Humans can’t remember IP addresses (142.250.183.46), but computers need them. Without DNS, we’d have to memorize strings of numbers for every website—a completely unusable internet.
DNS is the phonebook of the internet. It translates human-readable domain names (google.com) into machine-readable IP addresses. When you type a URL, DNS servers look up the corresponding IP and direct your request there.
- Query: Your browser asks a DNS resolver: “What’s the IP for google.com?”
- Resolution: The resolver checks its cache; if not found, it queries root servers, then TLD servers (.com), then authoritative nameservers
- Response: The resolver returns the IP address (e.g., 142.250.183.46)
- Connection: Your browser now connects to that IP address
This happens in milliseconds. DNS uses caching heavily—once resolved, subsequent requests don’t need to go through the full lookup.
- Hierarchical distributed database
- Caches results to speed up repeated lookups
- Multiple record types: A (IPv4), AAAA (IPv6), CNAME (alias), MX (mail), TXT
- Operates on UDP port 53 (typically)
- Anycast allows multiple servers to serve the same domain from different locations
- Built from: IP Address — DNS resolves to IP addresses
- Builds into: HTTP — HTTP requests need an IP, which DNS provides
- Builds into: DNS Lookup — DNS lookup is the full resolution process
- Related: Port — IP + port identifies the final destination
- Related: DNS Cache — caching speeds up DNS resolution
- Related: Recursive DNS — does the heavy lifting for clients
- Contrasts with: Circuit Switching — DNS is packet-based, not circuit-based
- DNS poisoning/caching attacks can redirect users to malicious sites
- DNS can be slow for first-time lookups—that’s why browsers cache aggressively
- Changing DNS records can take time to propagate (TTL)
- Some networks block certain DNS queries