What does FQDN mean?

The FQDN or Fully Qualified Domain Name , written in the hostname and domain name, includes the top-level domain name, in the following order: [host name]. [Domain]. [Tld].

In this case, "qualified" means "specified" because the entire location of the domain is defined in the name. FQDN determines the exact location of the host in DNS. If this name is not specified, it is called a Partially Qualified Domain Name or PQDN. More information about PQDN will be mentioned at the end of this page.

An FQDN can also be called an absolute domain name, as it provides the absolute path of the host.

Example of FQDN

An FQDN is always written in this format: [host name]. [Domain]. [Tld] . For example, a mail server on domain example.com can use FQDN mail.example.com.

Here are some other examples of FQDN:

1. www.microsoft.com
2. en.wikipedia.org
3. p301srv03.timandtombreadco.us

Domain names that are not "fully qualified" will always have a vague element. For example, p301srv03 cannot be FQDN because any number of domains can have a server with that name.'p301srv03.wikipedia.com' and 'p301srv03.microsoft.com' are two other examples - just knowing hostnames doesn't help much for you.

Next, microsoft.com is not fully qualified because we don't know what hostname is, even if most browsers automatically assume that it is www.

Domains that are not fully qualified are called Partially Qualified Domain Name (details are available in the next section).

The FQDNs actually require a dot at the end, ie www.microsoft.com. will be the way to enter the accepted FQDN. However, most systems will include that dot, even if you don't explicitly provide it. Some web browsers may even allow you to enter a dot at the end of the URL but are not required.

Partially Qualified Domain Name (PQDN)

Another term similar to the FQDN is the PQDN or Partially Qualified Domain Name . This is just a domain name that is not fully defined. The example p301srv03 above is PQDN, because although you know the hostname, you don't know which domain it belongs to.

PQDN is used for convenience, but only in certain contexts. They are for special situations when hostname reference is easier without referring to the entire FQDN. This is possible, because in these contexts, the domain is already known elsewhere and therefore only requires a hostname for a specific task.

For example, in DNS records, admin can refer to a FQDN like en.wikipedia.org or simply shorten it and use the hostname en. If it is shortened, the rest of the system will understand that in that particular context, en is actually referring to en.wikipedia.org.

However, you should understand that the FQDN and PQDN are certainly not the same. A FQDN provides the full absolute path of the host, while the PQDN only provides relative names, a small part of the full domain name.