A top-level domain (TLD) is one of the
domains at the highest level in the hierarchical
Domain Name System
The Domain Name System (DNS) is a hierarchical and distributed naming system for computers, services, and other resources in the Internet or other Internet Protocol (IP) networks. It associates various information with domain names assigned to ...
of the
Internet
The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, pub ...
after the root domain.
The top-level domain names are installed in the
root zone of the name space. For all domains in lower levels, it is the last part of the
domain name
A domain name is a string that identifies a realm of administrative autonomy, authority or control within the Internet. Domain names are often used to identify services provided through the Internet, such as websites, email services and more. As ...
, that is, the last non empty label of a
fully qualified domain name
A fully qualified domain name (FQDN), sometimes also referred to as an ''absolute domain name'', is a domain name that specifies its exact location in the tree hierarchy of the Domain Name System (DNS). It specifies all domain levels, including th ...
. For example, in the domain name
www.example.com, the top-level domain is
.com
The domain name .com is a top-level domain (TLD) in the Domain Name System (DNS) of the Internet. Added at the beginning of 1985, its name is derived from the word ''commercial'', indicating its original intended purpose for domains registere ...
. Responsibility for management of most top-level domains is delegated to specific organizations by the
ICANN
The Internet Corporation for Assigned Names and Numbers (ICANN ) is an American multistakeholder group and nonprofit organization responsible for coordinating the maintenance and procedures of several databases related to the namespaces ...
, an Internet multi-stakeholder community, which operates the
Internet Assigned Numbers Authority
The Internet Assigned Numbers Authority (IANA) is a standards organization that oversees global IP address allocation, autonomous system number allocation, root zone management in the Domain Name System (DNS), media types, and other Interne ...
(IANA), and is in charge of maintaining the
DNS root zone
The DNS root zone is the top-level DNS zone in the hierarchical namespace of the Domain Name System (DNS) of the Internet.
Before October 1, 2016, the root zone had been overseen by the Internet Corporation for Assigned Names and Numbers (ICANN) ...
.
History
Originally, the top-level domain space was organized into three main groups: ''Countries'', ''Categories'', and ''Multiorganizations''.
An additional ''temporary'' group consisted of only the initial DNS domain,
arpa, and was intended for transitional purposes toward the stabilization of the domain name system.
Types
IANA distinguishes the following groups of top-level domains:
*
Infrastructure top-level domain
A top-level domain (TLD) is one of the domains at the highest level in the hierarchical Domain Name System of the Internet after the root domain. The top-level domain names are installed in the root zone of the name space. For all domains in ...
(ARPA): This group consists of one domain, the
Address and Routing Parameter Area. It is managed by IANA on behalf of the
Internet Engineering Task Force
The Internet Engineering Task Force (IETF) is a standards organization for the Internet and is responsible for the technical standards that make up the Internet protocol suite (TCP/IP). It has no formal membership roster or requirements and a ...
for various purposes specified in the
Request for Comments
A Request for Comments (RFC) is a publication in a series from the principal technical development and standards-setting bodies for the Internet, most prominently the Internet Engineering Task Force (IETF). An RFC is authored by individuals or g ...
publications.
*
Generic top-level domain
Generic top-level domains (gTLDs) are one of the categories of top-level domains (TLDs) maintained by the Internet Assigned Numbers Authority (IANA) for use in the Domain Name System of the Internet. A top-level domain is the last level of eve ...
s (gTLD): Top-level domains with three or more characters
* Generic restricted top-level domains (grTLD): These domains are managed under official ICANN accredited registrars.
*
Sponsored top-level domain A sponsored top-level domain (sTLD) is one of the categories of top-level domains (TLDs) maintained by the Internet Assigned Numbers Authority (IANA) for use in the Domain Name System of the Internet, alongside country-code top-level domains (ccTLD) ...
s (sTLD): These domains are proposed and sponsored by private agencies or organizations that establish and enforce rules restricting the eligibility to use the TLD. Use is based on community theme concepts; these domains are managed under official ICANN accredited registrars.
*
country-code top-level domain
A country code top-level domain (ccTLD) is an Internet top-level domain generally used or reserved for a country, sovereign state, or dependent territory identified with a country code. All ASCII ccTLD identifiers are two letters long, and all t ...
s (ccTLD): Two-letter domains established for
countries
A country is a distinct part of the world, such as a state (polity), state, nation, or other polity, political entity. It may be a sovereign state or make up one part of a larger state. For example, the country of Japan is an independent, so ...
or
territories
A territory is an area of land, sea, or space, particularly belonging or connected to a country, person, or animal.
In international politics, a territory is usually either the total area from which a state may extract power resources or an ...
. With some historical exceptions, the code for any territory is the same as its two-letter
ISO 3166
ISO 3166 is a standard published by the International Organization for Standardization (ISO) that defines codes for the names of countries, dependent territories, special areas of geographical interest, and their principal subdivisions (e.g., ...
code.
**
Internationalized country code top-level domain
An internationalized country code top-level domain is a top-level domain in the Domain Name System (DNS) of the Internet. IDN ccTLDs are specially encoded domain names that are displayed in an end user application, such as a web browser, in the ...
s (IDN ccTLD): ccTLDs in non-Latin character sets (e.g., Arabic, Cyrillic, Greek, Hebrew, or Chinese).
