Fully Qualified Domain Names (FQDN): What They Are and Why They Matter

FQDN is the full URL of a specific server or a website. The FQDN usage is in some cases more reliable than the IP addresses.

To get a clearer understanding of what is FQDN, let’s use some examples for more visualization. For instance, the URL of the business website is “fdg.com”, then for the email service the FQDN is mail.fdg.com. This means that just by adding mail before the URL, you are getting a fully qualified domain name that relates to the service.

That is a more generic explanation of this topic, and now let’s dive into some details and a deeper understanding of FQDN.

Understanding Fully Qualified Domain Names (FQDN)

FQDN is a complete domain name of the host or certain server. The FQDN might be various depending on the situation. For instance, mail.skills.com and www.skills.com are both FQDN. In the situation when mail is a subdomain, this means that it relates to the mail server.

A fully qualified domain name is an entire path to the specific host, whereas the domain name and com part are only parts of this path.

Usually, the structure of FQDN consists of domain and host names. In the skills.com, “com” is the domain name, and “skills” is the hostname. However, that is not technically a FQDN, you will also need to add a sub-domain name (www) to have a full path.

If speaking about the sub-domain then usually they are www, but there are some exceptions from the regular cases. The host can have several sub-domains like in the previously discussed example mail.skills.com, mail is the sub-domain. It is also possible to change this sub-domain to “test” or other words depending on the necessity. That means test.skills.com is FQDN.  

How FQDN Differs from a URL

During some online communications, users sometimes use these terms interchangeably so there might be some confusion about the actual difference between URL and FQDN. The major distinction between the terms is that FQDN is a part of the URL.

Part of URLs that include HTTPS or HTTP are not related to the FQDN. With URL it is possible to specify file names, directory paths, and TCP ports. In the situations, when FQDN is used instead of URL to enter a specific website, then protocols HTTPS/HTTP are added automatically.

Examples to Illustrate FQDNs

FQDNs should have the following requirements in order to be related to this category:

-        Only letters, hyphens, and numbers can be used.

-        The entire FQDN can only consist of 255 characters max.

-        Every label should include a letter or number in the top position.

Now, let’s review an example of FQDN. www.skills.com consists of .com as top-level domain, skills – second-level domain, skills.com – domain name, and www.skills.com – FQDN.

The Purpose and Use Cases of an FQDN

Probably the most common user case for FQDN is the connection to the remote hosts. To connect to the server, you will definitely need to use FQDN, otherwise DNS can display an error. By filling in the full FQDN, you will surely have a successful connection specifically when the server is not in the local network.

Also, FQDN can be used during the migration process on the new server. It can be used instead of IP address and in such a way you can exclude communication troubles and outages. Moreover, FQDN can be helpful for brand promotion. SEO ranking can be also improved with the usage of FQDN.

Methods to Identify an FQDN

Depending on the used operating system identification of FQDN can slightly differ. Here, we will discuss the most standard approaches to the identification process.

Steps to Locate the FQDN on Windows 11

The process on Windows 11 is rather straightforward and doesn’t require specific technical skills. Here is the standard step-by-step process that will guide you through:

-         In the start menu, click on the settings.

-        Once in the settings, you should select “system”.

-        Then scroll down and press “about”.

-        In “about” there is plenty of information about the device and here you will find the domain name.

Another option is the usage of the command prompt:

-        In the start menu, open the terminal.

-        Type ipconfig/all so you will get all the necessary information about the IP configuration.

Steps to Locate the FQDN on macOS

For macOS users, the process is the following:

-        In the dock, you should select system settings.

-        Scroll to the Local hostname.

Another variant is via the terminal:

-        Open terminal.

-        Type hostname -f and you will receive FQDN.

What Are Partially Qualified Domain Names (PQDN)?

PQDN as its name suggests relates to the part of the domain name. Usually, a partially qualified domain name will be skills.com, but not mail.skills.com. Also, PQDN can be any part of FQDN, even just “www”.

Most of the reasons for the usage of PQDN are very technical and we will not overwhelm you with all the details. However, there is one practical usage for this term. In case, you are planning to share your FQDN in your blog or anywhere else, you should also account for specific PQDN for better accessibility.

For instance, in case your client types PGDN to access your resource, you should adjust settings accordingly so that missing parts will be added automatically to create FQDN. Converting is a crucial factor and you should know about it.