DNS & infrastructure tools

Free tools for developers and sysadmins. Look up domains, check DNS records, test email configuration and inspect SSL certificates.

Lookup

WHOIS Lookup Domain registration details, registrar, expiry dates and nameserver information. DNS Records Query any DNS record type for a domain using your local resolver. Reverse DNS Look up the hostname associated with an IPv4 or IPv6 address.

Mail

MX Checker Verify the mail exchange records and server priorities for a domain. SPF / DKIM / DMARC Check email authentication records to identify deliverability issues. Email Headers Parse raw email headers to trace the delivery path and spot delays.

Analysis

DNS Propagation Test how a DNS change has spread across multiple global resolvers. DNS Checker Compare DNS responses from Google, Cloudflare, Quad9 and Mullvad. TTL Inspector View time-to-live values on records to plan propagation windows. Zone Health Run a comprehensive health check across the key records for a domain.

Security

SSL Certificate Inspect the SSL certificate chain, expiry and subject alternative names. HTTP Headers Check which security response headers a server is returning. Blacklist Check Test whether an IP or domain appears on common email blacklists. DNS over HTTPS Query DNS records over HTTPS using the Google public DoH resolver. Reachability Test whether a domain or IP is reachable and measure its response time.