Limits RegistryPUBLIC RECORD
Limits RegistryThere are exactly 13 named DNS root servers, operated by 12 different organizations including Verisign, ICANN, and the U.S. Department of Defense, a count that has been fixed since the 1990s. Although the number of named root servers is capped at 13, each is anycast across hundreds of physical server instances worldwide today, so the original historical constraint (fitting root server addresses into one 512-byte UDP DNS response) no longer limits real-world root-server capacity or resilience the way it once did.
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There are exactly 13 named DNS root servers, operated by 12 different organizations including Verisign, ICANN, and the U.S. Department of Defense, a count that has been fixed since the 1990s. Although the number of named root servers is capped at 13, each is anycast across hundreds of physical server instances worldwide today, so the original historical constraint (fitting root server addresses into one 512-byte UDP DNS response) no longer limits real-world root-server capacity or resilience the way it once did.
The Domain Name System's root zone is served by exactly 13 named root server addresses (a.root-servers.net through m.root-servers.net), a count fixed since the 1990s by the original 512-byte UDP DNS message size limit that constrained how many server addresses could fit in a single response.
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Permanent ID limitsregistry.com/limits/LR-DNS-ROOT-SERVER-COUNT
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Limits Registry. LR-DNS-ROOT-SERVER-COUNT. Fixed number of DNS root server names in the domain name system. 2026.