What is a top-level domain?
A top-level domain (TLD) is the right-most part of a domain name. Some of the most common TLDs are .com, .net., and .gov.
What the different types of TLDs?
- Generic TLD (gTLD): Generic TLDs are controlled by IANA, the Internet Assigned Numbers Authority. These TLDs are called generic for historic reasons, but they are some of the most commonly found such as .com. and .net. These are more traditional gTLDs but
- Country-code TLDs (ccTLD): Maintained by IANA, these TLDs apply to countries. For example, in menandmice.is the .is is for Iceland. These TLDs are subject to different policies than generic TLDs.
- Sponsored TLDs: Maintained by IANA, these TLDs represent specific communities such as geographic locations, ethnicities, and professions.
- Unsponsored TLDs: Maintained by IANA, but unlike sponsored TLDs these have no specific owner and our subject to more governance from ICANN (Internet Corporation for Assigned Names and Numbers)
- Infrastructure TLDs: Used exclusively for Internet infrastructure spaces. Currently only .arpa is an infrastructure TLD
- Reserved TLDs: IANA reserved a small amount of TLDs for testing DNS related code and experimentation. Examples are .test and .example.
- Internationalized country code top-level domains (IDN ccTLD): similar to the ccTLD except these are written in a country’s common language and language native script
What is a top-level domain example?
In the hierarchy of the domain name system (DNS) the top-level domain is just that, at the top. These domains are generally maintained by IANA, a part of ICANN. You can think of each TLD as having its own tree or registry. For example, menandmice.com will not take you to the same place as menandmice.net because they are in two totally different hierarchies.
The TLD is a part of the domain name. The domain name is part of a URL, sometimes referred to as a web address, as shown in the image at the top of this article. There is a difference when referring to TLDs on the public Internet, as opposed to if someone were to name their internal domain example.com. Internally this name would not be controlled by associations such as ICANN or IANA unless these domains were to be registered with ICANN and used publicly as well.
When a client tries to access a particular URL, it will first check with the DNS server that it’s been assigned to check with. If it doesn’t find the DNS entry there, it will go to the next DNS server, sometimes the secondary DNS server. If it’s not found there, it will go to the next until it eventually finds the information with the top-level DNS server. This information will then be cached for a period of time so that it’s easier to find.