Top-Level Domain

The domain name system allows users to refer to websites and other Internet resources using names rather than the all-numeric IP addresses assigned to each computer on the Internet. Each domain name consists of a series of character strings separated by dots. The right-most string is the top-level domain (TLD). Every TLD is managed by a single registry.

IANA currently lists the following eligible categories of TLDs:

• Strings eligible under ICANN Board Resolution 00.74 (currently this category applies to only one domain, .eu);
• "Grandfathered" TLDs from prior to 2000, based on "exceptionally reserved" codes in the ISO 3166-1 standard (this category currently applies to two TLDs - .uk and .ac);
• Infrastructure domain (.ARPA); and

TLD Growth - Overview from 1983 to 2021

Dates	TLDs	Use	Reason	Significance
1983	.no	country code TLD	Restricted to use by entities in Norway	The first two-letter country code based on the ISO 3166-1
October 1984	.com, .net, .org	Open	Any person or entity is permitted to register a domain name using these TLDs	The first gTLDs
October 1984	.edu, .gov, .mil	Limited; an entity has sponsored the operation of this TLD	For higher educational institutions, United States governmental entities and agencies, and divisions, services and agencies of the United States Department of Defense, respectively	The first gTLDs
1985	.us, .uk .il	ccTLDs	USA, UK, Israel	The second, third, and fourth ccTLDs
1986	.au, .de, .fi, .fr, .is, .kr, .nl, .se	ccTLDs	Australia, Denmark, Finland, France, Iceland, South Korea, Netherlands, Sweden	The next eight ccTLDs
November 3, 1988	.int	Limited; sponsored	For organizations, offices, and programs endorsed by a treaty between two or more nations	In response to a request by NATO
March 1994				Jon Postel's RFC 1591 establishes the baseline standards for eligible TLDs.
1996				Jon Postel drafts "New Registries and the Delegation of International Top Level Domains"
1998				Domain deregulation; ICANN is formed to oversee Internet names and numbers
May 2000	.arpa	Limited; sponsored	All Internet infrastructure databases	one of the original TLDs, .arpa is re-designated at this time as an Address and Routing Parameter Area, critical to maintaining the stability of the Internet
November 16, 2000	.aero, .biz, .coop, .info, .museum, .name, .pro	Sponsored gTLDs
June 29, 2006		Test domains	per ICANN Board Resolution 07.47	eleven such domains have been delegated thus far
2007	.cat, .eu, .asia	Sponsored specifically for a cultural, ethnic, or regional group	Represents Catalan language and culture, the countries in the European Union, and the Asian continent, respectively	The first TLDs to denote geographical, geopolitical, ethnic, social, or cultural representation
October 30, 2009				IDN ccTLD Fast Track Process is approved by the ICANN Board
	.jobs, .mobi, .tel, .travel	limited to entities having something to do with the phrase comprising the TLD in question
May 5, 2010	مصر السعودية امارات	IDN ccTLDs	From right to left, for Egypt, Saudi Arabia, and the United Arab Emirates	For the first time in the history of the Internet, non-Latin characters are being used for top-level domains
April 2011	.xxx	Sponsored gTLD		ICM Registry had submitted proposals for this sTLD for pornographic sites since 2000
June 20, 2011				ICANN Board votes to dramatically increase the number of gTLDs from the 22 already in operation
January 12, 2012		community or standard	applicant decides if the nTLD is for a defined community consisting of a restricted population; the distinction between sponsored/unsponsored TLDs is deemed irrelevant to this round of nTLDs	The application window for All New gTLD Applications opens
June 13, 2012	--	--	--	Reveal Day: 1,930 applications for new gTLDs submitted; 751 of which were contested
July 15, 2013	.сайт, .онлайн, .شبكة, .游戏	--	--	First four IDN nTLD aggreements signed
November 9, 2014	--	--	--	400th gTLD was delegated
20 May 2017	ccTLDs	--	--	255 ccTLDs delegated
June 2020	IDN ccTLDs	--	--	61 IDN ccTLDs approved
March 2021	--	--	--	IANA lists 1589 TLDs (1503 in use, 67 not assigned/revoked, 8 retired, 11 test domains)

Varieties of TLDs

There are different types of TLDs.

gTLDs

• brand TLDs - corporations use their corporate name as their website's top-level identifier instead of .com or .biz domain space
• community TLDs relate to local events, gatherings, or organizations.
• geoTLDs represent geographical or regional areas that are not countries with three or more ASCII characters.
• hSTLDs
• nTLDs - domains that were introduced beginning in October 2013
• sTLDs - has a sponsor for a specific purpose, such as to represent a specific ethnic community, professional group, or geographical location.

ccTLDs

Country-code TLDs are delegated to a designated ccTLD registry, which is operated by a ccTLD Manager, according to local policies that are adapted to meet the economic, cultural, linguistic, and legal circumstances of the country or territory involved.

• ccTLDs with ASCII characters

TLDs with two ASCII characters have been established for over 250 countries and external territories.

• IDN ccTLDs

TLDs with non-ASCII characters designated for a country or geographic region.

Operating Mode

TLDs operate in different manners but can be categorized in some simple ways:

• Open - Operating and offering both registration and resolution services.
• Closed - Not accepting registrations, may be resolving evergreen/legacy/infrastructure subdomains.

Level of Restriction

• Unrestricted - If there are no requirements that must be met in order to register a name under a TLD, that TLD is Unrestricted.
• Restricted - Requiring Local Physical Address, Local Tax ID, or other specific criteria to qualify.

Reserved Names

• country code top-level domains
• related to ICANN
• related to IANA functions
• names of countries and territories
• names of international and intergovernmental organizations
• names that a registry operator uses to operate the gTLD