What is a Top-Level Domain
A top-level domain (TLD) is the last segment of the domain name. The TLD is the letters immediately following the final dot in an Internet address.
A TLD identifies something about the website associated with it, such as its purpose, the organization that owns it or the geographical area where it originates. Each TLD has a separate registry managed by a designated organization under the direction of the Internet Corporation for Assigned Names and Numbers (ICANN).
In our Internet address, http://student.unilearning.net/: .net is the top-level domain name; unilearning.net is the second-level domain name; and student is a subdomain name. All together, these constitute a fully-qualified domain name (FQDN); the addition of HTTP:// makes an FQDN a complete URL.
ICANN identifies the following categories of TLDs:
- Country-code top-level domains (ccTLD) — Each ccTLD identifies a particular country and is two letters long. The ccTLD for the United States, for example, is .us
- Infrastructure top-level domain — There is only one TLD in this group, ARPA (Address and Routing Parameter Area). The Internet Assigned Numbers Authority (IANA) manages this TLD for the Internet Engineering Task Force(IETF).
- Sponsored top-level domains (sTLD): These are overseen by private organizations.
- Generic top-level domains (gTLD) — These are the most common and familiar TLDs. Examples include “com” for “commercial” and “edu” for “educational.” Most gTLDs are open for registration by anyone, but there is also a subgroup that is more strictly controlled.
Some of the TLDs and their explanations are as follows:
- .com – Commercial businesses
- .org – Organizations (generally charitable)
- .net – Network organizations
- .gov – U.S. government agencies
- .mil – Military
- .edu – Educational facilities like universities
- .th – Thailand
- .ca – Canada
- .au – Australia
According to the IETF, there are four top-level domain names that are reserved, and are not used in production networks inside the worldwide domain name system:
- .example – Only available to use in examples
- .invalid – Only available to use in invalid domain names
- .localhost – Only available to use in local computers
- .test – Only available to use in tests.