TLD
The letters displayed after the last dot of a domain name — such as .ca, .us, .org, .net and .com — are the TLD (top-level domain). It is therefore the most general component of the domain name.
![](https://kb.n0c.com/wp-content/uploads/2024/01/URL_EN-1-1024x481.jpg)
All domains are sub-domains of each other, except for the root (which is the beginning of the domains, so to speak). For example, abc.xyz.ca is a sub-domain of .xyz.ca, .xyz.ca is a sub-domain of .ca, and .ca is a sub-domain of the root.
There are three types of TLDs:
- Country code TLDs (ccTLDs).
- Generic TLDs.
- Special-Use TLDs.
Country code TLDs are associated with specific countries in that their subdomains share a common geographical characteristic.
Generic TLDs belong to ICANN. They are intended to host subdomains with a common non-geographic characteristic. Generic TLDs (or domains) can be “open” or “closed“. The open TLDs .net, .org, and .info are well known.
Special-Use TLDs have special features. One example is .arpa, which is used to solve infrastructure problems.
![](https://kb.n0c.com/wp-content/uploads/2022/03/image2021-3-31_8-6-37-1024x355.png)
Open and Closed Generic TLDs
Open TLDs have no restrictions. These TLDs have no specific fields, with a few exceptions.
For example :
- .app and .dev managed by Google must absolutely have the SSL (Secure Socket Layer) security protocol for them to be valid.
- .areo: you must be registered with an aeronautical order to register a domain name with this TLD.
- .travel: you need an agency number to register a domain name with this TLD.
Users who want to obtain subdomains in the category of closed (also called restricted) generic TLDs must comply with certain specific rules (or policies).