us is theInternetcountry code top-level domain (ccTLD) for theUnited States. It was established in February 1985. Registrants of us domains must be U.S. citizens, residents, or organizations – or foreign entities with a presence in the United States or a territory of the United States.[2] Most registrants in the U.S. have registered for.com,.net,.org and othergTLDs, instead ofus, which has primarily been used by state and local governments, even though private entities may also registerus domains.[3] The domain is managed byRegistry Services, LLC, an acquired subsidiary domain name registry ofGoDaddy, on behalf of theUnited States Department of Commerce.[4]
Domainus is less commonly used by American businesses and enterprises than the internationally more commoncom.[5]
Postel and his colleague Ann Westine Cooper[8] codified theus ccTLD's policies in December 1992 as RFC 1386[9] and revised them the following June in RFC 1480. Registrants could only register third-level domains or higher in a geographic and organizational hierarchy. From June 1993 to June 1997, Postel delegated the vast majority of the geographic subdomains underus to various public and private entities.us registrants could register with the delegated manager for the specific zone they wished to register in, but not directly with theus administrator. In July 1997, Postel instituted a "50/500 rule" that limited each delegated manager to 500 localities maximum, 50 in a given state.[10]
In June 1998, Postel raised the possibility of coveringIANA operating costs by charging locality name registrars, who would pass the costs along to individual registrants. In September 1998, theUnited States Postal Service proposed funding the operations in order to assume control ofus, as part of a plan to diversify away from postage revenue.[11] On October 1, 1998, the NSF transferred oversight of theus domain to theNational Telecommunications and Information Administration (NTIA) of theUnited States Department of Commerce.[12] Postel died that month, leaving his domain administration responsibilities with ISI. In December 2000, these responsibilities were transferred to Network Solutions, which had recently been acquired byVerisign.[10][13][14]
On October 26, 2001,Neustar was awarded the contract to administerus. On April 24, 2002, second-level domains underus became available for registration. One of the firstusdomain hacks, icio.us, was registered on May 3, 2002, for the creation of the subdomaindel.icio.us.[15][16] A moratorium was placed on additional delegations of locality-based namespaces, and Neustar became the default delegate for undelegated localities.[17] Neustar's contract was renewed by theNational Telecommunications and Information Administration (NTIA) in 2007 and most recently in 2014.[10][18]
On March 31, 2019, theus registry made it clear that under its Acceptable Use Policy it would not allow the sale of opioids through theus top level domain.[19]
In Q2 2020,GoDaddy acquired Neustar's registry business.[20]
Theus ccTLD is historically organized under a complexlocality namespace hierarchy. Until second-level registrations were introduced in 2002,us permitted only fourth-level domain registrations of the formorganization-name.locality.state.us, with some exceptions for government entities. Registrants of locality-based domains must meet the same criteria as in the rest of theus ccTLD. Though the locality namespace is most commonly used for government entities, it is also open to registrations by private businesses and individuals. Since 2002, second-level domain registrations have eclipsed those in the locality namespace, and many local governments have transitioned to.org and other TLDs.[10] In the 2010s, the firsttop-level domains for U.S. cities became available as paid alternatives to third-level locality domains, including.nyc as an alternative to .new-york.ny.us.
Many locality-based zones ofus are delegated to various public and private entities known asdelegated managers. Domains in these zones are registered through the delegated manager, rather than through GoDaddy. As the delegated managers are expected to receive requests directly from registrants, few if anydomain name registrars serve this space, possibly contributing to its lower visibility and utilization. RFC 1480 describes the rationale for the locality namespace's deep hierarchy and local delegation:[10]
One concern is that things will continue to grow dramatically, and this will require more subdivision of the domain name management. Maybe the plan for the US Domain is overkill on growth planning, but there has never been overplanning for growth yet.
This hierarchical system has proven unappealing to companies that operate nationally or globally.[21]
As of October 31, 2013, 12,979 domains were registered under the locality namespace, of which 3,653 were managed by about 1,300 delegated managers while 9,326 were managed by Neustar as thede facto manager.[22] According to a 2013 survey of 539 delegated managers, 282 were state or local government agencies, while 98 were private individuals and 85 were commercialInternet service providers. Nearly 90% of the respondents offer domain registrations for free.[10]
The.au and.ca ccTLDs have also established third- and fourth-level locality namespaces, though the .ca locality namespace is no longer open to registrations. The.cn ccTLD maintains a third-level locality namespace in general use.
