A fully qualified domain name (FQDN), also known as an absolute domain name, is the complete address used to identify a specific location on the internet. It shows exactly where a resource lives within the Domain Name System (DNS) hierarchy, including every level from the hostname to the top-level domain (TLD) and root.
Because it includes every part of the domain, an FQDN points to one precise destination. There is no ambiguity, which allows browsers and servers to consistently find the correct resource every time.
Components of an FQDN
An FQDN is made up of a hostname and a domain name separated by periods. The standard format looks like this: hostname.domain.TLD. The domain portion can also include subdomains.
For example, in www.godaddy.com, “www” is the hostname, “godaddy” is the second-level domain (SLD), and “.com” is the TLD.
Here’s another example to show how these pieces work together. If your company provides Single Sign-On for your email, it should look like this:
- Hostname: sso
- Domain: godaddy.com
- FQDN: sso.godaddy.com
This structure makes it possible to run multiple services within the same domain. Each server, such as web, mail, or FTP, can have its own unique FQDN while staying connected to the same domain.
Reading an FQDN
FQDNs are read from right to left, starting with the root, moving through the TLD, and ending with the hostname.
You may sometimes see an FQDN written with a trailing period (e.g., www.GoDaddy.com.). This final dot represents the root of the DNS. Most browsers and tools handle this automatically, so the trailing period is usually left out in everyday use.
However, the trailing period is crucial in more technical settings. DNS zone files often require it to ensure the domain is treated as absolute rather than relative to the current zone. Some server configurations and DNS tools also expect the dot for proper parsing.
Understanding DNS resolution
DNS resolution is the process that turns a domain name into an IP address so browsers and servers can communicate. When you enter a domain into your browser, a series of DNS queries work behind the scenes to locate the correct server and deliver the requested content. Let’s take a closer look at what this is and how it works.
Recursive and iterative DNS lookups
DNS resolution involves two main types of queries: recursive and iterative. In a recursive DNS lookup, the DNS resolver queries multiple DNS servers until it returns the final, authoritative answer.
In an iterative DNS lookup, the resolver receives referrals to other DNS servers and queries each one step-by-step until it finds the IP address.
Both methods ensure the domain name is accurately translated into its corresponding IP address.
DNS caching benefits
DNS caching stores previously resolved domain names locally, reducing the need for repeated queries and accelerating the resolution process. With cached DNS responses, browsers and resolvers can retrieve IP addresses without traversing the entire DNS lookup chain, enhancing overall performance and efficiency.
Step-by-step DNS lookup process
A DNS lookup typically follows these steps:
- A user enters a domain name into a web browser.
- The DNS resolver checks its cache for the IP address.
- If not cached, it queries the root nameserver.
- The root nameserver directs it to the TLD nameserver (e.g., .com).
- The TLD nameserver points to the authoritative nameserver for the domain.
- The authoritative nameserver provides the IP address of the domain.
- The resolver caches the IP address and returns it to the browser, which then loads the webpage.
How to look up a fully qualified domain name
Finding the FQDN for your computer or server is usually quick, but it depends on your system setup. In some cases, an FQDN will only be available if the device is connected to a domain or has been configured with one. If your system does not provide the FQDN, it is not connected to a domain.
Follow the instructions for your operating system below.
Windows 11
- In the taskbar’s “Search Windows” box, type “Control Panel” and select “System and Security.”
- Next, select “System,” and the FQDN is listed under Device Specifications, next to the Device Name.
macOS
- Open Terminal and enter hostname into the prompt.
- Terminal will return the FQDN.
Linux
- Open Terminal and enter hostname -A into the prompt. The A is case sensitive.
- Terminal will return the FQDN.
FQDN use cases
In general, an FQDN is required to make a computer, device, or entity accessible on the internet. However, defining an FQDN locally isn’t sufficient to bring it online.
