A top-level domain (TLD) is one of the domains at the highest level in the hierarchical Domain Name System of the Internet. 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, that is, the last label of a fully qualified domain name. For example, in the domain name www.example.com, the top-level domain is com. Responsibility for management of most top-level domains is delegated to specific organizations by the Internet Corporation for Assigned Names and Numbers (ICANN), which operates the Internet Assigned Numbers Authority (IANA), and is in charge of maintaining the DNS root zone.
IANA currently distinguishes the following groups of top-level domains:
|For a full list of about 1,500 TLDs, see List of Internet top-level domains.|
|Example domain||Type||Sponsoring institution|
|arpa||Infrastructure||Internet Architecture Board; restricted|
|blue||Generic||Afilias Limited; unrestricted|
|ovh||Generic||OVH SAS; run by AFNIC, unrestricted|
|name||Restricted generic||VeriSign Information Services, Inc.; unrestricted|
|ac||Country-code||Cable and Wireless (Ascension Island); unrestricted|
|zw||Country-code||Postal and Telecommunications Regulatory Authority of Zimbabwe; unrestricted|
|aero||Sponsored||Société Internationale de Télécommunications Aéronautiques; unrestricted|
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.
As of 2015, IANA distinguishes the following groups of top-level domains:
Countries are designated in the Domain Name System by their two-letter ISO country code; there are exceptions, however (e.g., .uk). This group of domains is therefore commonly known as country-code top-level domains (ccTLD). Since 2009, countries with non–Latin-based scripts may apply for internationalized country code top-level domain names, which are displayed in end-user applications in their language-native script or alphabet, but use a Punycode-translated ASCII domain name in the Domain Name System.
An internationalized country code top-level domain (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, in its language-native script or alphabet (such as the Arabic alphabet), or a non-alphabetic writing system (such as Chinese characters). IDN ccTLDs are an application of the internationalized domain name (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.
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, it was found impractical to retire it, and is used today exclusively for Internet infrastructure purposes such as in-addr.arpa for IPv4 and ip6.arpa for IPv6 reverse DNS resolution, uri.arpa and urn.arpa for the Dynamic Delegation Discovery System, and e164.arpa for telephone number mapping based on NAPTR DNS records. For historical reasons, arpa is sometimes considered to be a generic top-level domain.
RFC 6761 reserves the following four top-level domain names to avoid confusion and conflict. Any such reserved usage of those TLDs should not occur in production networks that utilize the global domain name system:
RFC 7686 reserves the use of .onion for the self-authenticating names of Tor hidden services. These names can only be resolved by a Tor client because of the use of onion routing to protect the anonymity of users.
In the late 1980s, InterNIC created the nato domain for use by NATO. NATO considered none of the then existing TLDs as adequately reflecting their status as an international organization. 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 (now using cz for Czech Republic and sk for Slovak Republic), dd for East Germany (using de after reunification of Germany), yu for SFR Yugoslavia (now using ba for Bosnia and Herzegovina, hr for Croatia, me for Montenegro, mk for North Macedonia, rs for Serbia and si for Slovenia), and zr for Zaire (now cd for Democratic Republic of the Congo). In contrast to these, the TLD su has remained active despite the demise of the Soviet Union that it represents. Under the chairmanship of Nigel Roberts, ICANN's ccNSO is working on a policy for retirement of ccTLDs that have been removed from ISO-3166.
Around late 2000, when ICANN discussed and finally introduced aero, biz, coop, info, museum, name, and pro 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 and the responsibility of US service providers under the US Communications Decency Act of 1996. Several options were proposed including xxx, sex and adult. The .xxx domain went live in 2011.
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 announced nearly 2,000 applications for top-level domains, which began installation throughout 2013. Donuts Inc. invested $57 million in more than 300 applications while Famous Four Media applied for 61 new domains. The first seven – bike, clothing, guru, holdings, plumbing, singles, and ventures – were released in 2014.
ICANN's slow progress in creating new generic top-level domains, and the high application costs associated with TLDs, contributed to the creation of alternate DNS roots with different sets of top-level domains. Such domains may be accessed by configuration of a computer with alternate or additional (forwarder) DNS servers or plugin modules for web browsers. Browser plugins detect alternate root domain requests and access an alternate domain name server for such requests.
