A domain is a unique Internet address for websites that is readable by humans. When working with domains and domain name system (DNS) management, it is helpful to understand what is a fully qualified domain name (FQDN). This article will help explain the concept of an FQDN and what makes up a domain name.
What is a Fully Qualified Domain Name (FQDN)?
A fully qualified domain name gives its precise location in the hierarchy of DNS records. It is the complete address for websites and other computers and entities accessing the Internet resolving to the root domain.
Using a Secure Sockets Layer (SSL) certificate helps secure your domain. An SSL certificate offers a secured connection via HTTPS, providing encryption and authentication for your web addresses.
Let’s deal with the parts of a domain, which will help us better understand what an FQDN is.
The Parts of a Domain
Computers interpret domains from right to left because the same domain name could be registered with multiple top-level domains (TLDs). Therefore, reading right-to-left allows DNS resolution to be accurate and efficient.
Let’s take a closer look at the hierarchical structure of a domain: the protocol, the subdomain, the domain name, and the TLD.
The top-level domain is the suffix at the end of the URL. Reading from right to left, the TLD is the first level of a domain’s hierarchy. A large number of TLDs exist like the ones below:
The second level of a domain’s hierarchy is the domain name. It is coupled with the TLD to form the root domain, which users register with their respective registrar and is the top-most page, or homepage, for your website. The domain name used on a specific TLD represents the unique location of any given website.
When accessing exampledomain.com, your browser explicitly asks the primary .com nameserver for the appropriate domain record for exampledomain, meaning the webpage https://www.exampledomain.com is returned in your browser instead of https://blog.exampledomain.com.
Subdomains are the third level of a domain’s hierarchy. They are added to the left of the domain name and separated by a period. The most common subdomain is www, but there are additional examples:
You can create any number of subdomains under the root domain, but the subdomain can also be blank:
- With a subdomain: https://www.exampledomain.com
- Without a subdomain: https://exampledomain.com
The protocol is the beginning portion of the URL (uniform resource locator), represented by either:
- Hypertext Transfer Protocol (HTTP).
- Hypertext Transfer Protocol Secure (HTTPS).
Your browser selects the appropriate protocol to use to request the website or resource.
Partially Qualified Domain Names (PQDN)
You may come across a term called a partially qualified domain name (PQDN). A PQDN is the root domain without the protocol or subdomain portions.
In the case of https://www.exampledomain.com, the PQDN is exampledomain.com as the domain name or the PQDN.
An FQDN is a complete domain that includes all the necessary components to resolve to an exact web address on the Internet. In addition to knowing what is an FQDN, we explored the elements of a domain and learned about partially qualified domain names.
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