A fully qualified domain name (FQDN) refers to the complete domain name of a specific computer or host on the Web. It has two parts—the hostname and the domain name.

Let’s say that your mail server’s FQDN is mymail[.]company[.]com. The hostname is mymail, whose host is company[.]com. Another example would be a web address like whoisxmlapi[.]com. Its FQDN is www[.]whoisxmlapi[.]com since it is hosted on www.

Other interesting terms…

Read More about an “FQDN

Let’s now take a closer look at the parts of an FQDN below.

Source: https://upload.wikimedia.org/wikipedia/commons/thumb/d/d2/DNS_schema.svg/700px-DNS_schema.svg.png

En[.]wikipedia[.]org is the FQDN of wikipedia[.]org, which means that the domain name wikipedia[.]org is hosted on en.

Why Do You Need to Know a Website’s FQDN?

An FQDN points to a unique address on the Web. Without an FQDN, users can’t access your website.

An FQDN is also essential in securing a site. You can’t install a Secure Sockets Layer (SSL) certificate, which is required to use the HTTPS protocol, without one.

You can also use an FQDN if you want your computer to become discoverable and accessible on the Internet. Offices do that to track all activities on the computers they own. A computer without an FQDN can’t be identified and remotely accessed on the Web.

Finally, an FQDN also helps you access domain-based services, such as File Transfer Protocol (FTP) and email.

How Do You Find Your Computer’s FQDN?

Finding your computer’s FQDN depends on the operating system (OS) it uses. For Windows, you can follow these steps:

  1. Launch the Control Panel. Type “control.exe” in the Run menu.
  2. Click the System menu.
  3. The System screen shows both your computer’s hostname (computer name) and FQDN (full computer name).
Source: https://www.ionos.com/digitalguide/fileadmin/DigitalGuide/Screenshots_2018/fqdn-anzeigen-windows-systemsteuerung.jpg

An alternative would be to use the command line. Just launch the Command Prompt and type the following line, then press Enter:


That will show your FQDN.

To look for your FQDN on a Mac, open Terminal. Type “hostname -f” into the prompt. You should see your computer’s FQDN.

On a Linux computer, open Terminal. Type “hostname -A” into the prompt. Note that “A” is case-sensitive. You should then see your computer’s FQDN.

What Is an FQDN Used For?

We went through what FQDNs are for in brief earlier. Let’s dive deeper into each now.

1. Getting an SSL Certificate

An SSL certificate binds a domain with a server name or hostname. It is installed on a server to tie an organization’s identity to the server’s location. Because of that, such a certificate only gets granted to an FQDN. Note that all websites that handle the transfer of money and sensitive information (all business sites) must have an FQDN. An example would be www[.]geocerts[.]com.

Source: https://cdn.buttercms.com/ME6vUFNQRaSIrSKuixUA

2. Remotely Connecting to a Host

There are times when you can’t connect to a remote computer using its IP address. If that happens, you need to specify its FQDN instead. The said machine’s Domain Name System (DNS) server will look for the FQDN in its DNS table and translate it into its IP address. Once all that is done, you can access the computer you’re looking for. An example of an FQDN when remotely accessing a computer is hostname[.]d[.]ethz[.]ch.

Source: https://www.it.mavt.ethz.ch/wp-content/uploads/2020/03/img_5e70c3db97d51.png

3. Access a Specific Domain Service or Protocol

Any activity that involves transferring data on the Internet requires accessing the DNS. If you want to access your company’s FTP server, for example, you need to know its FQDN or IP address. An example of an FQDN for an FTP folder is ftp[:]//ftp[.]domain[.]com.

Setting up your email accounts on your smartphone requires you to know the FQDN of the email server as well, specifically for the incoming and outgoing mail server fields. An example would be mail[.]mt-domain[.]com.

Source: https://mediatemple.zendesk.com/hc/article_attachments/360051613952/dv1.png

If you didn’t know what an FQDN was before and what it’s for, you were probably surprised that you’d encountered one at least once before.