Top-level domain

from Wikipedia, the free encyclopedia

Top-level domain (English for "top level area", abbreviation TLD ) describes the last section (to the right of the point) of a domain in the Internet and represents the highest level of name resolution . Is the complete domain name of a server or website for example , the letter combination .com on the far right corresponds to the top-level domain of this name.

In the Domain Name System (DNS) the names and thus also the TLDs are referenced and resolved, i.e. assigned to a unique IP address . As part of the domain registration , the domain name registrar creates a database entry about the owner, which enables Whois queries via the protocol of the same name, similar to a telephone book .

The IANA divides TLDs into two main groups and one special case (as of 2019)

The special cases .bitnet and .uucp are no longer in use .

A list of all top-level domains can be found on the IANA website, see section Weblinks “Root Zone Database”.

Generic top-level domains

The generic top-level domains (gTLD) are divided into sponsored (sTLD) and non-sponsored (uTLD). The (much more important) unsponsored domains are under the direct control of ICANN and the Internet Society . The sponsored domains are controlled and financed by independent organizations. These organizations have the right to apply their own guidelines for assigning domain names. One example is .mil. This domain is used exclusively by the US military.

By far the most widely used TLD is .com (approx. 127 million registered domains in September 2017). Originally used by US companies, it is now used around the world.

Unsupported domains (uTLD)

Non-sponsored top-level domains ( English unsponsored top-level domain , abbreviation uTLD ) are used by a certain group. They consist of three or more characters and stand for a term that distinguishes this group.

TLD meaning Eligibility DNSSEC
.arpa arpanet TLD of the original Arpanet , now used as the Address and Routing Parameter Area . The IANA calls this TLD the "infrastructure domain". Yes
.biz business for commercial use only; de facto freely accessible to everyone. Designated generic-restricted by the IANA . Yes
.com commercial originally only for companies , for a long time freely accessible to everyone Yes
.info information intended for information providers , but freely accessible to everyone from the start. Yes
.Surname Surname only for natural persons or families (private individuals); de facto freely accessible to everyone. Designated generic-restricted by the IANA . No
.net network originally for network management institutions, today free for everyone. Yes
.org organization for non-commercial organizations ( non-profit organizations ), free for everyone since 2003. Yes
.Per professionals for “qualified specialists ” (a few professional groups) who identify themselves as such by means of “suitable certificates”. Designated generic-restricted by the IANA . No.

Due to the liberal allocation for the TLDs .com , .net , .org and (with minor restrictions) .biz and (more recently) .name , the original meanings of these TLDs have largely been lost. Such a TLD does not necessarily indicate a corresponding use. For example, the .org TLD, which was actually intended for non-commercial organizations, is now occasionally used by commercial providers. Furthermore, international, non-commercial websites like to use .net (or .org) so that they do not have to fall back on a country-specific TLD or the widespread .com. While .org is now only listed as a generic TLD by the IANA , the TLDs biz , .name and .pro are still classified as generic-restricted for the time being (as of August 2019) .

Sponsored Domains (sTLD)

Sponsored domains ( sponsored top-level domains , abbreviation sTLD ) are proposed by certain companies or organizations that operate these namespaces in accordance with detailed guidelines and also have control and sanction rights with which the intended and lawful use of the registered names is carried out the provider should be ensured. For example, the TLD .aero is sponsored by SITA , which restricts use to aviation content, or the use of .mobi names is tied to the website provider ensuring compliance with certain guidelines for the device-independent use of web content be considered elementary, so that z. B. mobile phones can display this content.

