What is a second-level domain (SLD)?

A second-level domain (SLD) is a component of a domain name that is located directly to the left of the top-level domain (TLD) extension. In the hierarchical structure of domain names, the second-level domain is the level immediately below the top-level domain.

Here's a breakdown of a typical domain name structure:

\[ \text{Subdomain} \, (\text{Optional}) \, . \, \text{Second-Level Domain} \, . \, \text{Top-Level Domain} \]

For example, in the domain name "example.com":

 "example" is the second-level domain.
 "com" is the top-level domain.

Second-level domains are often chosen to represent the primary identity, brand, or purpose of a website. They are the most recognizable and memorable part of a domain name and play a significant role in establishing a website's online presence and identity.

In some cases, domain names may have additional subdomains preceding the second-level domain. For example:

 "blog.example.com"
 "store.example.com"

In these examples, "blog" and "store" are subdomains, while "example" remains the second-level domain.

Second-level domains are subject to registration by domain registrants, who must adhere to the rules and policies established by the relevant domain registry for the specific TLD. The availability of specific second-level domain names may vary depending on factors such as the popularity of the TLD, registration restrictions, and the presence of competing registrations.