DNS root servers are the authoritative name servers for the DNS root zone, the top of the public Domain Name System. In an uncached lookup, they do not normally hand over a website’s final IP address. They tell a recursive resolver which top-level domain, or TLD, name servers to ask next, starting the route toward the domain’s own authoritative server.
The setup is often described badly as “the internet has 13 root servers.” It has 13 named root authorities, A through M, in the root zone. Each authority is backed by a changing fleet of redundant server instances in many locations. A count without saying which of those two things it means is not much of a count.
How DNS root servers handle a lookup
DNS is a distributed, tree-shaped database: different authoritative name servers hold answers for different parts of the naming tree. A recursive resolver is the DNS service doing the legwork on behalf of a browser, device or local network.
- The resolver checks its cache. If it already has a usable answer for www.example.com, it can return it without contacting the root.
- The resolver asks a root authority. If it needs to start from scratch, it asks one of the root-server networks about .com. The root response is a referral: the names and addresses of the authoritative servers for that TLD.
- The resolver asks the TLD server. The .com server refers it onward to the authoritative name servers for example.com.
- The resolver asks the domain’s authoritative server. That server returns the requested DNS record, such as the IP address for www.example.com. The resolver can cache the result and send it back to the client.
The root’s job is closer to directing a resolver to the correct aisle than stocking every item in the building. The root zone provides its own records and delegations; individual domains publish their own answers.
Why 13 names do not mean 13 machines
The root zone configures 13 named authorities, a.root-servers.net through m.root-servers.net. That is the stable, logical layer a resolver queries. The organizations behind those names run many instances across countries and networks.
The root server system uses anycast to distribute multiple instances globally. Asking for one root letter therefore does not identify one particular physical machine.
The Root Server Technical Operations Association reported 2,003 operational instances on August 14, 2026. That is an operational snapshot, not a permanent total. IANA describes the system more durably as hundreds of servers in many countries. The enduring number is 13 authorities; the instance total needs a date.
Who runs the A through M root authorities
Twelve independent organizations operate the 13 names. Verisign operates two, A and J. IANA publishes the current addresses and operator details; addresses are configuration data, not something to hard-code into a permanent explainer.
- A: Verisign, Inc.
- B: University of Southern California, Information Sciences Institute
- C: Cogent Communications
- D: University of Maryland
- E: NASA, Ames Research Center
- F: Internet Systems Consortium, Inc.
- G: US Department of Defense, NIC
- H: US Army Research Lab
- I: Netnod
- J: Verisign, Inc.
- K: RIPE NCC
- L: ICANN
- M: WIDE Project
How a resolver finds the root in the first place
A resolver cannot use DNS to discover root addresses before it knows how to reach DNS’s starting point. The bootstrap is a root hints file, a list of root-server hostnames and IP addresses. Resolver operators typically configure it, and many resolver packages ship with a built-in list.
That file is a starting map, not a replacement for DNS. Once a resolver reaches a root authority, it receives referrals from the live DNS hierarchy and continues the lookup from there. IANA publishes root-hints and address information.
What root servers do, and what they do not do
- They do: serve the root zone and provide authoritative referrals for TLDs such as .com, .org and country-code domains.
- They do: provide a common starting layer for recursive resolution when a resolver lacks a cached route.
- They do not normally: store the final address for every website.
- They do not: make the 13 named authorities equal to 13 physical machines.
The root system is a shared, tightly scoped directory service at the top of public DNS, operated by multiple organizations and delivered through a much larger network than its A-to-M naming scheme suggests.
Frequently asked questions
Why are there 13 DNS root server names but thousands of root-server instances?
The DNS root zone lists 13 named authorities, A through M. Each named authority is delivered by multiple instances in different locations, so the number of operational instances is much larger and changes over time. The Root Server Technical Operations Association reported 2,003 operational instances on August 14, 2026.
What is a root hints file?
A root hints file contains the names and IP addresses of DNS root servers. A recursive resolver uses it to bootstrap resolution because it needs an initial way to contact the DNS root before DNS can direct it elsewhere. Many resolver software packages include such a list.
What happens after a DNS resolver receives a referral from a root server?
The resolver queries the referred TLD name server, such as the servers responsible for .com. That server refers it to the authoritative name servers for the specific domain, and the resolver then asks those servers for the requested DNS record.
Sources
- Root Servers — www.iana.org
- Root name server — en.wikipedia.org
- Root Server Technical Operations Association — root-servers.org
- Study of Deployment and Service Level of DNS Root in India — dl.acm.org