TLD meaning Eligibility sponsor DNSSEC
Existing sponsored domains
.aero aeronautics organizations active in the aviation industry Société Internationale de Télécommunications Aéronautiques No
.asia asia Individuals and companies located within ICANN's Asia / Australia / Pacific region (accessible to everyone since October 2007) Yes
.cat catalan Catalan language and culture Fundació puntCAT Yes
.coop cooperatives Cooperatives Dot Cooperation LLC No
.edu educational since 2001 limited to educational institutions accredited by a United States Department of Education accredited accreditation agency. Apart from a few institutions that already had a .edu domain and grandfathering enjoy are, this almost exclusively US colleges and universities. Yes
.gov government US government bodies only Yes
.int international multinational organizations IANA No
.jobs jobs only companies with vacancies No
.lgbt LGBT * LGBT * community
.mil military US military facilities only Yes
.mobi mobile to identify services that explicitly support use by mobile devices mTLD Top Level Domain Limited No
.museum museum Museums Museum Domain Management Association Yes
.post Office postal Post and logistics company Universal Postal Union Yes
.tel telecommunication standardized storage and publication of contact data; Saves data directly in the Domain Name System as NAPTR and TXT record No
.travel travel Travel industry (e.g. travel agencies, airlines, etc.) No
.xxx sex erotic and sexual content ICM registry No

New domains

On June 26, 2008, ICANN decided to relax the rules for new sponsored domains. In the following months, rules and the application process were developed. On June 20, 2011, ICANN passed an application process for new generic top-level domains (gTLD) in Singapore. Between January 12, 2012 and May 30, 2012, interested parties could apply for a new TLD. On June 13, 2012, the so-called Reveal Day , ICANN published a list of which applicants had submitted applications for which new desired top level domains. In a period of about two years, ICANN wants to examine the proposals and decide on any approvals. Approved and used top-level domains of this new type are for example .berlin , .koeln and .swiss .

Special cases

There are some, mostly historical, special domains or pseudo- domains as well as names reserved for certain purposes, for which no TLD is set up for various reasons:

domain Usage DNSSEC
.arpa Today the domain is used as an infrastructure domain for technical purposes in the DNS and some other tasks and is administered by the IANA . It was originally only intended to be a temporary solution for setting up the DNS on the Internet, but the later resolution of this domain turned out to be impractical. The subdomain is used worldwide to enable the resolution of an IPv4 address into a domain name ( reverse lookup ), with IPv6 is used for the same purpose. Another subdomain,, is used for ENUM , the addressing of Internet services via telephone numbers (keyword Voice-over-IP ). Yes
.bit .bit is a pseudo top level domain of the Namecoin project. It is not approved by ICANN and is therefore not part of the corresponding official DNS. -
.bitnet The domain was used in the early days of the Internet when some technically different networks were operated side by side. It was an IBM- sponsored branch of the network to demonstrate feasibility; the name means b ecause i t’s t ime - net . -
.example According to RFC 2606 , this domain is reserved for examples in texts, documentation and the like. It is not assigned, as are the second-level domains , , . For example, automatically generated links in online documents do not refer to real domains. -
.invalid This domain is reserved by RFC 2606 as an example of a guaranteed non-existent domain. It can be used for software tests, for example . -
.local This domain is used in Multicast DNS for link-local addresses. -
.localhost localhost is used locally on most computers for their loopback device . Therefore, according to RFC 2606, it is not assigned elsewhere, since it would generally not be accessible anyway. -
.nato .nato originally existed for NATO , but was given up after the domain was registered for it. -
.onion .onion is a special-use top-level domain for the use of hidden services (German: hidden services) in the anonymization service The Onion Routing (Tor). The .onion addresses are not part of the DNS, but can be interpreted by applications if they are sent through a proxy into the Tor network. -
.root The domain "vrsn-end-of-zone-marker-dummy-record.root" existed in the root zone until DNSSEC was introduced . The purpose of its existence was a simple test whether the root zone was completely transferred during a zone transfer, which was possible since the domain was the last entry in the zone. -
.test According to RFC 2606 , this domain is reserved for tests and is not officially assigned, but can be used locally. -
.uucp For a long time, this domain was a pseudo-domain in TCP / IP networks for computers in the uucp mapping project that did not have their own internet domain or acted as gateways . As a rule, these computers could only be reached via telephone modem connections or only passively. -

Country-specific top-level domains (ccTLD)

World map with entered ccTLDs

There are over 200 ccTLDs (cc = country code), each country is assigned exactly one two-letter code (ALPHA-2) according to ISO 3166 . In addition, there are often separate ccTLDs for dependent areas, which are mostly geographically separated from the mother country.


