Learn about Fully Qualified Domain Names (FQDNs), how they differ from other domain names, and how F5 can help.
A fully qualified domain name (FQDN) is a complete, unambiguous domain name that specifies the exact location of network resources, such as servers, websites, or services, on the Internet. FQDNs facilitate the organization, identification, and access of online resources, ensuring interoperability across diverse networked environments.
The FQDN serves to show the exact location of a computing resource inside the Domain Name System (DNS) hierarchy. An FQDN is traditionally written as a list of domain labels: the top-level domain, the second-level domain name, a subdomain (if used), and the host domain, each separated by dots or periods. The label hierarchy is read from right to left. As an example of FQDN syntax, in the address www.shop.example.com the “.com” is the top-level domain, “example” is the second-level domain name, “shop” is the subdomain, and the “www” is the hostname.
Traditional domain names are based on the ASCII character set, which includes the Latin alphabet and a limited set of characters. However, many languages around the world use scripts with characters that are not represented in ASCII. International domain names (IDNs) address this limitation by allowing the registration and use of domain names in local languages and scripts.
IDNs are domain names that include characters from non-ASCII character sets, such as letters with diacritics or characters from non-Latin scripts. IDNs enable the use of domain names in languages other than English and support the inclusion of characters from various scripts and writing systems, promoting inclusivity and linguistic diversity on the Internet.
IDNs use Unicode, a standardized character encoding system, to represent non-ASCII characters. Unicode assigns unique numeric values to characters and symbols from virtually all the world's writing systems, allowing domain names to include characters from various scripts, such as Cyrillic, Arabic, Chinese, Japanese, Korean, and many others, beyond the limited set of characters available in the ASCII character set.
In turn, another encoding system called Punycode converts the non-ASCII IDNs into ASCII-compatible representations. This allows domain names containing characters from various scripts to be represented in a format that is compatible with the ASCII character set, which is traditionally used for domain names in the DNS.
According to ICANN, the terms "Fully Qualified Domain Name" and "Absolute Domain Name" are often used interchangeably, and in most contexts, they refer to the same concept. Both terms describe a domain name that includes the full hierarchy of labels needed to specify the exact location of a resource in the DNS.
A PQDN is a domain name that lacks the complete hierarchy of labels necessary to make it a FQDN; a PQDN does not provide the full path needed to locate a specific resource on the Internet. Commonly, a PQDN lacks the hostname, so while www.example.com is that site’s FQDN, “example.com” would be that site’s PQDN. Most website developers configure their site’s DNS to redirect visitors to the same page whether they key in the FQDN or PQDN.
A FQDN is a complete domain name that specifies the exact location of a resource in the DNS, while a URL refers to the full address for accessing resources on the Internet, including the protocol and additional components beyond the domain name. URLs are commonly used in web browsers to navigate to specific web pages.
FQDNs serve a number of important functions, including:
FQDNs play a crucial role in identifying, connecting, and securing network infrastructure, communication, and web services. These uses include:
How to find your computer’s FQDN depends on your operating system.
Alternatively, in macOS, opening the terminal and typing hostname -f into the prompt returns the FQDN.
Opening the terminal and entering hostname -A, where the A is case-sensitive, into the prompt will return the FQDN.
DNS enables users to access services, making it one of the most important components in the network infrastructure. If DNS is unavailable, services won’t function properly. F5 BIG-IP DNS and F5 Distributed Cloud DNS offer unmatched DNS performance, managing query responses with multicore scalability and handling spikes in DNS query volume to make sure apps are highly available—even between multiple instances and across hybrid environments. F5 DNS platforms offer simple management, with easy visibility and programmability, ensuring that network architectures are easier to maintain and providing faster web browsing and reduced latency for improved user experiences.