usefulweb.site DNS + Certificate Explorer

Internet infrastructure explorers

DNS + Certificate Explorer

DNS records, e-mail security, CAA, live TLS certificate and CT history for a domain.

Try an example: example.com

How it works

Resolves A, AAAA, CNAME, MX, NS, TXT, CAA and SOA records, analyses e-mail spoofing protection (SPF lookups and "all" policy, DMARC policy and reporting, MTA-STS), fetches the live TLS certificate from the domain's public IP (issuer, SANs, expiry, key, chain, TLS version, browser trust) and lists recent certificates from Certificate Transparency logs via crt.sh.

  • DNS queries via the server's resolver: A, AAAA, CNAME, MX, NS, TXT, CAA, SOA for the domain and TXT at _dmarc.<domain> and _mta-sts.<domain>.
  • SPF (RFC 7208): one record allowed, max 10 DNS-querying mechanisms, policy from the "all" qualifier. DMARC (RFC 7489): p=, pct=, rua=.
  • TLS: one connection to the first public IPv4/IPv6 address on port 443 with SNI; the certificate is verified against Node's trusted root store and the hostname (private addresses are never contacted).
  • Certificate Transparency: crt.sh JSON for the exact domain, latest 25 entries (deduplicated by serial, precertificates included).

For scripts and AI agents

  • JSON API: POST https://dnscertificateexplorer.usefulweb.site/api/v1/calculate (same calculation as this page)
  • Interface description: OpenAPI 3.1 · AI guide: llms.txt
  • MCP server (Streamable HTTP): https://dnscertificateexplorer.usefulweb.site/mcp · tool name dns_certificate_explorer
Example request
curl -s -X POST https://dnscertificateexplorer.usefulweb.site/api/v1/calculate \
  -H 'content-type: application/json' \
  -d '{"domain":"example.com","certificateTransparency":false}'

Related tools

  • HeaderLens – Is a website down? Multi-region status, redirects, TLS and security headers.
  • AI Website Readiness Explorer – Can ChatGPT, Claude, Perplexity and AI agents read your website? Explainable score.
  • Explorer of Everything – Search transactions, contracts, domains, packages, advisories, MCP servers and websites in one box.
Feedback