  • The UK uses the TLD .uk , although the ISO encoding is GB (GB, GBR, 826). In addition, the ISO also reserved the UK coding as an exception. The .gb TLD is also reserved, but is currently not used, apart from a single registration.
  • The European Union used with .eu a ccTLD, although it is not an independent state. The coding EU was exceptionally reserved with this meaning by the ISO 3166 Maintenance Agency. This was done through a special decision based on an established practical need. In contrast to states, the EU has neither a three-letter nor a three-digit coding. Its member countries will continue to keep their own ccTLDs, and no country-specific subdomains of .eu will be introduced.



Some obsolete TLDs are still active for reasons of availability:


Allocated but unused are currently:

Not yet assigned

The following ccTLDs have not yet been assigned:

  • .bl Saint-Barthélemy
  • .mf Saint-Martin

Conditions of allocation

Every country has the right to set its own allocation guidelines for its domain. The vast majority of these are set up independently by the awarding authorities due to technical necessities and legal requirements and can differ considerably from one another.

For example, in order to register under the French TLD .fr, proof of residence or company headquarters in France (since December 6, 2011 in the European Union) had to be proven.

In Germany , on October 23, 2009, the allocation of one-, two-digit and only digit domains with .de began. Until then, the .de domain had to consist of at least three characters, and one of them had to be a letter. From the early days of the Internet there were three two-digit domains: , and . (The fourth two-letter domain for a long time was no longer registered at the time of the settlement.) Volkswagen sued the Higher Regional Court in Frankfurt am Main for the allocation of the domain , which then went into operation on the key date has been.

In Switzerland , only the cantons have a domain with two characters resulting from the official abbreviation (e.g. , , , ). The domain is also operated by the Federal Chancellery . Apart from these exceptions, Swiss domains must consist of at least three characters. Exceptions are (for the sixth Swiss National Exhibition 2002 ) and the domain of the municipality of Au in the canton of St. Gallen .

In other cases, only a few predefined names are possible for the second name level; the actual name is then defined as a third-level domain (e.g. ). One example was the British .uk domain, which only allowed the following second-level domains until June 9, 2014:

  • - academic , educational institutions such as universities
  • - commercial
  • - government , central and regional government organizations
  • - limited company
  • - presences of individuals
  • - ISPs and other network companies
  • - National Health Service , state health system and its institutions
  • - Network Information Center , for internal network administration only
  • - non-profit organizations
  • - public limited companies (listed companies)
  • - schools

In addition, there are some state-used second-level domains such as , ( Ministry of Defense ), (and - also for the British Library ) or . These come from an earlier time and are grandfathered.


Smaller states or countries affected by poverty, in particular, market their domains by handling their allocation policy very liberally and actively promoting the registration of domains. The domain market is developing into a lucrative business, as the registration fees are sometimes set significantly above the actual costs.


The domain of Colombia is also used instead of the ending .com, for example with the meaning "Company", "Commerce", "Corporation", "Community", "Content", "Connection".


One of the first such states to have their domains freely registered was Tonga with .to in 1998 . The response was very good, because at that time a lot of short and concise domains under .com were no longer available, and other ccTLDs sometimes had very strict registration requirements. In addition resulted from the ending .to interesting domain names well in short URLs could be used as or . Today the TLD .to is happy to torrent or warez sites used, among other reasons, also because the NIC does not allow holders queries so that they can be anonymous domains registered.

Media domains


The .fm TLD of the Federated States of Micronesia is widely used in broadcasting. The abbreviation FM stands for frequency modulation in radio broadcasting , which is used in VHF broadcasting and is usually associated with it.

.in the

The association of an abbreviation is also used, for example, by the websites of some instant messaging services ( IM for short ) whose TLD .im is registered on the Isle of Man , e.g. B. in the instant messenger Pidgin ( ).


Another well-known third-party ccTLD is .tv from the state of Tuvalu , which is marketed as television . For this purpose, a separate company DotTV was founded, which markets the domain and in which the state of Tuvalu is a co-owner. This coup brought the tiny country of 50 million  dollars that will be paid in annual installments of $ 5 million. Tuvalu is even honoring the domain sale with its own stamp. Tuvalu's government used the money to procure IT infrastructure for the most important government institutions and paid the entry fee for the United Nations .

