Domain Name and Domain Extensions

The most common types of domain names are hostnames that provide more memorable names to stand in for numeric IP addresses. They allow for any service to move to a different location in the topology of the Internet (or an intranet), which would then have a different IP address.

By allowing the use of unique alphabetical addresses instead of numeric ones, domain names allow Internet users to more easily find and communicate with web sites and other server-based services. The flexibility of the domain name system allows multiple IP addresses to be assigned to a single domain name, or multiple domain names to be assigned to a single IP address. This means that one server may have multiple roles (such as hosting multiple independent websites), or that one role can be spread among many servers. One IP address can also be assigned to several servers, as used in anycast and hijacked IP space.

Hostnames are restricted to the ASCII letters a through z (case-insensitive), the digits 0 through 9, and the hyphen, with some other restrictions. Registrars restrict the domains to valid hostnames, because they otherwise would be useless. The Internationalized domain name (IDN) system has been developed to bypass the restrictions on character allowances in hostnames, making it easier for users of non-English alphabets to use the Internet. The underscore character is frequently used to ensure that a domain name is not recognized as a hostname, as with the use of SRV records, for example, although some older systems such as NetBIOS did allow it. Due to confusion and other reasons, domain names with underscores in them are sometimes used where hostnames are required.

Domain names are often referred to simply as domains and domain name registrants are frequently referred to as domain owners, although domain names, technically, are leased from a registrar.

The list of Generic Top Level Domain Name (gTLD) Extensions

• .aero - for the air transport industry
• .asia - for companies. organisations and individuals in the Asia-Pacific region
• .biz - for business use
• .cat - for Catalan language/culture
• .com - for commercial organizations, but unrestricted
• .coop - for cooperatives
• .edu - for post-secondary educational establishments
• .gov - for government entities within the United States at the federal, state, and local levels
• .info - for informational sites, but unrestricted
• .int - for international organizations established by treaty
• .jobs - for employment-related sites
• .mil - for the U.S. military
• .mobi - for sites catering to mobile devices
• .museum - for museums
• .name - for families and individuals
• .net - originally for network infrastructures, now unrestricted
• .org - originally for organizations not clearly falling within the other gTLDs, now unrestricted
• .pro - for certain professions
• .tel - for services involving connections between the telephone network and the Internet
• .travel - for travel agents, airlines, hoteliers, tourism bureaus, etc.

The following gTLDs are in the process of being approved, and may be added to the root nameservers in the near future:

• .post - for postal services
• .geo - for geographically related sites
• .cym - for Welsh language/culture

Country code top-level domain (ccTLD) Extesions

A country code top-level domain (ccTLD) is an Internet top-level domain generally used or reserved for a country or a dependent territory.

A

• ac – Ascension Island


• ad – Andorra


• ae – United Arab Emirates


• af – Afghanistan


• ag – Antigua and Barbuda


• ai – Anguilla


• al – Albania


• am – Armenia


• an – Netherlands Antilles


• ao – Angola


• aq – Antarctica


• ar – Argentina


• as – American Samoa


• at – Austria


• au – Australia


• aw – Aruba


• ax – Åland Islands


• az – Azerbaijan

B

• ba – Bosnia and Herzegovina


• bb – Barbados


• bd – Bangladesh


• be – Belgium


• bf – Burkina Faso


• bg – Bulgaria


• bh – Bahrain


• bi – Burundi


• bj – Benin


• bm – Bermuda


• bn – Brunei


• bo – Bolivia


• br – Brazil


• bs – Bahamas


• bt – Bhutan


• bv – Bouvet Island (not in use; no registrations)


• bw – Botswana


• by – Belarus


• bz – Belize

C

• ca – Canada


• cc – Cocos (Keeling) Islands


• cd – Democratic Republic of the Congo (formerly
• zr – Zaire)


• cf – Central African Republic


• cg – Republic of the Congo


• ch – Switzerland


• ci – Côte d'Ivoire (Ivory Coast)


• ck – Cook Islands


• cl – Chile


• cm – Cameroon


• cn – People's Republic of China


• co – Colombia


• cr – Costa Rica


• cu – Cuba


• cv – Cape Verde


• cx – Christmas Island


• cy – Cyprus


• cz – Czech Republic

D

• de – Germany


• dj – Djibouti


• dk – Denmark


• dm – Dominica


• do – Dominican Republic


• dz – Algeria

E

• ec – Ecuador


• ee – Estonia


• eg – Egypt


• eh – Western Sahara (not assigned; no DNS)


• er – Eritrea


• es – Spain


• et – Ethiopia


• eu – European Union (code "exceptionally reserved" by ISO 3166-1)

F

• fi – Finland


• fj – Fiji


• fk – Falkland Islands


• fm – Federated States of Micronesia


• fo – Faroe Islands


• fr – France

G

• ga – Gabon


• gb – United Kingdom (Reserved domain by IANA; deprecated – see
• uk)