*
Test top-level domains (tTLD): These domains were installed under
.test
The name test is a top-level domain (TLD) that is intended for use in the testing of software. The name was reserved by the Internet Engineering Task Force (IETF) in RFC 2606 (June 1999) and is not intended to ever be installed into the global Dom ...
for testing purposes in the IDN development process; these domains are not present in the root zone.
Countries are designated in the Domain Name System by their
two-letter ISO country code; there are exceptions, however (e.g.,
.uk
.uk is the Internet country code top-level domain (ccTLD) for the United Kingdom. It was first registered in July 1985, seven months after the original generic top-level domains such as .com and the first country code after .us.
, it is the fift ...
). This group of domains is therefore commonly known as
country-code top-level domain
A country code top-level domain (ccTLD) is an Internet top-level domain generally used or reserved for a country, sovereign state, or dependent territory identified with a country code. All ASCII ccTLD identifiers are two letters long, and all t ...
s (ccTLD). Since 2009, countries with non–Latin-based scripts may apply for
internationalized country code top-level domain
An internationalized country code top-level domain is a top-level domain in the Domain Name System (DNS) of the Internet. IDN ccTLDs are specially encoded domain names that are displayed in an end user application, such as a web browser, in the ...
names, which are displayed in end-user applications in their language-native script or alphabet, but use a
Punycode
Punycode is a representation of Unicode with the limited ASCII character subset used for Internet hostnames. Using Punycode, host names containing Unicode characters are transcoded to a subset of ASCII consisting of letters, digits, and hyphens, wh ...
-translated ASCII domain name in the Domain Name System.
Generic top-level domains (formerly ''categories'') initially consisted of
gov
A government is the system or group of people governing an organized community, generally a state.
In the case of its broad associative definition, government normally consists of legislature, executive, and judiciary. Government is a ...
,
edu,
com
Com or COM may refer to:
Computing
* COM (hardware interface), a serial port interface on IBM PC-compatible computers
* COM file, or .com file, short for "command", a file extension for an executable file in MS-DOS
* .com, an Internet top-level d ...
,
mil,
org, and
net
Net or net may refer to:
Mathematics and physics
* Net (mathematics), a filter-like topological generalization of a sequence
* Net, a linear system of divisors of dimension 2
* Net (polyhedron), an arrangement of polygons that can be folded up ...
. More generic TLDs have been added, such as
info
Info is shorthand for "information". It may also refer to:
Computing
* .info, a generic top-level domain
* info:, a URI scheme for information assets with identifiers in public namespaces
* info (Unix), a command used to view documentation produc ...
.
The authoritative
list of current TLDs in the root zone is published at the IANA website a
https://www.iana.org/domains/root/db/
Internationalized country code TLDs
An
internationalized country code top-level domain
An internationalized country code top-level domain is a top-level domain in the Domain Name System (DNS) of the Internet. IDN ccTLDs are specially encoded domain names that are displayed in an end user application, such as a web browser, in the ...
(IDN ccTLD) is a top-level domain with a specially encoded domain name that is displayed in an end user application, such as a
web browser
A web browser is application software for accessing websites. When a user requests a web page from a particular website, the browser retrieves its files from a web server and then displays the page on the user's screen. Browsers are used on ...
, in its language-native script or
alphabet
An alphabet is a standardized set of basic written graphemes (called letters) that represent the phonemes of certain spoken languages. Not all writing systems represent language in this way; in a syllabary, each character represents a syll ...
(such as the
Arabic alphabet), or a non-alphabetic
writing system
A writing system is a method of visually representing verbal communication, based on a script and a set of rules regulating its use. While both writing and speech are useful in conveying messages, writing differs in also being a reliable form ...
(such as
Chinese character
Chinese characters () are logograms developed for the Written Chinese, writing of Chinese. In addition, they have been adapted to write other East Asian languages, and remain a key component of the Japanese writing system where they are k ...
s). IDN ccTLDs are an application of the
internationalized domain name
An internationalized domain name (IDN) is an Internet domain name that contains at least one label displayed in software applications, in whole or in part, in non-latin script or alphabet, such as Arabic, Bengali, Chinese (Mandarin, simplified ...
(IDN) system to top-level Internet domains assigned to countries, or independent geographic regions.
ICANN started to accept applications for IDN ccTLDs in November 2009, and installed the first set into the Domain Names System in May 2010. The first set was a group of Arabic names for the countries of Egypt, Saudi Arabia, and the United Arab Emirates. By May 2010, 21 countries had submitted applications to ICANN, representing 11 scripts.
Infrastructure domain
The domain
arpa was the first Internet top-level domain. It was intended to be used only temporarily, aiding in the transition of traditional ARPANET host names to the domain name system. However, after it had been used for
reverse DNS lookup
In computer networks, a reverse DNS lookup or reverse DNS resolution (rDNS) is the querying technique of the Domain Name System (DNS) to determine the domain name associated with an IP address – the reverse of the usual "forward" DNS lookup o ...
, it was found impractical to retire it, and is used today exclusively for Internet infrastructure purposes such as in-addr.arpa for
IPv4
Internet Protocol version 4 (IPv4) is the fourth version of the Internet Protocol (IP). It is one of the core protocols of standards-based internetworking methods in the Internet and other packet-switched networks. IPv4 was the first version de ...
and ip6.arpa for IPv6 reverse DNS resolution, uri.arpa and urn.arpa for the
Dynamic Delegation Discovery System The Dynamic Delegation Discovery System (DDDS) is an algorithm for applying string transformation rules to application-unique strings to extract specific syntax elements. It is used for finding information, such as authoritative domain name servers, ...