Geographical areas

Countries or the companies that market their TLDs are also trying to create a market by using abbreviations that are intended to put the address in a context that was not originally given. One company is marketing the .la ( Laos ) domain as a domain for Los Angeles .


.de : The German ccTLD is also used by providers from Delaware .

Federal states

.by ( Belarus ): This ccTLD can be used for pages with a Bavarian background and some companies in Bavaria . The state government uses for tourism purposes.

.sh ( St. Helena ): Somecompanies basedin Schleswig-Holstein use this ccTLD.

.mv ( Maldives ): Somecompanies basedin Mecklenburg-Western Pomerania use this ccTLD.

Counties and independent cities

The following list is only to be understood as a selection.

.ac ( Ascension ): License plate AC from Aachen

.hm ( Heard and McDonald Islands ): license plate HM of the district of Hameln-Pyrmont

.hn ( Honduras ): Heilbronn license plate HN

.kn ( St. Kitts and Nevis ): license plate KN of Konstanz

.la ( Laos ): Landshut's LA license plate

.li ( Liechtenstein ): LI district license plate for Lindau (Lake Constance) .

.mg ( Madagascar ): MG license plate from Mönchengladbach

.ms ( Montserrat ): MS license plate from Münster , North Rhine-Westphalia

.mw ( Malawi ): Vehicle registration number MW from Mittweida

.ro ( Romania ): RO license plate of the independent city of Rosenheim

.rs ( Serbia ): RS license plate for the independent city of Remscheid


In Switzerland, where the cantons are always abbreviated with two letters, ccTLDs are sometimes used to market offers relating to a canton. For example:

.ag ( Antigua and Barbuda ): Canton of Aargau

.be ( Belgium ): Canton of Bern

.bs ( Bahamas ): Canton of Basel-Stadt

.gl ( Greenland ): Canton of Glarus

.gr ( Greece ): Canton of Graubünden

.lu ( Luxembourg ): Canton of Lucerne

.sg ( Singapore ): Canton of St. Gallen

.sh ( St. Helena ): Canton of Schaffhausen


.md ( Republic of Moldova ): Mödling districtin Lower Austria

.st ( São Tomé and Príncipe ): State of Styria



.as ( American Samoa ): Autonomous Community of Asturias

More abbreviations

.ag ( Antigua and Barbuda ): The ccTLD of this island state is advertised by the operator in addition to its intended use specifically for companies in German-speaking countries in order to clarify their legal form of a stock corporation (AG).

.dj ( Djibouti ): some DJs now use themas a domain for their internet presence.

.io ( British Indian Ocean Territory ): The abbreviation for "input / output" ( input and output ) commonly associated with IT generally used or technology.

.kg ( Kyrgyzstan ): was offered to German and Austrian limited partnerships (abbreviation KG) as a domainfor a while.

.sl ( Sierra Leone ): This ccTLD has been marketed since 2008 and was mainly used by fans of the virtual world Second Life .

.tc ( Turks and Caicos Islands ): In Turkey, oftenmisusedfor Türkiye Cumhuriyeti (Turkish Republic, actually .tr ).

.tk ( Tokelau ): misappropriated by telecommunications companies ("TK companies").

.ws ( Samoa ): can be marketed as a "website", although such an abbreviation is uncommon.

Other examples

All domains (as of 2017)

TLDs are listed here that have no meaning as an abbreviation (like all of the above), but are used for other reasons.

.it ( Italy ): In English it means it , with it domains like , or the like can be generated.

.me ( Montenegro ): It can be used to create meaningful domains, such as. B .: , etc. However, such domains cannot be registered by the interested party, but are auctioned after the open registration.

.nu ( Niue ): The use of this domain for the pages of the Dresden culture magazine , whichalludes to the nu for "yes" usedin the local Dresden region,is unusual. The domain has a similar meaning in Sweden , Denmark and the Netherlands , since nu means "now"in Swedish , Danish and Dutch , as well as in many English-speaking countries where it is a non-spelling variant of new "new". In addition, .se domains (Sweden) were previously not registered there for private individuals. French-language adult sites like to use this ending, as the word nu translates as naked .

