Second-Level Domain (SLD)

May 20, 2023

A Second-Level Domain (SLD) is a component of a fully-qualified domain name (FQDN) that sits immediately to the left of the top-level domain (TLD). For example, in, the example portion of the URL is the second-level domain.

Purpose and Usage

The purpose of an SLD is to provide a unique identifier for a website. The SLD is the part of the URL that is registered with a domain registrar and is used to differentiate one website from another. This is important because there can be multiple websites with the same name or brand, but each website must have a unique domain name.

In practice, SLDs are used to create memorable and unique web addresses for websites. They are often tied to a brand or company name, making them easily recognizable and memorable for users. For example, is a memorable web address that is associated with the Apple brand.

In addition to branding and user recognition, SLDs can also have an impact on search engine optimization (SEO). The words used in an SLD can help search engines understand the content of a website and improve its ranking in search results.


It’s important to differentiate between SLDs and TLDs. A TLD is the highest level of the domain name system (DNS) hierarchy and is used to indicate the type of organization or geographical location of a website. Examples of TLDs include .com, .org, and .edu.

While TLDs are used to differentiate between types of websites, SLDs are used to differentiate between individual websites within those categories. For example, while and both have the same TLD, they have different SLDs that differentiate them as separate websites.

Creating an SLD

To create an SLD, a website owner must first register a domain name with a domain registrar. The domain name must be unique and cannot be in use by another website.

Once the domain name is registered, the website owner can choose the SLD portion of the URL. This is typically the brand or company name, but can also be a descriptive term related to the website’s content.

When choosing an SLD, website owners should consider the following factors:

  • Branding: The SLD should be memorable and easily recognizable as part of the website’s brand.
  • Search Engine Optimization: The words used in the SLD can impact the website’s ranking in search engine results.
  • Length: Shorter SLDs are typically easier to remember and type.

SLDs in Practice

SLDs are used in a variety of contexts on the web. Some common examples include:

  • Business Websites: Many businesses use their company name as the SLD for their website. For example, and both use the company name as the SLD.
  • Blogs: Blogs often use descriptive terms related to the content of the blog as the SLD. For example, and both use descriptive terms related to the content of the website.
  • Personal Websites: Personal websites often use the individual’s name as the SLD. For example, and both use the individual’s name as the SLD.