Several networks, such as BITNET, CSNET, UUCP, 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, oz, csnet, or uucp, but these domains did not exist as top-level domains in the public Domain Name System 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 formerly used the top-level pseudo-domain onion for Tor hidden services, which can only be reached with a Tor client because it uses the Tor onion routing protocol to reach the hidden service to protect the anonymity of users. However, the pseudo-domain became officially reserved in October 2015. i2p 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.
This memo provides some information on the structure of the names in the Domain Name System (DNS), specifically the top-level domain names; and on the administration of domains.
This memo is a policy statement on the implementation of the Domain Style Naming System in the Internet. This memo is an update of RFC-881, and RFC-897. This is an official policy statement of the IAB and the DARPA.
.ac is the Internet country code top-level domain (ccTLD) for Saint Helena, Ascension and Tristan da Cunha. It is administered by NIC.AC, a subsidiary of the Internet Computer Bureau based in the United Kingdom.
Registration for this domain is open to anyone. The registry accepts registrations of internationalized domain names..ac is marketed by some domain-brokers as a domain for the city of Aachen in Germany, using the analogy to the automotive license plate designation ("AC") for the city..com
The domain name com is a top-level domain (TLD) in the Domain Name System of the Internet. Its name is derived from the word commercial, indicating its original intended purpose for domains registered by commercial organizations. Later, the domain opened for general purposes.
The domain was originally administered by the United States Department of Defense, but is today operated by Verisign, and remains under ultimate jurisdiction of U.S. law. Verisign Registrations in the .com domain are processed via registrars accredited by ICANN. The registry accepts internationalized domain names.
The domain was one of the original top-level domains (TLDs) in the Internet when the Domain Name System was implemented in January 1985, the others being edu, gov, mil, net, org, and arpa. It has grown into the largest top-level domain..dz
.dz is the country code top-level domain (ccTLD) for Algeria (from Dzayer, the local name for Algeria).
It is administered by Network Internet Center. DZ, a subdivision of CERIST (Centre de Recherche sur l'Information Scientifique et Technique). To apply for a .dz domain name, one must be an organization with a permanent presence in Algeria, and choose a name of three or more letters. Currently, NIC.DZ charges 1000 Algerian dinars a year (about 14 USD)..gi
.gi is the country code top-level domain (ccTLD) for Gibraltar, a British Overseas Territory..gr
.gr is the country code top-level domain (ccTLD) for Greece. Registrations are processed via accredited registrars and domain names in Greek characters may also be registered..il
.il is the Internet country code top-level domain (ccTLD) of Israel. It is administered by the Israel Internet Association and managed by NIC - ISRAEL, which hosts the DNS Root Server and manages the Israeli Internet Exchange, that supports IPv4 and IPv6.The .il top-level domain is one of the earliest registered ccTLDs. When Israel registered it, on 24 October 1985, it was the third registration of any ccTLD, after .us and .uk, which were registered earlier that year.
As of 10 June 2014 there are 227,066 domain names registered under the .il ccTLD in Israel.Israel is still in the process of getting an internationalized top-level domain, .ישראל..io
The Internet country code top-level domain (ccTLD) .io is assigned to the British Indian Ocean Territory.The .io domain is administered by the Internet Computer Bureau, a domain name registry company based in the United Kingdom.Google's ad targeting treats .io as a generic top-level domain (gTLD) because "users and webmasters frequently see [the domain] more generic than country-targeted.".lt
.LT is the Internet country code top-level domain (ccTLD) for Lithuania..mt
.mt is the Internet country code top-level domain (ccTLD) for Malta..net
The domain name net is a generic top-level domain (gTLD) used in the Domain Name System of the Internet. The name is derived from the word network, indicating it was originally intended for organizations involved in networking technologies, such as Internet service providers and other infrastructure companies. However, restrictions were never enforced and the domain is now a general purpose namespace. It is still popular with network operators and the advertising sector, and it is often treated as an alternative to com.
net is one of the original top-level domains (the other six being com, org, edu, gov, mil, and arpa) despite not being mentioned in RFC 920, having been created in January 1985. As of 2015, it is the fourth most popular top-level domain, after .com, .tk and .de.Verisign, the operator of net after acquiring Network Solutions, held an operations contract that expired on 30 June 2005. ICANN, the organization responsible for domain management, sought proposals from organizations to operate the domain upon expiration of the contract. Verisign regained the contract bid and secured its control over the net registry for another six years.