.cc ( coconut islands ): is very popular because it can be registered by anyone and the whois system is minimalist. (Only the domain registrar is disclosed, which means that the domain operator remains virtually anonymous.)

In addition to the domains mentioned here, there are a large number of domains with imaginative names such as .creditcard .futbol and much more. More than 600 domains are listed in the picture. Which of these possible domains will actually be used is questionable.

Technical and administrative implementation

For each top-level domain there is a group of name servers that manage the entire namespace of this domain (usually by means of delegations to other servers). These domain-specific name servers can be reached via the root name servers. There is also a central database that contains administrative information on all second-level domains located below this TLD, such as the name and address of the respective domain owner. This database can be accessed via the Whois service.

For the operation of the server and the database, ICANN commissions an organization for each domain, which is called the Domain Name Registry in Internet terminology . For the .com TLD, for example, this is VeriSign , for .de, DENIC . Such a registry is also responsible for assigning directly subordinate second-level domains (e.g. ). However, this task is often delegated to so-called registrars (see also: Domain registration ).

For every TLD there are guidelines that regulate the allocation of second-level domains. These are available on the websites of the respective registries. For some TLDs there are IDN language tables in which all special characters are listed that may be used when assigning subdomains. For example, German umlauts are permitted for .biz and .org. These tables are administered by IANA and can be viewed on the registries' websites.

Alternative root DNS

There are also organizations on the Internet that operate alternative name servers through which further TLDs are available in addition to the quasi-official TLDs controlled by ICANN . A decisive disadvantage is that such addresses cannot be reached by conventional Internet users. They are also ignored by search engines like Google . Another disadvantage is that the namespaces of two operators can collide, especially if further top level domains are introduced later.

The OpenNIC project tries to merge the alternative systems, but regards the ICANN TLDs as priority and accepts neither conflicting nor private namespaces. The own TLDs are .glue , .indy , .geek , .null , .oss and .parody .

statistical data

In the second quarter of 2018, the total number of registered domains was over 329 million.

The most frequently registered TLDs worldwide (as of October 2018):

TLD Registry Domains States
.com VeriSign 137.612.980
.tk Teletok 21,177,784 TokelauTokelau Tokelau
.de DENIC 14,553,237 GermanyGermany Germany
.net VeriSign 13,969,042
.cn CNNIC 10,890,519 China People's RepublicPeople's Republic of China People's Republic of China
.org PIR 10,384,821
.uk Nominet 10,378,161 United KingdomUnited Kingdom United Kingdom
.info Afilias 5,410,612
.nl SIDN 5,073,833 NetherlandsNetherlands Netherlands
.ru CC for TLD RU 4,921,743 RussiaRussia Russia
.eu EURid 3,656,069 European UnionEuropean Union European Union
.Top ICANN 3,365,438
.br 3,342,309 BrazilBrazil Brazil
.fr afnic 3,221,025 FranceFrance France
.au auDA 2,859,330 AustraliaAustralia Australia
.it IIT-CNR 2,799,023 ItalyItaly Italy
.approx CIRA 2,631,525 CanadaCanada Canada
.ga RIPE Network Coordination Center 2,353,985 GabonGabon Gabon
.pl NASK 2,321,213 PolandPoland Poland
.co NEUSTAR 2,256,536 ColombiaColombia Colombia
.biz neustar Domain Registry 2.250.208
.cf SOCATEL 2,238,368 Central African RepublicCentral African Republic Central African Republic

TLDs from states with German as the official language:

TLD Registry Domains States
.de DENIC 14,553,237 GermanyGermany Germany
.ch SWITCH 1,855,535 SwitzerlandSwitzerland Switzerland
.be DNS Belgium 1,479,189 BelgiumBelgium Belgium
.at 1,264,742 AustriaAustria Austria
.lu 82,707 LuxembourgLuxembourg Luxembourg
.li SWITCH 51,058 LiechtensteinLiechtenstein Liechtenstein