A state's main government portal is usually found at the third-level domain state.state.us, which is reserved for this purpose. However, some state administrations prefer.gov domains: for example,California's government portal is located atwww.ca.gov. Other than for state governments, no third-level domain registrations are permitted under state or territory second-level domains.
A few additional names are reserved at the second level for government agencies that are not subordinate to a state government:
A large number of third-level domains are reserved for localities within states. Each fourth-level domain registration under this namespace follows the formatorganization-name.locality.state.us, wherestate is a state's two-letter postal abbreviation andlocality is a hyphenated name that corresponds to aZIP code or appears in a well-known atlas.[10] Some delegated managers alternatively register domains under common abbreviations of locality names, such as:
In some cases, a local government that serves as the delegated manager for its own locality may locate its website directly under thelocality, omitting theorganization-name. For example, the website of the City ofBrunswick, Ohio, is located atwww.brunswick.oh.us rather than www.ci.brunswick.oh.us, and the website ofDelhi Township, Ohio, is located atwww.delhi.oh.us instead of www.twp.delhi.oh.us. Unusually,Lima, Ohio, is located atwww.cityhall.lima.oh.us.
k12: public elementary and/or secondary unified school districts (district-name.k12.state.us) individual schools (school-name.k12.state.us). Also used by public agencies overseeing educational institutions.
Some of these affinity namespaces have been supplanted by more convenientsponsored top-level domains. The first sTLD,.museum, became available in October 2001 as an alternative to the .mus namespace. Since April 2003, the.edu top-level domain has been available as an alternative for community colleges, technical and vocational schools, and other tertiary educational institutions that might have previously used the .cc or .tec affinity namespaces.[26]
The Dot Kids Implementation and Efficiency Act of 2002 (Pub. L.107–317 (text)(PDF)) established a.kids.ussecond-level domain. The general public could register third-level domains under.kids.us for educational content that met strict requirements, including conformance to theChildren's Online Privacy Protection Act and adherence toChildren's Advertising Review Unit standards. Webpages were prohibited from linking outside the.kids.us namespace. On July 27, 2012, in response to declining usage and a petition by Neustar the previous year, the NTIA suspended.kids.us registrations. By that time, 651 domains were registered under.kids.us, and only five registrants (Nickelodeon,Nick Jr.,PBS Kids, theSmithsonian Center for Education and Museum Studies, and Super-Fun Sports Inc., operating trampoline.kids.us and trampolines.kids.us) were operating active websites.[27]
Underus nexus requirements,us domains may be registered only by the following qualified entities:
Any United States citizen or resident,
Any United States entity, such as organizations or corporations,
Any foreign entity or organization with abona fide presence in the United States
To ensure that these requirements are met,GoDaddy frequently conducts "spot checks" on registrant information.
To prevent anonymous registrations that do not meet these requirements, in 2005 theNational Telecommunications and Information Administration ruled that registrants ofus domains may not secure private domain name registration via anonymizing proxies, and that their contact information must be made public.[28] Registrants are required to provide complete contact information without omissions.[29]
Under the locality namespace, delegated managers may impose additional requirements.[10] For example, the former Texas Regional Hostmaster restricted each of its delegated localities to organizations that had a mailing address in that locality.[30]
Other top-level domains related to the United States
Somesponsored top-level domains (sTLDs) are restricted to U.S.-based entities, other than some grandfathered registrations. These domains are much more popular than the equivalent domains underus.
Territories of the United States use their own country code top-level domains (ccTLDs). Identical domains are reserved underus but in practice go unused.
Some U.S. cities are the focus ofgeneric top-level domains under theNew gTLD Program. These gTLDs are not necessarily affiliated with the delegated managers of the corresponding third-level domains within theus locality namespace.
Unofficially, some ccTLDs belonging to other countries are used by U.S.-based private organizations and state government agencies based on their similarity topostal state abbreviations or informal city name abbreviations.