, and e164.arpa for
telephone number mapping
Telephone number mapping is a system of unifying the international telephone number system of the public switched telephone network with the Internet addressing and identification name spaces. Internationally, telephone numbers are systematically ...
based on
NAPTR DNS records. For historical reasons,
arpa is sometimes considered to be a generic top-level domain.
Reserved domains
A set of domain names is reserved by the Internet Engineering Task Force as
special-use domain name
A special-use domain name is a domain name that is defined and reserved in the hierarchy of the Domain Name System of the Internet for special purposes. The designation of a reserved special-use domain is authorized by the Internet Engineering Task ...
s per authority of Request for Comments (RFC) 6761. The practice originated in RFC 1597 for reserved address allocations in 1994, and reserved top-level domains in RFC 2606 of 1999. RFC 6761 reserves the following four top-level domain names to avoid confusion and conflict.
[RFC 6761, ''Special-Use Domain Names'', S. Cheshire, M. Krochmal, The Internet Society (February 2013)] Any such reserved usage of those TLDs should not occur in production networks that utilize the global domain name system:
*
example
Example may refer to:
* '' exempli gratia'' (e.g.), usually read out in English as "for example"
* .example, reserved as a domain name that may not be installed as a top-level domain of the Internet
** example.com, example.net, example.org, ex ...
: reserved for use in examples
*
invalid
Invalid may refer to:
* Patient, a sick person
* one who is confined to home or bed because of illness, disability or injury (sometimes considered a politically incorrect term)
* .invalid, a top-level Internet domain not intended for real use
As t ...
: reserved for use in invalid domain names
*
localhost
In computer networking, localhost is a hostname that refers to the current device used to access it. It is used to access the network services that are running on the host via the loopback network interface. Using the loopback interface bypasses a ...
: reserved to avoid conflict with the traditional use of
localhost
In computer networking, localhost is a hostname that refers to the current device used to access it. It is used to access the network services that are running on the host via the loopback network interface. Using the loopback interface bypasses a ...
as a hostname
*
test
Test(s), testing, or TEST may refer to:
* Test (assessment), an educational assessment intended to measure the respondents' knowledge or other abilities
Arts and entertainment
* ''Test'' (2013 film), an American film
* ''Test'' (2014 film), ...
: reserved for use in tests
RFC 6762 reserves the use of
.local
The domain name .local is a special-use domain name reserved by the Internet Engineering Task Force (IETF) so that it may not be installed as a top-level domain in the Domain Name System (DNS) of the Internet. As such it is similar to the other ...
for link-local host names that can be resolved via the
Multicast DNS
In computer networking, the multicast DNS (mDNS) protocol resolves hostnames to IP addresses within small networks that do not include a local name server. It is a Zero-configuration_networking#Name_service_discovery, zero-configuration service, u ...
name resolution protocol.
RFC 7686 reserves the use of
.onion
.onion is a special-use top level domain name designating an anonymous onion service, which was formerly known as a "hidden service", reachable via the Tor network. Such addresses are not actual DNS names, and the .onion TLD is not in the I ...
for the self-authenticating names of
Tor
Tor, TOR or ToR may refer to:
Places
* Tor, Pallars, a village in Spain
* Tor, former name of Sloviansk, Ukraine, a city
* Mount Tor, Tasmania, Australia, an extinct volcano
* Tor Bay, Devon, England
* Tor River, Western New Guinea, Indonesia
Sc ...
onion services
Tor, short for The Onion Router, is free and open-source software for enabling anonymous communication. It directs Internet traffic through a free, worldwide, volunteer overlay network, consisting of more than seven thousand relays, to conc ...
. These names can only be resolved by a Tor client because of the use of
onion routing
Onion routing is a technique for anonymous communication over a computer network. In an onion network, messages are encapsulated in layers of encryption, analogous to layers of an onion. The encrypted data is transmitted through a series of net ...
to protect the anonymity of users.
Internet-Draf
draft-wkumari-dnsop-internal-00proposes reserving the use of .internal for "names which do not have meaning in the global context but do have meaning in a context internal to their network", and for which the RFC 6761 reserved names are semantically inappropriate.
Historical domains
In the late 1980s,
InterNIC
The Network Information Center (NIC), also known as InterNIC from 1993 until 1998, was the organization primarily responsible for Domain Name System (DNS) domain name allocations and X.500 directory services. From its inception in 1972 until O ...
created the
nato
The North Atlantic Treaty Organization (NATO, ; french: Organisation du traité de l'Atlantique nord, ), also called the North Atlantic Alliance, is an intergovernmental military alliance between 30 member states – 28 European and two No ...
domain for use by
NATO
The North Atlantic Treaty Organization (NATO, ; french: Organisation du traité de l'Atlantique nord, ), also called the North Atlantic Alliance, is an intergovernmental military alliance between 30 member states – 28 European and two No ...
. NATO considered none of the then-existing TLDs as adequately reflecting their status as an
international organization
An international organization or international organisation (see spelling differences), also known as an intergovernmental organization or an international institution, is a stable set of norms and rules meant to govern the behavior of states an ...
. Soon after this addition, however, InterNIC also created the
int TLD for the use by international organizations in general, and persuaded NATO to use the second level domain ''nato.int'' instead. The ''nato'' TLD, no longer used, was finally removed in July 1996.
Other historical TLDs are
cs for
Czechoslovakia
, rue, Чеськословеньско, , yi, טשעכאסלאוואקיי,
, common_name = Czechoslovakia
, life_span = 1918–19391945–1992
, p1 = Austria-Hungary
, image_p1 ...
