About DNS Lookup

DNS resolution and record lookup. Part of the DevTools Surf developer suite. Browse more tools in the Networking collection.

Use Cases

• Verify DNS propagation after changing A records for a domain migration
• Debug email delivery issues by checking MX and SPF/DKIM TXT records
• Identify which nameservers are authoritative for a domain
• Diagnose CDN configuration by checking CNAME chains

Tips

• Query specific record types using the selector: A (IPv4), AAAA (IPv6), MX (mail), TXT (SPF, DKIM), CNAME, NS, and SOA — 'all' is useful for a complete audit
• Compare results from multiple resolvers (Google 8.8.8.8, Cloudflare 1.1.1.1, your ISP) to diagnose DNS propagation delays or resolver-specific issues
• The TTL field in results tells you how long resolvers will cache the record — a low TTL (60-300s) is appropriate before a DNS change; restore to normal (3600-86400s) afterward

Fun Facts

• DNS (Domain Name System) was invented by Paul Mockapetris in 1983. Before DNS, host-to-IP mappings were maintained in a single HOSTS.TXT file distributed via FTP — by 1982 the file had grown too large for manual maintenance.
• There are 13 root DNS server clusters worldwide (labeled A through M), but each cluster uses anycast routing to hundreds of physical servers. The total number of root server instances globally exceeds 1,800 — making DNS one of the most distributed systems in computing.
• DNS over HTTPS (DoH) was standardized in RFC 8484 (2018) and encrypts DNS queries to prevent ISP interception and eavesdropping. Browser-based DoH (Mozilla, Chrome) bypasses the OS resolver entirely — a change that fragmented traditional enterprise DNS filtering.

FAQ

Why do different DNS resolvers return different results?

DNS changes propagate gradually — each resolver's cache reflects when it last looked up the record. High TTL records take longer to propagate. Use multiple resolvers to check propagation status; when all return the new value, propagation is complete.

What is the difference between A and CNAME records?

An A record maps a hostname directly to an IP address. A CNAME maps a hostname to another hostname (an alias). When a browser resolves a CNAME, it follows the chain until it finds an A record. Root domains (example.com without www) cannot use CNAME records.

What are DNS TXT records used for?

TXT records hold arbitrary text data, most commonly: SPF (sender policy framework for email anti-spoofing), DKIM keys (email signing), DMARC policies, domain ownership verification (Google Search Console, SSL issuers), and various SaaS service verification.