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Top-level domain (TLD) refers to the last segment of a domain name, or the part that follows immediately after the "dot" symbol.
For example, in the internet address: https://www.google.com, the “.com” portion is the TLD.
TLDs are mainly classified into two categories: generic TLDs and country-specific TLDs.
Examples of some of the popular TLDs include:
The Internet Corporation for Assigned Names and Numbers (ICANN), is the entity that coordinates domains and IP addresses for the internet.
Historically, TLDs represented the purpose and type of domain or the geographical area from which it originated. ICANN has generally been very strict about opening up new TLDs, but in 2010, it decided to allow the creation of numerous new generic TLDs as well as TLDs for company-specific trademarks.
Top-level domains are also known as domain suffixes.
ARPANET created TLDs to allow humans to ease the process of memorizing IP addresses. Instead of using a series of digits for each computer, the domain name system was established to organize addresses in a more user-friendly way.
In 1971, the first email was developed and sent using an “@” symbol. The "address" after the @ was not the domain but the actual computer it was sending to. In the early 1980s, when the earliest domains started being developed, the first TLDs such as .org and .com saw the light.
A top-level domain recognizes a certain element regarding the associated website, such as its objective (business, government, education), its owner, or the geographical area from which it originated.
Each TLD includes an independent registry controlled by a specific organization, which is managed under the guidance of the Internet Corporation for Assigned Names and Numbers (ICANN).
ICANN recognizes the following types of TLDs:
These are the most popular types of TDLs. Some examples include ".edu" for educational sites and ."com" for commercial sites. These types of TLDs are available for registration.
Every ccTLD recognizes a specific country and is generally two letters long. For example, the ccTLD for Australia is ".au".
These TLDs are supervised by private organizations.
There is only one TLD in this category, which is ".arpa". The Internet Assigned Numbers Authority controls this TLD for the Internet Engineering Task Force (IETF).
In earlier times, the purpose of each TLD was specific, such as .com which was used only for commercial websites. Eventually, as the Internet kept growing and evolving, this restriction was abandoned, and now there’s almost no distinction between most TLDs.
However, some TLDs are reserved for some unique purposes even today, such as gTLDs that are assigned for educational institutions (.edu) and those assigned for government and the military (.gov and .mil).
Some of the TLDs and their original 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.
Currently, some TLDs are more difficult to get compared to easy ones such as .com. Because of this, many organizations register multiple TLDs and redirect them as necessary to the main one used for their principal web resource.