(now using
cz for
Czech Republic
The Czech Republic, or simply Czechia, is a landlocked country in Central Europe. Historically known as Bohemia, it is bordered by Austria to the south, Germany to the west, Poland to the northeast, and Slovakia to the southeast. The ...
and
sk for
Slovakia
Slovakia (; sk, Slovensko ), officially the Slovak Republic ( sk, Slovenská republika, links=no ), is a landlocked country in Central Europe. It is bordered by Poland to the north, Ukraine to the east, Hungary to the south, Austria to the s ...
),
dd for
East Germany
East Germany, officially the German Democratic Republic (GDR; german: Deutsche Demokratische Republik, , DDR, ), was a country that existed from its creation on 7 October 1949 until its dissolution on 3 October 1990. In these years the state ...
(using
de after
reunification of Germany
German reunification (german: link=no, Deutsche Wiedervereinigung) was the process of re-establishing Germany as a united and fully sovereign state, which took place between 2 May 1989 and 15 March 1991. The day of 3 October 1990 when the Ge ...
),
yu for
SFR Yugoslavia
The Socialist Federal Republic of Yugoslavia, commonly referred to as SFR Yugoslavia or simply as Yugoslavia, was a country in Central and Southeast Europe. It emerged in 1945, following World War II, and lasted until 1992, with the breakup of Yug ...
and
Serbia and Montenegro
Serbia and Montenegro ( sr, Cрбија и Црна Гора, translit=Srbija i Crna Gora) was a country in Southeast Europe located in the Balkans that existed from 1992 to 2006, following the breakup of the Socialist Federal Republic of Yu ...
(now using
ba for
Bosnia and Herzegovina
Bosnia and Herzegovina ( sh, / , ), abbreviated BiH () or B&H, sometimes called Bosnia–Herzegovina and often known informally as Bosnia, is a country at the crossroads of south and southeast Europe, located in the Balkans. Bosnia and H ...
,
hr for
Croatia
, image_flag = Flag of Croatia.svg
, image_coat = Coat of arms of Croatia.svg
, anthem = "Lijepa naša domovino"("Our Beautiful Homeland")
, image_map =
, map_caption =
, capit ...
,
me for
Montenegro
)
, image_map = Europe-Montenegro.svg
, map_caption =
, image_map2 =
, capital = Podgorica
, coordinates =
, largest_city = capital
, official_languages = M ...
,
mk for
North Macedonia
North Macedonia, ; sq, Maqedonia e Veriut, (Macedonia before February 2019), officially the Republic of North Macedonia,, is a country in Southeast Europe. It gained independence in 1991 as one of the successor states of Socialist Feder ...
,
rs for
Serbia
Serbia (, ; Serbian language, Serbian: , , ), officially the Republic of Serbia (Serbian language, Serbian: , , ), is a landlocked country in Southeast Europe, Southeastern and Central Europe, situated at the crossroads of the Pannonian Bas ...
and
si for
Slovenia
Slovenia ( ; sl, Slovenija ), officially the Republic of Slovenia (Slovene: , abbr.: ''RS''), is a country in Central Europe. It is bordered by Italy to the west, Austria to the north, Hungary to the northeast, Croatia to the southeast, an ...
), and
zr for
Zaire
Zaire (, ), officially the Republic of Zaire (french: République du Zaïre, link=no, ), was a Congolese state from 1971 to 1997 in Central Africa that was previously and is now again known as the Democratic Republic of the Congo. Zaire was, ...
(now
cd for the
Democratic Republic of the Congo
The Democratic Republic of the Congo (french: République démocratique du Congo (RDC), colloquially "La RDC" ), informally Congo-Kinshasa, DR Congo, the DRC, the DROC, or the Congo, and formerly and also colloquially Zaire, is a country in ...
). In contrast to these, the TLD
su has remained active despite the demise of the
Soviet Union
The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen national ...
that it represents. Under the chairmanship of
Nigel Roberts
Dr Nigel Roberts FIoD FBCS FRSA is a British computer scientist.
Early life
Roberts was born in Liverpool and grew up in Lancashire.
Education
Educated at Wigan and Prescot Grammar Schools, he received his first degree in Computer Science f ...
,
ICANN
The Internet Corporation for Assigned Names and Numbers (ICANN ) is an American multistakeholder group and nonprofit organization responsible for coordinating the maintenance and procedures of several databases related to the namespaces ...
's
ccNSO
The Country Code Names Supporting Organization (ccNSO) of the Internet Corporation for Assigned Names and Numbers (ICANN) is the policy-development body for a narrow range of global issues regarding country code top-level domain
A country code t ...
is working on a policy for retirement of
ccTLD
A country code top-level domain (ccTLD) is an Internet top-level domain generally used or reserved for a country, sovereign state, or dependent territory identified with a country code. All ASCII ccTLD identifiers are two letters long, and all t ...
s that have been removed from
ISO 3166
ISO 3166 is a standard published by the International Organization for Standardization (ISO) that defines codes for the names of countries, dependent territories, special areas of geographical interest, and their principal subdivisions (e.g., ...
.
Proposed domains
Around late 2000,
ICANN
The Internet Corporation for Assigned Names and Numbers (ICANN ) is an American multistakeholder group and nonprofit organization responsible for coordinating the maintenance and procedures of several databases related to the namespaces ...
discussed and finally introduced
aero
Aero is a Greek prefix relating to flight and air. In British English, it is used as an adjective related to flight (e.g., as a shortened substitute for aeroplane).
