Domain name Levels Question

Started by ACKET, Aug 15, 2022, 08:36 AM

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ACKETTopic starter

Can you explain the meaning behind the terms first-level, second-level, and third-level domain? As an example, consider the domain In this case, "bar" and "foo" are both domains.

It's interesting to note that the website is made up of four domains that each belong to distinct organizations.


To clarify any confusion about domain names, here are some definitions from

A domain is a specific branch of the hierarchical domain name system on the Internet, which is identified by a unique domain name.

The domain name is the symbolic name assigned to the domain and must be unique within the same domain. The full name of a domain is made up of all the domains it belongs to, separated by dots. For example, refers to the third-level domain "en," within the second-level domain "wikipedia," under the "org" top-level domain, which is part of the root domain. Domain names are used to address internet nodes and network resources like websites or email servers in a person-friendly format.

A domain zone is a group of domain names at a certain level, included within a specific domain, such as the zone which includes all third-level domains in that domain. The term "domain zone" is mainly used in technical contexts related to DNS servers such as zone maintenance, zone delegation, and zone transfer.

For those who may not be aware, there exists a "." or root domain as well, as you can read about here:

Additionally, you can find information about top-level domains at


In simpler terms, the main domain name of a website, such as, is considered the primary identifier or name for the site. This is known as a second-level domain, as the first-level domain is the domain zone (.com).

However, it's possible to add additional levels to the domain name. Third-level and higher subdomains are often used for alternate language versions of the site, such as, or for separate projects affiliated with the company, like These subdomains may appear to be separate sites, but are still indirectly linked to the main site.

Gregor Bishop

Although it may seem complicated, the concept of domain levels is actually quite simple. In the past, IP addresses were used instead of domains, such as for However, to make it easier, first-level domains were created, which look like with .name being the name of the site. There are approximately 1000 first-level domains, which are thematic or geographical and also referred to as generic or top-level domains. Examples of these are .com and .org.

Domain levels beyond the first level are determined by the number of words used after http(s). For instance, a fifth-level domain would be, while is considered a fourth-level domain, as per this formula. Although there are up to six levels of domains, the number of levels can vary according to the website.


In the context of domain names, the terms first-level, second-level, and third-level domains refer to different levels of hierarchy within a fully qualified domain name (FQDN).

In your example, "," each segment separated by a dot represents a different level of domain. Let's break it down:

1. Top-Level Domain (TLD): This is the rightmost portion of the domain name. In this case, "com" is the TLD. Common examples include .com, .org, .net, and country-specific TLDs like .us or .uk.

2. Second-Level Domain (SLD): It is the domain name immediately to the left of the TLD. In the given example, "website" is the SLD.

3. Third-Level Domain: It is the next domain portion to the left of the SLD. In this case, "foo" is the third-level domain.

4. Fourth-Level Domain: Finally, "bar" represents the fourth-level domain in your example.

hierarchy of domain names:

- Top-Level Domain (TLD): This is the highest level in the domain name system. TLDs are typically divided into two categories: generic top-level domains (gTLDs) and country code top-level domains (ccTLDs). Examples of gTLDs include .com, .org, .net, and .edu, while examples of ccTLDs include .us, .uk, .ca, and .jp.

- Second-Level Domain (SLD): This is the domain name directly to the left of the TLD. It is often chosen by the website owner and represents their brand, organization, or purpose. In the example "," "website" is the SLD.

- Third-Level Domain: The domain name to the left of the SLD is known as the third-level domain. It can be used to further specify a particular section or department within an organization or to create subdomains for different services or branches. In the given example, "foo" is the third-level domain.

- Fourth-Level Domain: Some domain names may have additional levels beyond the third level, such as "bar" in the example "" These additional levels allow for even more specific categorization or separation within the domain structure.

- Subdomain: A subdomain is a domain that is part of a larger domain. It precedes the main domain name and is separated by a dot. For example, in the domain "," "blog" is a subdomain of "" Subdomains are often used to categorize or differentiate different sections or services of a website.

- Root Domain: The root domain is the highest level of a domain hierarchy and does not have any additional subdomains preceding it. It represents the main domain name of a website. For example, in the domain "," "com" is the top-level domain (TLD), and "example" is the root domain.

- Fully Qualified Domain Name (FQDN): An FQDN is a complete domain name that specifies the exact location of a resource on the internet. It consists of all the levels of the domain hierarchy, including the hostname and the TLD. In the example "," the FQDN represents a specific website or resource hosted at that domain.

- Subdirectories: In addition to subdomains, websites can also use subdirectories to organize content. A subdirectory appears after the root domain in the URL and is separated by a forward slash (/). For example, in the URL "," "blog" is a subdirectory of the website.

- Domain Registrars: Domain names are registered through domain registrars, which are companies authorized by domain name registries to manage the registration process. Popular domain registrars include GoDaddy, Namecheap, and Google Domains. Registrars allow individuals and organizations to reserve and manage domain names for a specified period by paying a registration fee.

- DNS (Domain Name System): The Domain Name System is a decentralized naming system that translates domain names into IP addresses. When you type a domain name into a web browser, the DNS servers look up the IP address associated with that domain name and then connect you to the correct website. DNS ensures that human-readable domain names can be easily understood and accessed by computers on the internet.

- WHOIS: WHOIS is a protocol used to query databases that contain information about registered domain names. It provides information such as the registrant's name, contact details, registration date, expiration date, and name servers associated with a particular domain name. WHOIS allows users to verify ownership and contact the appropriate party for a specific domain.

- Domain Name System (DNS) Records: DNS records are used to provide additional information about a domain name. They define how the domain name should be resolved and what services are associated with it. Common DNS records include A records (which map a domain to an IP address), CNAME records (which create aliases for a domain), MX records (which specify mail servers for a domain), and TXT records (which can hold arbitrary text information).

- Internationalized Domain Names (IDNs): IDNs allow domain names to be registered using non-ASCII characters. This enables domain names to be written in different scripts and languages, making the web more accessible and inclusive. For example, it allows domain names to be written in Cyrillic, Arabic, Chinese, and other non-Latin scripts.

- Domain Privacy: When registering a domain, you have the option to enable domain privacy or WHOIS privacy. This hides your personal contact information from being publicly displayed in the WHOIS database. Instead, a proxy service will display their information, providing a layer of privacy and protection against spam or unwanted solicitations.

- Domain Name Transfer: Domain names can be transferred between domain registrars. This allows individuals or organizations to switch their domain management services without losing ownership of the domain. Domain transfers involve following specific procedures and usually require an authorization code or EPP key to initiate the process.

- Domain Expiration: Domain names are typically registered for a specific period, ranging from one to ten years. It's important to renew the domain registration before it expires to avoid losing ownership. If a domain expires and is not renewed, it may become available for others to register.