See also

Web links

Wiktionary: top-level domain  - explanations of meanings, word origins, synonyms, translations
Wiktionary: Domain  - explanations of meanings, word origins, synonyms, translations
Wiktionary: Domain extension  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. DENIC eG: Domainmarkt International
  2. Statista - Evaluations Domains Q1 2017 Accessed on February 27, 2013.
  3. a b c Terry Manderson (ICANN): TLD DNSSEC Report , November 11, 2012. Accessed November 11, 2012.
  4. ^ ICANN - Archives - ICANN Montreal Meeting Topic: Review of ICANN's Geographic Regions. In: July 15, 2000, accessed March 5, 2020 .
  5. Home - dotMobi. Internet made mobile. Everywhere, every device. In: Retrieved March 2, 2015 .
  6. ICM Registry - .XXX Sponsored Top Level Domain. (No longer available online.) In: Archived from the original on December 31, 2016 ; accessed on March 2, 2015 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot /
  7. Monika Ermert: Green light for new Internet address zones - heise online. In: June 26, 2008, accessed March 2, 2015 .
  8. Florian Hitzelberger: nTLDs - June 13, 2012 is »reveal day«! In: June 13, 2012, accessed March 2, 2015 .
  9. Reveal Day 13 June 2012 - New gTLD Applied-For Strings ( Memento from June 15, 2012 in the Internet Archive ), ICANN. Retrieved June 14, 2012.
  10. Multicast DNS. In: IETF . February 2012, accessed March 5, 2020 .
  11. IANA ccTLD database on Internet Assigned Numbers Authority. In: Retrieved March 2, 2015 .
  12. ISO 3161 FAQ: What is the ISO 3166-1 code for the European Union? ( Memento from June 6, 2011 in the Internet Archive )
  13. ^ Robert Scheck - Internet - Top-Level-Domain .DD. In: Retrieved March 2, 2015 .
  14. ^ IAB to ICANN: IAB input related to the .cs code in ISO 3166, September 24, 2003 - Internet Architecture Board. In: December 16, 2011, accessed March 5, 2020 .
  15. ^ IANA - Report on the Revocation of the .UM Top-Level Domain. In: January 16, 2007, accessed March 5, 2020 .
  16. Rts, Radio Televizija Srbije, Radio Television O: Збогом yu домену. In: March 1, 2015, accessed March 2, 2015 (ci).
  17. Internet extension .AN as of July 31st uit de lucht - Curacao. In: Curacao. July 7, 2015, accessed March 13, 2016 (Dutch).
  18. Florian Hitzelberger: IANA - three new ccTLDs born! In: domain-right. January 25, 2011, accessed March 13, 2016 .
  19. Domain names registration in SU. In: Retrieved March 2, 2015 .
  20. 6 Déc 2011 - Overture to l'Europe du .fr et des autres TLDs opérés par l'AFNIC. Retrieved February 6, 2019 (French).
  21. Allocation of one- and two-digit domains as well as domains consisting only of digits on
  22. Marc Störing: Court: Denic has to assign domain with two letters. In: June 18, 2008, accessed March 2, 2015 .
  23. ^ Nominet : Introducing Second Level Domain Names . Retrieved January 25, 2015.
  24. ↑ Allocation guidelines (Spanish) ( Memento from September 23, 2015 in the Internet Archive ) (PDF; 76 kB)
  25. ↑ A complete listing of the correspondence between TLD and German license plates can be found on the private website .
  26. for example for the University of Konstanz .
  27. for example for the “Landshuter Messe- u. Event GmbH ".
  28. .as is used very often by private individuals, companies, authorities and city administrations. Official websites of various municipalities can only be reached via a TLD that is not intended for use. Due to the small population of American Samoa in relation to Asturias, the majority of the owners of a domain with this extension come from Spain.
  29. ^ Judgment of the OLG Hamburg on the use of the TLD .ag in Germany
  30. THE DOMAIN NAME INDUSTRY BRIEF. (PDF) August 2018, accessed on October 8, 2018 .
  31. a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac Domain Count Statistics for TLDs. Retrieved October 8, 2018 .