// about ldns
One URL,
every domain tool.
LDNS is a free, open-source toolkit for inspecting any domain on the internet: DNS records, registration data, email authentication, TLS certificates, security headers, IP geolocation, and subdomains. No accounts. No tracking. Edge-cached on Cloudflare so lookups are fast, and the whole thing is on GitHub.
// what's in the box
Six tools, one workflow.
DNS Records
A, AAAA, MX, TXT, NS, SOA, CAA and CNAME over encrypted DoH, with per-provider latency.
RDAP & WHOIS
Registration data, registrar, expiry, DNSSEC. WHOIS fallback for ccTLDs that don't support RDAP.
Email security
SPF, DMARC, DKIM, BIMI and MTA-STS, with provider detection and policy explanation.
Server response
Headers, redirect chain, TTFB, tech-stack badges, IP/ASN/country per upstream.
TLS & security
Cert from CT logs, response security headers, HSTS preload, well-known files.
Subdomains
Discovery via Certificate Transparency logs, deduplicated and exportable as CSV.
// how it's built
Edge-rendered, cache-first, no database.
DNS queries go straight to public DoH resolvers (Cloudflare, Google, DNS.SB). Server probes, TLS, ASN, subdomain and email lookups run through SvelteKit endpoints that proxy to public services and cache aggressively at the Cloudflare edge.
There is no database and no user tracking. Every lookup is a stateless GET against a cached endpoint. That's why the same lookup is essentially free at scale, and why every page is also a public API.
None of that is a claim you have to take on faith: the source for this site, the browser extension, and the shared lookup library is public. If you want to know exactly what happens to a domain you type in, you can go and read it.
// open source
Read it, fork it, improve it.
LDNS is open source under the MIT license. That covers this website, the Chrome and Firefox extension, and @ldns/core, the shared library that does the actual DNS, RDAP, email and certificate work for both.
The privacy promises above are the main reason it's public. A tool that sees every domain you look up should be one you can audit rather than trust.
Browse the source
Site, extension and shared library in one repository.
Report a bug
Something wrong or missing? Open an issue. They get read.
Contribute
Focused pull requests welcome. Start with an issue.
MIT licensed, with one exception: the LDNS name, wordmark and icons stay ours, so forks need their own branding. Everything else is yours to use.