You must update the DNS record in the DNS settings so the DNS knows the specific location of the device. Defining your DNS namespaces allows the DNS to connect the FQDN to IP addresses, thereby locating your device online.
Internal network identification
FQDNs play an important role in helping teams find and connect to resources within internal networks, such as file servers, print servers, databases, and development environments.
Organizations often use private DNS to map these internal FQDNs to private IP addresses, like those in the 192.168.x.x or 10.x.x.x ranges. This makes it easier to access resources using clear, recognizable names like fileserver.internal.company.com instead of remembering numeric IP addresses.
It’s crucial to keep internal domains private. Publishing them on public DNS servers can expose details about your network structure and create potential security risks. Keeping internal and public DNS separate helps protect your systems and data.
Obtaining an SSL certificate
SSL certificates are small data files that bind a domain to its server name or hostname. They are installed on a server to tie an organization’s identity to its location and are only granted to FQDNs.
GoDaddy provides a variety of SSL options to suit different business needs, including Standard SSL, Wildcard SSL, and Extended Validation (EV) SSL certificates. Read our guide on how to add an SSL and increase site security to learn more.
Connecting to a host remotely
If you don’t want to or can’t connect to a remote host or virtual machine (VM) via raw IP, such as through SSH, you need to specify the FQDN. The DNS server resolves the FQDN to its IP address, contacts the host, and returns a login prompt.
If you’re using an application to connect to a server, you might need the FQDN so the DNS can find the server. For remote hosts outside your ISP, the FQDN is typically required.
Accessing specific domain services or protocols
Essentially, any activity that transfers information across a network involves DNS and therefore requires an accessible FQDN. Whether connecting to a File Transfer Protocol (FTP) server or an email server, knowing its FQDN or IP address is necessary. For example, setting up email on your smartphone often requires knowing the email server's FQDN.
Wrapping up: Why FQDNs matter
FQDNs are a foundational part of how the internet works, even if they often operate behind the scenes. Understanding how FQDNs are structured, how they’re used, and how to find them can make managing domains and troubleshooting network issues much more straightforward. With a solid grasp of these basics, you’re better equipped to navigate everything from everyday browsing to more advanced DNS configurations.
Frequently Asked Questions
What is the difference between an FQDN and DNS?
A Fully Qualified Domain Name (FQDN) is the complete domain name of a specific host or computer on the internet, including the hostname and domain name, such as www.example.com. DNS (Domain Name System) is the system that translates these domain names into IP addresses, allowing browsers to load internet resources efficiently.
What is the difference between an FQDN and a URL?
A fully qualified domain name (FQDN) is the complete domain name that identifies the exact location of a resource within the Domain Name System (DNS), such as www.example.com. A URL (Uniform Resource Locator) is the full web address used to access that resource. It includes the FQDN along with additional details like the protocol, path, query parameters, and fragments. For example, https://www.example.com/page?id=123#top includes the FQDN www.example.com, plus everything needed to load a specific page.
What is the difference between an FQDN and an ADN (Absolute Domain Name)?
The terms fully qualified domain name (FQDN) and absolute domain name (ADN) are often used interchangeably. In most cases, they mean the same thing: a domain name that includes the full hierarchy needed to point to a specific location in DNS. If you see “absolute domain name” in technical documentation, it typically refers to an FQDN.
What is the difference between an FQDN and a PQDN?
A partially qualified domain name (PQDN) does not include the full set of labels needed to specify an exact location in DNS. It provides only part of the domain path. For example, www.example.com is a fully qualified domain name, whereas example.com is a PQDN because it does not include the hostname. In practice, many websites are configured to handle both formats and direct users to the same destination, regardless of how the domain is entered.
Can an FQDN be an IP address?
No, an FQDN cannot be an IP address. An FQDN is a human-readable domain name that uniquely identifies a host on the internet, whereas an IP address is a numerical label assigned to each device connected to a computer network. DNS is used to translate FQDNs into their corresponding IP addresses.
