|This article needs additional citations for verification. (June 2012)|
|TLD type||Country code top-level domain|
|Sponsor||United States Department of Commerce|
|Intended use||Entities connected with
|Actual use||Was formerly the primary domain name used by state and local governments in the United States, but many of these have since moved to .GOV.
Some use by American businesses; relatively popular for domain hacks (e.g. del.icio.us) Most businesses and commercial interests use .com instead.
|Registered domains||1,786,848 (Nov 2012)|
|Registration restrictions||U.S. nexus requirement can be enforced by challenge, but seldom is.|
|Structure||Originally registrations were within complex, 3rd or 4th level hierarchy, but currently direct second-level registrations are allowed; kids.us permits 3rd-level registrations for child-friendly sites.|
|Documents||RFC 1480; USDoC agreements with Neustar|
|Dispute policies||usTLD Dispute Resolution Policy (usDRP)|
.us is the Internet country code top-level domain (ccTLD) for the United States and was established in 1985. Registrants of .us domains must be United States citizens, residents, or organizations, or a foreign entity with a presence in the United States. Most registrants in the country have registered for .com, .net, .org and other gTLDs, instead of .us, which has primarily been used by state and local governments despite any entity having the option of registering a .us domain.
The original administrator of .us was Jon Postel of the Information Sciences Institute (ISI) at the University of Southern California (USC). He administered .us under a subcontract that the ISI and USC had from SRI International (which held the .us and the gTLD contract with the United States Department of Defense) and later Network Solutions (which held the .us and the gTLD contract with the National Science Foundation). Registrants could only register third-level domains or higher in a geographic and organizational hierarchy. The vast majority of the geographic subdomains in .us were delegated to various private entities and .us registrants could register with the delegated administrator for the level they wished to register in, but not directly with the .us administrator.
Second-level domains for states
Each U.S. state, federal territory, and the District of Columbia has a reserved two-letter second-level domain based on the International Organization for Standardization Standard ISO 3166-2:US for the United States. For example, .ny.us is reserved for websites affiliated with New York and .va.us for those affiliated with Virginia. However, some state administrations prefer usage of .gov domains or others: e.g. California’s chief website is located at www.ca.gov instead of www.state.ca.us, and Massachusetts' chief website is located at www.mass.gov instead of www.state.ma.us.
Additionally, the territories of the U.S. have their own ccTLDs: .as for American Samoa, .gu for Guam, .mp for Northern Mariana Islands, .pr for Puerto Rico, and .vi for the United States Virgin Islands. These operate alongside or in preference to their .us subdomains (i.e. .as.us, .gu.us, .mp.us, .pr.us, and .vi.us, respectively).
The general format is "<organization-name>.<locality>.<state>.us", where <state> is a state's two-letter postal abbreviation.
Four values of <organization-name> have specific meanings:
- ci: city government agencies (ci.<locality>.<state>.us)
- town: town government agencies (town.<locality>.<state>.us)
- vil: village government agencies (vil.<locality>.<state>.us)
- co: county government agencies (co.<locality>.<state>.us)
Ordinarily, a <locality> is a city, county, parish, or township. Some other names may replace the <locality>:
- state: state government agencies (<organization-name>.state.<state>.us)
- dst: government agencies in administrative districts (<organization-name>.dst.<state>.us)
- cog: councils of government (federations of cities or counties) (<organization-name>.cog.<state>.us)
- k12: public elementary and/or secondary unified school districts (<district-name>.k12.<state>.us), or individual schools (<school-name>.k12.<state>.us)
- pvt.k12: private elementary or secondary schools (<school-name>.pvt.k12.<state>.us)
- cc: community colleges (<school-name>.cc.<state>.us)
- tec: technical and vocational schools (<school-name>.tec.<state>.us)
- lib: public libraries (library-name>.lib.<state>.us)
- mus: museums (<museum-name>.mus.<state>.us)
- gen: general independent entities (clubs or other groups not fitting into the above categories) (<organization-name>.gen.<state>.us)
Small entities like individuals or small businesses can also register locality based .US domain names.
In some cases, <locality> and <state> may be combined into a single namespace. For example, many Kentucky school districts have a name of the form <area>.kyschools.us, and even those districts that have a different URL use that form as a redirect to their actual URL. For two examples in the same Kentucky county, Paducah Public Schools are at http://paducah.kyschools.us, while the McCracken County Public Schools use mccracken.kyschools.us as a redirect to their actual URL of http://www.mccrackencountyschools.net.
As noted above, registration of a subdomain in this space may depend on the cooperation of a private delegate. Many mainstream registration companies do not offer domains in this space, which may account for the low utilization rate.
Restrictions on use of .us domains
Under .US 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 a bona fide presence in the United States
To ensure that these requirements are met, NeuStar frequently conducts "spot checks" on registrant information.
To prevent anonymous registrations that do not meet these requirements, the National Telecommunications and Information Administration has ruled that registrants of .us domains may not secure private domain name registration .
Registrants are required to provide complete contact information without omissions. 
- .us Domain Registry
- .US Locality Domains - A wiki page showing instructions for registering a fourth-level .us locality domain name.
- IANA .us whois information
- Domain Names: Management of Internet Names and Addresses .us Domain Space
- usTLD Nexus Requirements - Requirements for registrants of .us domains
- Kids.us Content Policies
- RFC 1480: The US Domain (June 1993)
- locality-based namespaces