Aero, Ærø, or Aeros may refer to:
Aeronautics Airlines and companies
* Aero (P ...
,
biz,
coop
Coop, COOP, Co-op, or ''variation'', most often refers to:
* A chicken coop or other enclosure
* Cooperative or co-operative ("co-op"), an association of persons who cooperate for their mutual social, economic, and cultural benefit
** Housing ...
,
info
Info is shorthand for "information". It may also refer to:
Computing
* .info, a generic top-level domain
* info:, a URI scheme for information assets with identifiers in public namespaces
* info (Unix), a command used to view documentation produc ...
,
museum
A museum ( ; plural museums or, rarely, musea) is a building or institution that cares for and displays a collection of artifacts and other objects of artistic, cultural, historical, or scientific importance. Many public museums make these ...
,
name
A name is a term used for identification by an external observer. They can identify a class or category of things, or a single thing, either uniquely, or within a given context. The entity identified by a name is called its referent. A personal ...
, and
pro
Pro is an abbreviation meaning "professional".
Pro, PRO or variants thereof may also refer to:
People
* Miguel Pro (1891–1927), Mexican priest
* Pro Hart (1928–2006), Australian painter
* Mlungisi Mdluli (born 1980), South African retired f ...
TLDs. Site owners argued that a similar TLD should be made available for adult and pornographic websites to settle the dispute of obscene content on the Internet, to address the responsibility of US service providers under the US
Communications Decency Act
The Communications Decency Act of 1996 (CDA) was the United States Congress's first notable attempt to regulate pornographic material on the Internet. In the 1997 landmark case ''Reno v. ACLU'', the United States Supreme Court unanimously struck ...
of 1996. Several options were proposed including ''xxx'', ''sex'' and ''adult''. The
xxx
XXX may refer to:
Codes and symbols
* 30 (number), Roman numeral XXX
* XXX, designating pornography
** XXX, an X rating#United_States, X rating
** .xxx, an internet top-level domain intended for pornographic sites
* XXX, a symbol of the straight ...
top-level domain eventually went live in 2011.
An older proposal consisted of seven new gTLDs: arts, firm,
info
Info is shorthand for "information". It may also refer to:
Computing
* .info, a generic top-level domain
* info:, a URI scheme for information assets with identifiers in public namespaces
* info (Unix), a command used to view documentation produc ...
, nom, rec,
shop
Shop or shopping refers to:
Business and commerce
* A casual word for a commercial establishment or for a place of business
* Machine shop, a workshop for machining
*"In the shop", referring to a car being at an automotive repair shop
*A wood s ...
, and
web
Web most often refers to:
* Spider web, a silken structure created by the animal
* World Wide Web or the Web, an Internet-based hypertext system
Web, WEB, or the Web may also refer to:
Computing
* WEB, a literate programming system created by ...
. Later
biz,
info
Info is shorthand for "information". It may also refer to:
Computing
* .info, a generic top-level domain
* info:, a URI scheme for information assets with identifiers in public namespaces
* info (Unix), a command used to view documentation produc ...
,
museum
A museum ( ; plural museums or, rarely, musea) is a building or institution that cares for and displays a collection of artifacts and other objects of artistic, cultural, historical, or scientific importance. Many public museums make these ...
, and
name
A name is a term used for identification by an external observer. They can identify a class or category of things, or a single thing, either uniquely, or within a given context. The entity identified by a name is called its referent. A personal ...
covered most of these old proposals.
During the 32nd International Public ICANN Meeting in Paris in 2008, ICANN started a new process of TLD naming policy to take a "significant step forward on the introduction of new generic top-level domains". This program envisioned the availability of many new or already proposed domains, as well as a new application and implementation process. Observers believed that the new rules could result in hundreds of new gTLDs being registered.
On 13 June 2012,
ICANN
The Internet Corporation for Assigned Names and Numbers (ICANN ) is an American multistakeholder group and nonprofit organization responsible for coordinating the maintenance and procedures of several databases related to the namespaces ...
announced nearly 2,000 applications for top-level domains, which began installation throughout 2013. The first seven – ''bike'', ''clothing'', ''guru'', ''holdings'', ''plumbing'', ''singles'', and ''ventures'' – were released in 2014.
Rejected domains
ICANN rejected several proposed domains to include
home
A home, or domicile, is a space used as a permanent or semi-permanent residence for one or many humans, and sometimes various companion animals. It is a fully or semi sheltered space and can have both interior and exterior aspects to it. H ...
and
corp Corp may refer to:
Surname
*Aaron Corp (born 1989), American football quarterback
* Brandon Corp (born 1987), American lacrosse player
*Ronald Corp (born 1951), English composer, conductor and Church of England priest
Abbreviation
*Corp., an abbre ...
due to conflicts regarding gTLDs that are in use in internal networks.
Investigation into the conflicts was conducted at ICANN's request by
Interisle Consulting. The resulting report was to become known as the Name Collision issue, which was first reported at ICANN 47.
Dotless domains
![DNS schema](https://upload.wikimedia.org/wikipedia/commons/d/d2/DNS_schema.svg)
Due to the structure of
DNS
The Domain Name System (DNS) is a hierarchical and distributed naming system for computers, services, and other resources in the Internet or other Internet Protocol (IP) networks. It associates various information with domain names assigned to ...
