Domains From the Top Down
Every website that you visit has a Uniform Resource Locator (URL)—the string that you type into the location bar or address bar at the top of your browser window in order to access the site. The URL includes a variety of information, including the registered domain name that is specific to the site, and always ends with the top-level domain (TLD) which is the first level of division on the Internet, grouping websites into categories. The same TLD will end any e-mail address associated with the website as well.
There are three distinct types of TLDs:
- Country code TLDs (cTLDs) are domain names that specify countries or dependent territories, usually matching the ISO 3166 codes for the countries, with a few exceptions.
- Generic TLDs (gTLDs) are domain names that represent classes or categories of organizations. This is the type that is usually under consideration when a person sets up a business or personal website.
- Infrastructure TLDs (iTLDs) are for the Internet infrastructure, as you might imagine. The only functional one currently is .arpa, which stands for “Address and Routing Parameter Area” and is not something that someone buying or selling domain names or setting up a business or personal website has to be concerned about.
TLDs are managed by the Internet Corporation for Assigned Names and Numbers, popularly known as the ICANN. Control of each TLD is delegated by the ICANN to a domain name registry.
Choices and More Choices
The top-level domains available today include some that date back to 1985 when the first set were created, and others that are new. For practical purposes, it is more useful to categorize them by whether they are restricted (which may mean that they are sponsored) or unrestricted (which usually means unsponsored). Further, sponsored TLDs (sometimes referred to as sTLDs) operate under a sponsor that represents the particular community for which the TLD is or particular interest, while unsponsored TLDs operate under the aegis of the ICANN acting on behalf of the global Internet community.
| gTLD | Specified Use, If Restricted | Sponsored? | Restricted? |
| .aero | Air transport industry | yes | yes |
| .asia | Companies, individuals, and organizations in the Asia/Pacific region | yes | yes |
| .biz | Businesses using the Internet for commerce | no | yes |
| .cat | Catalan culture and language | yes | yes |
| .com | no | no | |
| .coop | Cooperatives | yes | yes |
| .edu | Post-secondary educational institutions | no | yes |
| .gov | US Federal, state, and local government | no | yes |
| .info | no | no | |
| .int | International organizations established by treaty | no | yes |
| .jobs | Employment-related sites | yes | yes |
| .mil | US military and the Department of Defense | no | yes |
| .mobi | Sites delivering content to mobile devices | yes | yes |
| .museum | Museums | yes | yes |
| .name | Limited to one’s own personal name (legal or customary or pseudonym) and fictional characters that one holds trademark or service mark for. | no | no |
| .net | no | no | |
| .org | no | no | |
| .pro | Legal, medical, and accountancy professionals and organizations | no | yes |
| .tel | Internet-communication services | yes | yes |
| .travel | Travel industry | yes | yes |
The TLD .xxx has been rejected by ICANN, and .post—designed for postal agencies—is still under consideration.
