[WEBINAR] The New Normal: Dealing with the Reality of an Unsecure World

Third-Level Domain

Definition - What does Third-Level Domain mean?

A third-level domain is the next highest level following the second-level domain in domain name hierarchy. It is the segment that is found directly to the left of the second-level domain. The third-level domain is often called a "subdomain", and includes a third domain section to the URL.

In large organizations, every department or division may include a unique third-level domain that can act as a simple, yet effective, way of identifying that particular department.

Various third-level domain names are used to balance the load on sites with heavy traffic. At times, names like www1 or www2 are used for this objective.

Techopedia explains Third-Level Domain

For example, in, "www" is the third-level domain. The default or the most commonly used third-level domain is "www". The third-level domain is generally used to mention a certain server inside a company.

Domain names are made with a minimum of two levels, a top-level domain (TLD) and a second-level domain. TLD is the extension or suffix attached to the domain names. Only a small selection of predefined TLDs are available, including .com, .org, .net, .biz, etc.

A second-level domain refers to the part of a Uniform Resource Locator (URL) that specifies the precise administrative owner linked to an Internet Protocol (IP) address. The second-level domain name incorporates the TLD name as well. For example, in, ".com" is the TLD and "" is the second level domain.

Third-level domain names are not mandatory unless the user has a specific requirement. It is actually possible to own a fully functional domain name like "". All that is needed is two levels: the top level domain and the second-level domain name. However, the usage of third-level domain names can really add clarity to domain names, which makes them more intuitive.

Customized third-level domains are also used for specific purposes. For instance, if has a file transfer protocol (FTP) server to let users download files, its third-level domain name can be termed ftp and the full domain name would then be Similarly, the domain names such as and can be employed to differentiate the support department and member department of respectively. This will help direct the Web traffic accordingly.

Techopedia Deals

Connect with us

Techopedia on Linkedin
Techopedia on Linkedin
"Techopedia" on Twitter

Sign up for Techopedia's Free Newsletter!

Email Newsletter

Join thousands of others with our weekly newsletter

Free Whitepaper: The Path to Hybrid Cloud
Free Whitepaper: The Path to Hybrid Cloud:
The Path to Hybrid Cloud: Intelligent Bursting To Amazon Web Services & Microsoft Azure
Free E-Book: Public Cloud Guide
Free E-Book: Public Cloud Guide:
This white paper is for leaders of Operations, Engineering, or Infrastructure teams who are creating or executing an IT roadmap.
Free Tool: Virtual Health Monitor
Free Tool: Virtual Health Monitor:
Virtual Health Monitor is a free virtualization monitoring and reporting tool for VMware, Hyper-V, RHEV, and XenServer environments.
Free 30 Day Trial – Turbonomic
Free 30 Day Trial – Turbonomic:
Turbonomic delivers an autonomic platform where virtual and cloud environments self-manage in real-time to assure application performance.