, each node in the tree has its own collection of
records
A record, recording or records may refer to:
An item or collection of data Computing
* Record (computer science), a data structure
** Record, or row (database), a set of fields in a database related to one entity
** Boot sector or boot record, ...
, and since top-level domains are nodes in DNS, they have records of their own. For example, querying ''org'' itself (with a tool such as
dig
Digging, also referred to as excavation, is the process of using some implement such as claws, hands, manual tools or heavy equipment, to remove material from a solid surface, usually soil, sand or rock (geology), rock on the surface of Earth. Di ...
,
host
A host is a person responsible for guests at an event or for providing hospitality during it.
Host may also refer to:
Places
* Host, Pennsylvania, a village in Berks County
People
*Jim Host (born 1937), American businessman
* Michel Host ...
or
nslookup
nslookup (from ''name server lookup'') is a network administration command-line tool for querying the Domain Name System (DNS) to obtain the mapping between domain name and IP address, or other DNS records.
Overview
nslookup was a member of the ...
) returns information on its
nameserver
A name server refers to the server component of the Domain Name System (DNS), one of the two principal namespaces of the Internet. The most important function of DNS servers is the translation (resolution) of human-memorable domain names (example. ...
s:
QUESTION
org. IN ANY
ANSWER
org. 21599 IN NS a0.org.afilias-nst.info.
org. 21599 IN NS a2.org.afilias-nst.info.
org. 21599 IN NS b0.org.afilias-nst.org.
org. 21599 IN NS b2.org.afilias-nst.org.
''Dotless domains'' are top-level domains that take advantage of that fact, and implement
A,
AAAA or
MX DNS records to serve webpages or allow incoming email directly on a TLD – for example, a webpage hosted on ''
http://example/'', or an email address ''user@example''.
ICANN
The Internet Corporation for Assigned Names and Numbers (ICANN ) is an American multistakeholder group and nonprofit organization responsible for coordinating the maintenance and procedures of several databases related to the namespaces ...
and
IAB have spoken out against the practice, classifying it as a security risk among other concerns. ICANN's Security and Stability Advisory Committee (SSAC) additionally claims that
SMTP
The Simple Mail Transfer Protocol (SMTP) is an Internet standard communication protocol for electronic mail transmission. Mail servers and other message transfer agents use SMTP to send and receive mail messages. User-level email clients typical ...
"requires at least two labels in the
FQDN
A fully qualified domain name (FQDN), sometimes also referred to as an ''absolute domain name'', is a domain name that specifies its exact location in the tree hierarchy of the Domain Name System (DNS). It specifies all domain levels, including th ...
of a mail address" and, as such, mail servers would reject emails to addresses with dotless domains.
ICANN has also published a resolution in 2013 that prohibits the creation of dotless domains on
gTLD
Generic top-level domains (gTLDs) are one of the categories of top-level domains (TLDs) maintained by the Internet Assigned Numbers Authority (IANA) for use in the Domain Name System of the Internet. A top-level domain is the last level of eve ...
s.
ccTLD
A country code top-level domain (ccTLD) is an Internet top-level domain generally used or reserved for a country, sovereign state, or dependent territory identified with a country code. All ASCII ccTLD identifiers are two letters long, and all t ...
s, however, fall largely under their respective country's
jurisdiction
Jurisdiction (from Latin 'law' + 'declaration') is the legal term for the legal authority granted to a legal entity to enact justice. In federations like the United States, areas of jurisdiction apply to local, state, and federal levels.
Jur ...
, and not under ICANN's. Because of this, there have been many examples of dotless domains on ccTLDs in spite of ICANN's vocal opposition.
As of August 2021, that is the case of
Anguilla
Anguilla ( ) is a British Overseas Territory in the Caribbean. It is one of the most northerly of the Leeward Islands in the Lesser Antilles, lying east of Puerto Rico and the Virgin Islands and directly north of Saint Martin. The territo ...
's
.ai
.ai is the Internet country code top-level domain (ccTLD) for Anguilla, a British Overseas Territory in the Caribbean. It is administered by the government of Anguilla.
It is popular with companies in and projects related to the artificial int ...
, online at http://ai./ (as a mirror of http://offshore.ai/), and of
Uzbekistan
Uzbekistan (, ; uz, Ozbekiston, italic=yes / , ; russian: Узбекистан), officially the Republic of Uzbekistan ( uz, Ozbekiston Respublikasi, italic=yes / ; russian: Республика Узбекистан), is a doubly landlocked cou ...
's
.uz
.uz is the Internet country code top-level domain ( ccTLD) for Uzbekistan. Registry services were formerly operated by Euracom GmBH, but were later redelegated to UZINFOCOM. Registrations are taken directly at the second level, but the former ...
, online at https://uz./ (as a mirror of https://cctld.uz/, albeit with an invalid certificate). Other ccTLDs with A or AAAA records, as of August 2021, include:
.bh
.bh is the Internet country code top-level domain ( ccTLD) for Bahrain
Bahrain ( ; ; ar, البحرين, al-Bahrayn, locally ), officially the Kingdom of Bahrain, ' is an island country in Western Asia
Western Asia, West Asia, or South ...
,
.cm
.cm is the country code top-level domain (ccTLD) for Cameroon.
The official registrar for .cm domains is ''Netcom.cm'', based in Yaoundé, the capital of Cameroon. ''Netcom.cm Sarl'' was founded in early 2008 as a partner of ANTIC (), the inf ...
