DNS translates domain names into IP addresses—the phone book of the Internet. Every website, email, and app depends on this invisible lookup happening in milliseconds.
DNS servers answer two questions: what's the IP address, and who's allowed to tell you? The second question is the interesting one—it involves a hierarchy of trust, thousands of organizations, and infrastructure designed to survive its own failures.
Your device doesn't resolve DNS—it asks someone else to do it. That someone sees every domain you visit. Understanding resolvers means understanding who's watching.
Your browser needs an IP address but only has a name. DNS resolution is how one becomes the other—a journey through caches, resolvers, and a hierarchy that narrows four billion possibilities down to one.
DNS is a hierarchy where no one knows everything, but everyone knows who to ask next. Root servers point to TLD servers, TLD servers point to authoritative nameservers—each level knowing just enough to hand off the question.
Your computer asks one question and gets one answer. Behind that simplicity, your DNS resolver is following referrals across the hierarchy, asking servers that only say 'not my job—ask them instead.' This division of labor is why DNS can serve the entire Internet.
DNS caching is a bet that the world hasn't changed since you last asked. Here's how that bet plays out across four layers of memory, and what happens when it's wrong.
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