A fully qualified domain name (FQDN) is a domain name that specifies not only the top-level domain and parent domain name, but also the localhost.

These more specific domain names show additional information about the origin of a Web page in a true uniform resource locator (URL).
In other words, FQDN  is a domain name that gives the exact location of the node in the DNS tree, which represents all top-level domains. We are also talking about an absolute rather than a relative field.

In a DNS configuration, the FQDN is dotted with an endpoint that represents the root domain. E.g :

  •  commons.wikimedia.org. is an FQDN because no parent subdomains are skipped and ends with an endpoint.
  •  commons and commons.wikimedia are not FQDNs because top level domains are omitted.


The idea behind a full domain name is that it handles ambiguity in some domain entries. A browser or other system may not be able to correctly locate a target unless each piece of information is specified.

In some ways, having a fully qualified domain name is the same as having a fully qualified PC-DOS command to locate a single file or folder in a traditional personal computer's hierarchical data storage system. A fully qualified domain name is a reference to a new resource that allows specific access to resources over the public Internet.

A problem with the fully qualified domain name involves resolving these domain entries. Organizations such as the Internet Engineering Task Force have defined specific resolution processes for fully qualified domain names to aid in consistent communication.