DNS resolution · Hierarchical lookup

DNS Phonebook

Resolve a domain to an IP. The lookup chain behind every URL.

Type a URL in a browser and dozens of millisecond-scale lookups happen before the first byte arrives. The resolver walks a hierarchy: root nameservers → TLD servers (.com, .org, .io) → authoritative servers for the domain → IP address. Caching at each layer is why a repeat visit is fast.

DNS Phone Book

Type a website name to look up its address

📖 The Internet Phone Book

google.com142.250.80.46

youtube.com142.250.190.78

wikipedia.org208.80.154.224

github.com140.82.121.3

nasa.gov52.0.14.116

minecraft.net13.107.213.51

What’s happening under the hood

›DNS is a distributed key-value store keyed by domain. ~14 root servers worldwide; thousands of TLD and authoritative servers.
›Records have a TTL (time to live) — how long resolvers cache the answer. Tradeoff: faster lookups vs. slower propagation of changes (which is why DNS updates often take 'up to 48 hours').
›DNS over HTTPS (DoH) and DNS over TLS encrypt the lookup — addressing the privacy gap that plain DNS leaves wide open by default.

Dig deeper

Phase 0 · How the Internet Works

The concept you just explored is taught with full depth in the formal DURA curriculum.