• gd – Grenada


• ge – Georgia


• gf – French Guiana


• gg – Guernsey


• gh – Ghana


• gi – Gibraltar


• gl – Greenland


• gm – Gambia


• gn – Guinea


• gp – Guadeloupe


• gq – Equatorial Guinea


• gr – Greece


• gs – South Georgia and the South Sandwich Islands


• gt – Guatemala


• gu – Guam


• gw – Guinea-Bissau


• gy – Guyana

H

• hk – Hong Kong


• hm – Heard Island and McDonald Islands


• hn – Honduras


• hr – Croatia


• ht – Haiti


• hu – Hungary

I

• id – Indonesia


• ie – Ireland


• il – Israel


• im – Isle of Man


• in – India


• io – British Indian Ocean Territory


• iq – Iraq


• ir – Iran


• is – Iceland


• it – Italy

J

• je – Jersey


• jm – Jamaica


• jo – Jordan


• jp – Japan

K

• ke – Kenya


• kg – Kyrgyzstan


• kh – Cambodia


• ki – Kiribati


• km – Comoros


• kn – Saint Kitts and Nevis


• kp – North Korea


• kr – South Korea


• kw – Kuwait


• ky – Cayman Islands


• kz – Kazakhstan

L

• la – Laos


• lb – Lebanon


• lc – Saint Lucia


• li – Liechtenstein


• lk – Sri Lanka


• lr – Liberia


• ls – Lesotho


• lt – Lithuania


• lu – Luxembourg


• lv – Latvia


• ly – Libya

M

• ma – Morocco


• mc – Monaco


• md – Moldova


• me – Montenegro


• mg – Madagascar


• mh – Marshall Islands


• mk – Republic of Macedonia


• ml – Mali


• mm – Myanmar


• mn – Mongolia


• mo – Macau


• mp – Northern Mariana Islands


• mq – Martinique


• mr – Mauritania


• ms – Montserrat


• mt – Malta


• mu – Mauritius


• mv – Maldives


• mw – Malawi


• mx – Mexico


• my – Malaysia


• mz – Mozambique

N

• na – Namibia


• nc – New Caledonia


• ne – Niger


• nf – Norfolk Island


• ng – Nigeria


• ni – Nicaragua


• nl – Netherlands


• no – Norway


• np – Nepal


• nr – Nauru


• nu – Niue


• nz – New Zealand


• nc
• tr – North Cyprus

O

• om – Oman

P

• pa – Panama


• pe – Peru


• pf – French Polynesia


• pg – Papua New Guinea


• ph – Philippines


• pk – Pakistan


• pl – Poland


• pm – Saint Pierre and Miquelon


• pn – Pitcairn Islands


• pr – Puerto Rico


• ps – Palestinian Territory


• pt – Portugal


• pw – Palau


• py – Paraguay

Q

• qa – Qatar

R

• re – Réunion


• ro – Romania


• rs – Serbia


• ru – Russia


• rw – Rwanda

S

• sa – Saudi Arabia


• sb – Solomon Islands


• sc – Seychelles


• sd – Sudan


• se – Sweden


• sg – Singapore


• sh – Saint Helena


• si – Slovenia


• sj – Svalbard and Jan Mayen islands (not in use; no registrations)


• sk – Slovakia


• sl – Sierra Leone


• sm – San Marino


• sn – Senegal


• so – Somalia(down, still is delegated to Monolith [ml
• org] Philadelphia, an entity defunct since end-1998)


• sr – Suriname


• st – São Tomé and Príncipe


• su – Soviet Union (deprecated; being phased out; code "transitionally reserved" by ISO 3166-1)


• sv – El Salvador


• sy – Syria


• sz – Swaziland

T

• tc – Turks and Caicos Islands


• td – Chad


• tf – French Southern Territories


• tg – Togo


• th – Thailand


• tj – Tajikistan


• tk – Tokelau


• tl – East Timor (formerly
• tp)


• tm – Turkmenistan


• tn – Tunisia


• to – Tonga


• tp – East Timor (deprecated – use
• tl; code "transitionally reserved" by ISO 3166-1)


• tr – Turkey


• tt – Trinidad and Tobago


• tv – Tuvalu


• tw – Taiwan


• tz – Tanzania

U

• ua – Ukraine


• ug – Uganda


• uk – United Kingdom (code "exceptionally reserved" by ISO 3166-1) (see also
• gb)


• us – United States


• uy – Uruguay


• uz – Uzbekistan

V

• va – Vatican City


• vc – Saint Vincent and the Grenadines


• ve – Venezuela


• vg – British Virgin Islands


• vi – United States Virgin Islands


• vn – Vietnam


• vu – Vanuatu

W

• wf – Wallis and Futuna


• ws – Samoa (formerly Western Samoa)

Y

• ye – Yemen


• yt – Mayotte


• yu – Serbia and Montenegro

Z

• za – South Africa


• zm – Zambia


• zw – Zimbabwe