A Fully Qualified Domain Name, usually shortened to FQDN, is the complete name used to identify a specific computer, server, or service on the internet.
For example: server1.example.com
In this example:
- server1 is the hostname.
- example is the domain name.
- .com is the top-level domain (TLD).
Put everything together and you have the fully qualified domain name: server1.example.com
What Does "Fully Qualified" Mean?
"Fully qualified" simply means that the complete name has been provided.
A hostname such as server1 does not tell the internet which domain the server belongs to.
When we add the domain, server1.example.com, we now have enough information to identify the server within the internet's Domain Name System (DNS).
What Is the Difference Between a Domain Name and an FQDN?
A domain name identifies a domain, while an FQDN can identify a specific host or service within that domain.
For example:
Domain name: example.com
FQDN: mail.example.com
The domain is example.com, while mail.example.com could identify the server responsible for handling email.
Another example might be: webserver.example.com
Here, webserver is the hostname and example.com is the domain.
What Is a Hostname?
A hostname is the name assigned to a computer or server.
Common examples include: server1, web01, mail, vps1
When a hostname is combined with a domain name, it can form an FQDN.
For example:
Hostname: mail
Domain: example.com
FQDN: mail.example.com
Is www.example.com an FQDN?
Yes. www.example.com can be considered a fully qualified domain name because it identifies the www host within the example.com domain.
The same is true for names such as: mail.example.com, portal.example.com, server1.example.com, shop.example.com
These are also commonly called subdomains because they exist underneath the main domain.
Does an FQDN Have to Be a Website?
No. An FQDN can identify many different types of systems and services.
For example:
- www.example.com could be a website.
- mail.example.com could be a mail server.
- server1.example.com could be a VPS or dedicated server.
- ftp.example.com could be used for an FTP service.
The name itself does not determine what the server does. DNS records and the services running on the server determine where the name points and what happens when someone connects to it.
Why Do Servers Need an FQDN?
Servers commonly use an FQDN as their hostname so other systems can identify them properly.
For example, a server might use: server1.example.com instead of simply: server1
A properly configured FQDN can be important for web hosting control panels, email servers, SSL certificates, DNS, and other server software.
If you order a VPS or Dedicated Server, you may be asked to provide a hostname. An FQDN is normally the best choice.
What Should I Use for My Server's FQDN?
Choose a hostname that belongs to a domain you control.
For example, if you own mycompany.com you could use server1.mycompany.com or vps1.mycompany.com.
You could also use a name that describes the server's purpose:
mail.mycompany.com, web1.mycompany.com, dns1.mycompany.com
The exact name is mostly your choice, but it should be unique and should use a domain that you control.
Does an FQDN Need a DNS Record?
If other computers on the internet need to reach the server using its FQDN, you should create the appropriate DNS record.
For example, you could create an A record: server1.example.com → 192.0.2.10
This tells DNS that server1.example.com should point to the IPv4 address 192.0.2.10.
For IPv6, an AAAA record is used instead.
What Is Reverse DNS?
Normal DNS takes a name and finds its IP address: mail.example.com → 192.0.2.10
Reverse DNS, also called rDNS, does the opposite: 192.0.2.10 → mail.example.com
Reverse DNS is especially important for mail servers because receiving email systems often check the hostname associated with the sending server's IP address.
If you operate your own mail server, it is generally a good idea for its hostname, DNS records, and reverse DNS to be configured correctly.
Is an FQDN the Same as an IP Address?
No. An FQDN is a human-readable name, while an IP address identifies a device or server on a network.
For example:
FQDN: server1.example.com
IPv4 address: 192.0.2.10
DNS connects the two by telling computers which IP address belongs to the FQDN.
This makes names much easier to remember than having to use IP addresses for everything.
Can More Than One FQDN Point to the Same Server?
Yes. A single server can have many domain names and FQDNs pointing to the same IP address.
For example: example.com, www.example.com, shop.example.com and blog.example.com could all point to the same server.
Web hosting software can then determine which website should be displayed based on the domain name the visitor requested.
Do I Need to Buy a Separate Domain for an FQDN?
No. If you already own a domain, you can normally create hostnames or subdomains underneath it without registering additional domains.
If you own example.com, you could create: server1.example.com, mail.example.com, vps.example.com, and many other names without purchasing each one separately.
You simply create the necessary DNS records for them.
What Is an Example of a Good FQDN?
If you own example.com and have a VPS, a simple FQDN could be: vps1.example.com
If you have several servers, you might use: web1.example.com, web2.example.com, mail1.example.com, dns1.example.com
Using clear names can make it easier to identify your servers later.
Do I Need an FQDN for Web Hosting?
You usually do not need to think about FQDNs when using a normal Web Hosting or Reseller Hosting account. Most of the server configuration is handled for you.
FQDNs become more important when managing your own VPS, Dedicated Server, mail server, DNS server, or other internet services.
In simple terms, an FQDN is just the complete internet name of a server or host.
If server1 is the server's name and example.com is your domain, then: server1.example.com is its fully qualified domain name.