,
.pn,
.tk
.tk is the Internet country code top-level domain (ccTLD) for Tokelau, a territory of New Zealand in the South Pacific. It can be registered on the company Freenom.
Overview
Tokelau allows any individual to register domain names. Users and smal ...
,
.va
.va is the Internet country code top-level domain (ccTLD) for the Vatican City State. It is administered by the Vatican Internet Service.
__TOC__
Background
The .va top-level domain was created in 1995 by Archbishop John Patrick Foley of th ...
, and
.ws
.ws is the Internet country code top-level domain (ccTLD) for Samoa. It is administered by SamoaNIC, for the Ministry of Foreign Affairs of the Government of Samoa.
The .ws domain is an abbreviation for "Western Samoa", which was the nation' ...
.
A similar query to ''org''s presented above can be made for ''ai'', which shows A and MX records for the TLD:
QUESTION
ai. IN ANY
ANSWER
ai. 21599 IN A 209.59.119.34
ai. 21599 IN MX 10 mail.offshore.ai.
ai. 21599 IN NS anycastdns1-cz.nic.ai.
ai. 21599 IN NS anycastdns2-cz.nic.ai.
ai. 21599 IN NS pch.whois.ai.
Historically, many other ccTLDs have had A or AAAA records. On 3 September 2013, as reported by the
IETF
The Internet Engineering Task Force (IETF) is a standards organization for the Internet and is responsible for the technical standards that make up the Internet protocol suite (TCP/IP). It has no formal membership roster or requirements and a ...
, they were the following:
.ac
The .ac top-level domain is the Internet country code (ccTLD) for Saint Helena, Ascension and Tristan da Cunha, used primarily for Ascension Island (Saint Helena has its own ccTLD, .sh). It is administered by NIC.AC, a subsidiary of the Inter ...
,
.dk
.dk is the country code top-level domain (ccTLD) for Denmark. The supervision of the .dk top-level domain is handled exclusively by DK Hostmaster. Any new .dk domain name has to be applied for via an approved registrar. Then the domain name appl ...
,
.gg
.gg is the country code top-level domain for the Bailiwick of Guernsey. The domain is administered by Island Networks, who also administer the .je domain for neighbouring territory Jersey. The domain was chosen as other possible codes were al ...
,
.io,
.je
.je is the country code top-level domain for Jersey. The domain is administered by Island Networks, who also administer the .gg domain for neighbouring territory Guernsey. In 2003, a Google Search website was made available for Jersey, which us ...
,
.kh
.kh is the Internet country code top-level domain
(ccTLD) for the Kingdom of Cambodia. It was formerly administered by the Ministry of Post and Telecommunications of Cambodia from 1997. In September 2012, the domain name was transferred to the ...
,
.sh
.sh is the Internet country code top-level domain (ccTLD) for the British Overseas Territory of Saint Helena, Ascension and Tristan da Cunha, although it is primarily used in Saint Helena ( Ascension Island has its own ccTLD, .ac). Registratio ...
,
.tm
.tm is the Internet country code top-level domain (ccTLD) for Turkmenistan. It is operated by Internet Computer Bureau.
Nic.tm offers domain name purchase, registration, management and renewal as well as Internationalized Domain Name registrati ...
,
.to
.to is the Internet country code top-level domain ( ccTLD) of the island kingdom of Tonga.
The government of Tonga sells domains in its ccTLD to any interested party. The .to ccTLD is administered by the Tonga Network Information Center (Tonic). ...
, and
.vi
.vi is the Internet country code top-level domain ( ccTLD) for the U.S. Virgin Islands.
Second-level domains
Second level domains (of more than 2 characters) were only allowed for Virgin Island companies or residents until 2014, when COBEX ...
.
New TLDs
Following a 2014 resolution by ICANN, newly registered TLDs must implement the following A, MX, TXT, and SRV apex DNS records – where
stands for the registered TLD – for at least 90 days:
. 3600 IN MX 10 your-dns-needs-immediate-attention..
. 3600 IN SRV 10 10 0 your-dns-needs-immediate-attention..
. 3600 IN TXT "Your DNS configuration needs immediate attention see https://icann.org/namecollision"
. 3600 IN A 127.0.53.53
This requirement is meant to avoid domain name collisions when new TLDs are registered. For example, programmers may have used custom local domains such as ''foo.bar'' or ''test.dev'', which would both collide with the creation of gTLDs
.bar
.bar is an Internet domain that is specifically geared for bars, pubs and nightclubs, including bar and restaurant guides, critics, delivery services, wine and liquor, and related industries. It is a new gTLD owned by Mexico City-based company Punt ...
in 2014 and
.dev
.dev is a top-level domain name operated by Google. It was proposed in ICANN's new generic top-level domain (gTLD) program, and became available to the general public on March 1, 2019, with an early access period that began on February 19. To inc ...
in 2019. As of August 2021, top-level domains with these special apex records are
.arab,
.cpa,
.politie, and
.watches.
While this does create apex DNS records of type A and MX, they do not qualify as a dotless domain, as the records should not point to real servers. For instance, the A record contains the IP 127.0.53.53, a loopback address (see
IPv4 § Addressing), picked as a mnemonic to indicate a DNS-related problem, as
DNS uses port 53.
Pseudo-domains
Several networks, such as
BITNET
BITNET was a co-operative U.S. university computer network founded in 1981 by Ira Fuchs at the City University of New York (CUNY) and Greydon Freeman at Yale University. The first network link was between CUNY and Yale.
The name BITNET original ...
