How to Use DNS Lookup Tools to Debug Domain Issues

Published April 4, 2026 · 6 min read · By Kas

Whether you are setting up a new domain, debugging email delivery, or verifying SSL certificates, DNS lookup tools are essential in every developer's toolkit. This guide covers what DNS records are, how to query them, and which free tools to use.

What Are DNS Records?

DNS (Domain Name System) is the internet's phone book. It translates human-readable domain names into IP addresses and other routing information. Here are the key record types:

• A Records — Map a domain to an IPv4 address (e.g., 93.184.216.34)
• AAAA Records — Map a domain to an IPv6 address
• MX Records — Specify mail servers and their priority for receiving email
• NS Records — Identify the authoritative nameservers for the domain
• TXT Records — Contain text data, commonly used for SPF, DKIM, and domain verification
• CNAME Records — Create an alias from one domain name to another
• SOA Records — Contain administrative information about the zone

Common DNS Debugging Scenarios

1. Email Not Delivering

If emails to your domain are bouncing, check your MX records first. They should point to your email provider's servers with correct priority values. Lower priority numbers mean higher preference.

2. Website Not Loading After DNS Change

DNS changes can take up to 48 hours to propagate globally, but typically complete within 1-4 hours. Check your A record to verify it points to the correct IP address, and note the TTL (Time To Live) value — this tells you how long resolvers will cache the old record.

3. SSL Certificate Issues

If you are using a CDN or reverse proxy, check your CNAME records to ensure traffic is routing through the correct path. SSL certificate validation often depends on correct DNS configuration.

4. Domain Verification for Services

Many services (Google Search Console, Microsoft 365, AWS) require adding a TXT record for domain verification. Use a DNS lookup to confirm the record is live before clicking "Verify" in the service dashboard.

How DNS-over-HTTPS Works

Traditional DNS queries are sent in plaintext over UDP port 53, making them visible to anyone on the network. DNS-over-HTTPS (DoH) encrypts these queries by sending them over HTTPS, providing privacy and security.

Modern DNS lookup tools use DoH to query records directly from your browser. This means:

• No server-side processing — queries go directly from your browser to a DNS resolver like Cloudflare (1.1.1.1)
• Full privacy — the tool provider never sees your queries
• Fast results — no round-trip to a backend server

Using Our Free DNS Lookup Tool

Our DNS Lookup Tool uses Cloudflare's DNS-over-HTTPS API to query records directly from your browser. Here is how to use it:

1. Enter any domain name (no need to include https://)
2. Select which record types to query (A, AAAA, MX, NS, TXT, CNAME, SOA)
3. Click "Lookup" and see results instantly

Results show the record value and TTL (in seconds) for each record found. MX records are sorted by priority, and SOA records are broken down into individual fields.

Complementary Tools

DNS lookup is just one piece of the puzzle. For a complete diagnostic workflow, use these alongside:

• SSL Certificate Checker — Verify HTTPS certificate details and expiry dates
• HTTP Header Viewer — Inspect response headers and security header analysis
• JSON Formatter — Format and validate API responses
• Browse all 32+ developer tools

Command-Line Alternatives

For those who prefer the terminal, here are the equivalent commands:

# Query A records
dig example.com A +short

# Query MX records
dig example.com MX +short

# Query all records
dig example.com ANY

# Using nslookup
nslookup -type=TXT example.com

# Using host
host -t AAAA example.com

Browser-based tools are faster for quick checks, while CLI tools are better for scripting and automation.