DNS

The DNS Hierarchy

DNS is a globally distributed, hierarchical database organized as an inverted tree. At the root is the root zone, managed by 13 root server clusters (identified as a.root-servers.net through m.root-servers.net, each anycast across hundreds of physical locations). Below the root are TLD zones (.com, .org, .net, country codes). Below TLDs are individual domain zones, each delegated to the domain owner's chosen name servers.

This hierarchy enables distributed authority: no single server knows all DNS records. Instead, each level knows how to refer queries to the next level down, until the Authoritative DNS ServerA DNS server that holds the original, definitive DNS records for a domain zone. It provides answers directly from its zone data rather than querying other servers, serving as the source of truth for that domain. server for the queried domain is reached.

Resolution Process

When you type a URL, your device checks its local cache, then queries a DNS ResolverA server that receives DNS queries from clients and resolves domain names by querying the DNS hierarchy on their behalf. Public resolvers like 1.1.1.1 (Cloudflare) and 8.8.8.8 (Google) are widely used alternatives to ISP resolvers. (usually provided by your ISP or a public resolver like 8.8.8.8 or 1.1.1.1). If the resolver does not have the answer cached, it performs recursive resolution: it queries a root server for the TLD's NS records, queries the TLD server for the domain's NS records, then queries the authoritative server for the final answer. The resolver caches results according to TTL values and returns the answer to your device.

DNS Record Types

DNS stores different types of information as different record types. A RecordA DNS record that maps a domain name to an IPv4 address (e.g., example.com -> 93.184.216.34). The most fundamental DNS record type for resolving domain names to IP addresses. maps names to IPv4Internet Protocol version 4. The fourth revision of IP using 32-bit addresses (e.g., 192.168.1.1), providing approximately 4.3 billion unique addresses. Still the most widely used internet protocol despite address exhaustion. addresses. AAAA RecordA DNS record that maps a domain name to an IPv6 address. Named "AAAA" (quad-A) because an IPv6 address is four times the size of an IPv4 address. maps to IPv6Internet Protocol version 6. The successor to IPv4 using 128-bit addresses (e.g., 2001:0db8::1), providing a virtually unlimited address space of 3.4 x 10^38 addresses. Designed to solve IPv4 address exhaustion.. CNAME RecordA DNS record that creates an alias from one domain name to another (e.g., www.example.com -> example.com). The alias inherits all DNS records of the target, but cannot coexist with other record types at the same name. creates aliases. MX RecordMail Exchange record. A DNS record that specifies the mail server responsible for receiving email for a domain, along with a priority value that determines the order in which servers are tried. routes email. NS RecordName Server record. A DNS record that delegates a domain or subdomain to a set of authoritative DNS servers. Every domain must have at least two NS records for redundancy. delegates zones. PTR RecordPointer record. A DNS record used for reverse DNS lookups, mapping an IP address back to a domain name. Essential for email server verification and network diagnostics. enables reverse lookups. TXT records store arbitrary text used for domain verification, SPF, DKIM, and DMARC policies.

DNS is unencrypted by default — responses can be observed by network intermediaries. DNS over HTTPS (DoH) and DNS over TLS (DoT) encrypt queries to prevent surveillance and manipulation. Use DNS Lookup to query any record type, and DNS Leak Test to verify your resolver is not leaking queries unexpectedly.