What Is DNS?

How DNS Works

When you type google.com, your browser asks a DNS resolver (usually your ISP or Cloudflare 1.1.1.1) for the IP address. The resolver checks its cache, then queries root servers, TLD servers (.com), and authoritative nameservers until it finds the answer.

DNS records come in several types: A records map domains to IPv4 addresses, AAAA to IPv6, CNAME creates aliases, MX handles email routing, TXT stores verification strings, and NS delegates to nameservers.

DNS propagation — the time it takes for changes to spread across all DNS servers — can take up to 48 hours. In practice, most changes propagate within minutes to hours depending on TTL settings.

Why Developers Use DNS

Developers interact with DNS when setting up domains, configuring email, and pointing subdomains to different services. Cloudflare, Route 53 (AWS), and Google Cloud DNS are popular managed DNS providers. Understanding DNS is essential for debugging 'site not loading' issues.

Key Concepts

• A Record — Maps a domain name to an IPv4 address — the most common record type
• CNAME — Creates an alias from one domain to another — api.example.com → myapp.herokuapp.com
• TTL — Time-to-Live — how long DNS resolvers cache a record before checking for updates
• Nameserver — The authoritative server that holds the actual DNS records for a domain
• DNS Propagation — The time it takes for DNS changes to spread across the internet's DNS resolver network
• MX Record — Specifies the mail server responsible for receiving email for a domain

Common DNS Commands

# Look up A record
dig google.com A

# Look up all DNS records
dig example.com ANY

# Query specific DNS server
nslookup example.com 1.1.1.1

# Trace the full DNS resolution path
dig +trace example.com

Frequently Asked Questions