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NIC.IO -- .IO Domain Registry
Introduced 1997
TLD type Country code top-level domain
Status Active
Registry NIC.IO (run by Internet Computer Bureau)
Sponsor IO Top Level Domain Registry (Cable and Wireless)
Intended use Entities connected with  British Indian Ocean Territory
Actual use Popular with startup companies; little of anything related to the territory itself.
Registration restrictions None for 2nd level registrations; 3rd level registrant must be resident of British Indian Ocean Territory
Structure Registrations are taken directly at the second level or at third level beneath various 2nd-level labels
Documents Terms & Conditions; Rules
Dispute policies Dispute Resolution Policy
Website NIC.IO

The Internet country code top-level domain (ccTLD) .io is assigned to the British Indian Ocean Territory.[1]

The .io domain is administered by the Internet Computer Bureau, a domain name registry company based in the United Kingdom.[2]

Google currently treats .io as a generic top-level domain (gTLD) because "users and webmasters frequently see [the domain] more generic than country-targeted".[3]


The .io domain extension has existed since 1997, and has grown steadily in popularity ever since. .io domains now compose 0.1% of all websites.[4]

The first IO-related domain to be registered was the domain data-io.com, which when it was registered in late 1986 was the 45th domain name ever to be registered.[5]

The first .io domain was not registered until 1998, when Yahoo Inc registered the domain yahoo.io.[6]


Labels for .io domains may only contain alphanumeric characters and hyphens and must be between 3 and 63 characters long. Domain names can not begin with, or end with, a hyphen symbol, and may not contain two consecutive hyphens.[7][8] The entire domain name may not contain more than 253 characters.[9]


The right to administer domain names is given to approved organisations by the IANA. The Internet Computer Bureau (ICB) administers .io domains. This domain name registry is a British company, and operates for this purpose under the name NIC.IO. The company also holds the rights to sell .sh-domains and .ac-domains, the top-level domains for the South Atlantic islands of Saint Helena and Ascension, respectively.[10]

Registration and restrictions[edit]

Both individuals and organisations are allowed to register .io-domains.

In order to register .io domains you need not be registered or established in the British Indian Ocean territory. In order to register third-level domains such as xyz.com.io you have to be an inhabitant of the area. Any second-level domains used by NIC.IO and top-level domains can not be used as a third-level domain. For example, the domain "com.com.io", "org.com.io" and "biz.com.io" are all restricted.[11]

Domain names in .io may not be used "for any purpose that is sexual or pornographic or that is against the statutory laws of any Nation". Breaching this requirement "NIC.IO reserves the right to immediately deactivate the offending registration".[11]

Dot-io domains may be registered for a minimum of one year, and a maximum of 10 years.[12]

Domain names in .io are currently priced higher than many other domains, partly due to high demand. Registering available .io-domains starts from around £30 / $32.88 US per year.[11][13][14]


The .io-domain has considerable usage unrelated to the British Indian Ocean Territory.

"Nowadays, a lot of TLDs are used without any relation to the original country, such as .ly, .io, .me."

— Jens Segers - Founder of Auki.io[15]

IO is also commonly used in IT as an abbreviation for input/output, which makes the .io domain useful for domain hacks and services wanting to be associated with technology.[16]

"We took it because it refers to ‘input-output’. And our customers (mostly tech savvy people) understand it like so."

— Ben Verbeken - Seats.io CEO[15]


The .io gTLD has become a popular alternative for startup companies.[17][18]

Online services[edit]

IO has also been taken as an abbreviation of "Internet organization".[citation needed] In addition, .io domains are often used for open source projects, APIs (such as put.io API and pen.io API) and online services.[19]


One of the main reasons behind this popularity is the availability of .io domains: Though it is often hard to find a fitting .com domain, there are plenty of corresponding .io domains available that have not yet been registered. This may be due in part to registrations being suppressed by the relatively high price of .io domain names.


According to a Gigaom interview with Paul Kane, chairman of the Internet Computer Bureau, the domain name registry is required to give some of its profits to the British government, for administration of the British Indian Ocean Territory.[15] As no indigenous Chagossians remain in the territory, the only residents being about 4,000 United States military personnel and contractors,[20] it is contended that the indigenous Chagossians do not receive any monetary benefit from the sale of the domain names.

After being questioned as a result of the interview, the British Government denied receiving any funds from the sale of .io domain names, and argued that consequentially, the profits could not be shared with the Chagossians.[21][22]


  1. ^ IDN Code Points Policy for the .IO Top Level Domain (PDF), NIC.IO 
  2. ^ "IANA — .io Domain Delegation Data". iana.org. 
  3. ^ "Geotargetable domains". Google. Retrieved 6 May 2013. 
  4. ^ "Historical trends in the usage of top level domains for websites". Retrieved 2014-10-16. 
  5. ^ "The Oldest .io domains". Retrieved 2014-10-29. 
  6. ^ "NIC.IO - The Indian Ocean .IO Domain Registry and Network Information Centre - Whois Search". Retrieved 2014-12-29. 
  7. ^ ".IO Domain". Retrieved 2014-10-29. 
  8. ^ "Eigenschaften einer .io-Domain" (in German). united-domains.de. 
  9. ^ RFC 1035, Domain names--Implementation and specification, P. Mockapetris (Nov 1987)
  10. ^ "Internet Computer Bureau". 
  11. ^ a b c "RULES for the .IO Domain and Sub-Domains". 
  12. ^ "Register dot IO (British Indian Ocean Territory) domain names". 
  13. ^ ".IO Domain at Gandi Rates". 
  14. ^ "NameCheap.com .IO domains". 
  15. ^ a b c David Meyer. "The dark side of .io: How the U.K. is making web domain profits from a shady Cold War land deal". gigaom.com. 
  16. ^ "WHY .IO?". 
  17. ^ "Popularity with startups". 
  18. ^ "IO Domains in Alexa Top 1 Million.". Retrieved 27 May 2015. 
  19. ^ Beattie, Russell (2013-02-12). "The rise of .io domains for well crafted web services". Retrieved 2014-04-24. There's lots of open source projects (Redis, Brackets, Launcher), a few mobile-app landing pages (Avocado, X-Ray), a ton of new web apps and services, several conference pages (Lightning, Renaissance, Resonate) and a few older companies or organizations who've changed their name to take advantage of a cleaner .io name. 
  20. ^ "CIA World Factbook - British Indian Ocean Territory", Central Intelligence Agency, 21 May 2014
  21. ^ "House of Lords". parliament.uk. 
  22. ^ David Meyer. "UK government denies receiving .io domain profits". gigaom.com. 

External links[edit]