On 30 June 2011, the contract with Verisign was automatically renewed for another six years. This is because of a resolution approved by the ICANN board, which states that renewal will be automatic as long as Verisign meets certain ICANN requirements.Registrations are processed via accredited registrars and internationalized domain names are also accepted..org
The domain name org is a generic top-level domain (gTLD) of the Domain Name System (DNS) used in the Internet. The name is truncated from organization. It was one of the original domains established in 1985, and has been operated by the Public Interest Registry since 2003. The domain was originally intended for non-profit entities, but this restriction was not enforced and has been removed. The domain is commonly used by schools, open-source projects, and communities, but also by some for-profit entities. The number of registered domains in org has increased from fewer than one million in the 1990s, to ten million as of June 2013..ps
.ps is the Internet country code top-level domain ccTLD officially assigned to the State of Palestine.
It is administered by the Palestinian National Internet Naming Authority.Registrations are processed by certified registrars.
The Internationalized country code top-level domain for the State of Palestine is .فلسطين, which is represented as .xn--ygbi2ammx in Punycode.On 06 February, 2013 the ISO 3166-1 code for the State of Palestine changed to reflect the PS used for the ccTLD..sh
.sh is the Internet country code top-level domain (ccTLD) for Saint Helena, Ascension and Tristan da Cunha, British Overseas Territories. Registrations of internationalized domain names are also accepted.On 22 February, 2010 the ISO 3166-1 code for Saint Helena, Ascension and Tristan da Cunha changed to reflect the SH used for the ccTLD..wf
.wf is the Internet country code top-level domain (ccTLD) for the Wallis and Futuna Islands. This top-level domain is run by the AFNIC and registrations are open to all.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 two-letter top-level domains are ccTLDs. In 2018, the Internet Assigned Numbers Authority (IANA) began implementing internationalized country code top-level domains, consisting of language-native characters when displayed in an end-user application. Creation and delegation of ccTLDs is described in RFC 1591, corresponding to ISO 3166-1 alpha-2 country codes.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, example.edu, second-level domain names reserved for use in documentation as examples
HMS Example (P165), an Archer-class patrol and training vessel of the British Royal NavyGeneric 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 every fully qualified domain name. They are called generic for historic reasons; initially, they were contrasted with country-specific TLDs in RFC 920.
The core group of generic top-level domains consists of the com, info, net, and org domains. In addition, the domains name, and pro are also considered generic; however, these are designated as restricted, because registrations within them require proof of eligibility within the guidelines set for each.Historically, the group of generic top-level domains included domains, created in the early development of the domain name system, that are now sponsored by designated agencies or organizations and are restricted to specific types of registrants. Thus, domains edu, gov, int, and mil are now considered sponsored top-level domains, much like the themed top-level domains (e.g., jobs). The entire group of domains that do not have a geographic or country designation (see country-code top-level domain) is still often referred to by the term generic TLDs.
The number of gTLD as of March 2018 exceeds 1,200 domains.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 their language-native script or alphabet, such as the Arabic alphabet, or a non-alphabetic writing system, such as Chinese characters. IDN ccTLDs are an application of the internationalized domain name system to top-level Internet domains assigned to countries, or independent geographic regions.
Although the domain class uses the term code, some of these ccTLDs are not codes but full words. For example, السعودية (as-Suʻūdiyya) is not an abbreviation of "Saudi Arabia", but the common short-form name of the country in Arabic.
Countries with internationalized ccTLDs also retain their traditional ASCII-based ccTLDs.
As of August 2018 there are 59 approved internationalized country code top-level domains, of them at least 47 used. The most used are .рф (Russia) with over 900,000 domains names, .台灣 (Taiwan) with around 500,000 and .中国 (China) with over 200,000 domains. Still as of 2018 around 20 countries using non-Latin script do not have an internationalized country code top-level domain, including Israel and Japan.Proposed top-level domain
The Domain Name System of the Internet consists of a set of top-level domains which constitute the root domain of the hierarchical name space and database. In the growth of the Internet, it became desirable to expand the set of initially six generic top-level domains in 1984. As a result, new top-level domain names have been proposed for implementation by ICANN. Such proposals included a variety of models ranging from adoption of policies for unrestricted gTLDs that could be registered by anyone for any purpose, to chartered gTLDs for specialized uses by specialized organizations. In October 2000, ICANN published a list of proposals for top-level domain strings it had received.