,
CSNET The Computer Science Network (CSNET) was a computer network that began operation in 1981 in the United States. Its purpose was to extend networking benefits, for computer science departments at academic and research institutions that could not be di ...
, and
UUCP
UUCP is an acronym of Unix-to-Unix Copy. The term generally refers to a suite of computer programs and protocols allowing remote execution of commands and transfer of files, email and netnews between computers.
A command named is one of the prog ...
, existed that were in widespread use among computer professionals and academic users, but were not interoperable directly with the Internet and exchanged mail with the Internet via special email gateways. For relaying purposes on the gateways, messages associated with these networks were labeled with suffixes such as
bitnet
BITNET was a co-operative U.S. university computer network founded in 1981 by Ira Fuchs at the City University of New York (CUNY) and Greydon Freeman at Yale University. The first network link was between CUNY and Yale.
The name BITNET original ...
,
oz,
csnet The Computer Science Network (CSNET) was a computer network that began operation in 1981 in the United States. Its purpose was to extend networking benefits, for computer science departments at academic and research institutions that could not be di ...
, or
uucp
UUCP is an acronym of Unix-to-Unix Copy. The term generally refers to a suite of computer programs and protocols allowing remote execution of commands and transfer of files, email and netnews between computers.
A command named is one of the prog ...
, but these domains did not exist as top-level domains in the public
Domain Name System
The Domain Name System (DNS) is a hierarchical and distributed naming system for computers, services, and other resources in the Internet or other Internet Protocol (IP) networks. It associates various information with domain names assigned to ...
of the Internet.
Most of these networks have long since ceased to exist, and although UUCP still gets significant use in parts of the world where Internet infrastructure has not yet become well established, it subsequently transitioned to using Internet domain names, and pseudo-domains now largely survive as historical relics. One notable exception is the 2007 emergence of
SWIFTNet Mail, which uses the swift pseudo-domain.
The anonymity network
Tor
Tor, TOR or ToR may refer to:
Places
* Tor, Pallars, a village in Spain
* Tor, former name of Sloviansk, Ukraine, a city
* Mount Tor, Tasmania, Australia, an extinct volcano
* Tor Bay, Devon, England
* Tor River, Western New Guinea, Indonesia
Sc ...
formerly used the top-level pseudo-domain
onion
An onion (''Allium cepa'' L., from Latin ''cepa'' meaning "onion"), also known as the bulb onion or common onion, is a vegetable that is the most widely cultivated species of the genus ''Allium''. The shallot is a botanical variety of the onion ...
for
Tor hidden service
Tor, short for The Onion Router, is free and open-source software for enabling anonymous communication. It directs Internet traffic through a free, worldwide, volunteer overlay network, consisting of more than seven thousand relays, to conc ...
s, which can only be reached with a Tor client because it uses the Tor
onion routing
Onion routing is a technique for anonymous communication over a computer network. In an onion network, messages are encapsulated in layers of encryption, analogous to layers of an onion. The encrypted data is transmitted through a series of net ...
protocol to reach the hidden service to protect the anonymity of users. However, the pseudo-domain became officially reserved in October 2015.
i2p
The Invisible Internet Project (I2P) is an anonymous network layer (implemented as a mix network) that allows for censorship-resistant, peer-to-peer communication. Anonymous connections are achieved by encrypting the user's traffic (by using ...
provides a similar hidden pseudo-domain, .i2p.
BT hubs use the top-level pseudo-domain .home for local DNS resolution of routers, modems and gateways.
See also
*
List of Internet top-level domains
This list of Internet top-level domains (TLD) contains top-level domains, which are those domains in the DNS root zone of the Domain Name System of the Internet. A list of the top-level domains by the Internet Assigned Numbers Authority (IANA) ...
*
Alternative DNS root
The Internet uses the Domain Name System (DNS) to associate numeric computer IP addresses with human-readable names. The top level of the domain name hierarchy, the DNS root, contains the top-level domains that appear as the suffixes of all Intern ...
*
Domain hack
A domain hack is a domain name that suggests a word, phrase, or name when concatenating two or more adjacent levels of that domain. For example, and , using the fictitious country-code domains ''.ds'' and ''.le'', suggest the words ''birds'' an ...
*
Domain name registrar
A domain name registrar is a company that manages the reservation of Internet domain names. A domain name registrar must be accredited by a generic top-level domain (gTLD) registry or a country code top-level domain (ccTLD) registry. A registrar ...
*
Public Suffix List The Public Suffix List (PSL) is a catalog of certain Internet domain names. Entries on the list are also referred to as effective top-level domains (eTLD).
The Mozilla Foundation initiated the suffix list for the security and privacy policies of its ...
*
Second-level domain
In the Domain Name System (DNS) hierarchy, a second-level domain (SLD or 2LD) is a domain that is directly below a top-level domain (TLD). For example, in , is the second-level domain of the TLD.
Second-level domains commonly refer to the organ ...
References
Further reading
''Addressing the World'' ''National Identity and Internet Country Code Domains'', edited by Erica Schlesinger Wass (Rowman & Littlefield, 2003, ) examines connections between cultures and their ccTLDs.
''Ruling the Root''by Milton Mueller (MIT Press, 2001, ) discusses TLDs and domain name policy more generally.
External links
IANA TLD List IANA List of TLDs on the DNS Root ZoneArticles on CircleID about TLDs*
TLDs accepted in 2012
{{GTLD
Domain Name System
Identifiers
Internet governance