool.app/api/lookup?name={domain}&type={type|ALL}&server={id|ip}&dnssec=1
- https://nstool.app/api/auth?name={domain}&type={type}
- https://nstool.app/api/resolvers?name={domain}&type={type}
- https://nstool.app/api/mail?domain={domain}&selectors={dkim selectors, comma separated}
- https://nstool.app/api/servers — available resolvers and record types

Results are live (not cached) and rate-limited per client IP.