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An internet domain name is a name in the Domain Name System (DNS) that identifies a node in DNS’s hierarchy. For example, www.icann.org is a domain name: its labels are separated by dots, with the most specific label first and the top-level domain last. The name is not a website, a URL, or DNS itself.
What a domain name identifies
DNS is organized as a tree. Each point in that tree is a node with a label, and a domain name is the sequence of labels along the path from that node to the root. As RFC 1034 puts it, “The domain name of a node is the list of the labels on the path from the node to the root of the tree.” In ordinary writing, the labels appear from most specific to least specific, separated by dots. RFC 1034, section 3.1
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A domain name identifies a node; the domain is the part of the name-space tree at or below that node. The terms are closely related, but they do not mean exactly the same thing. RFC 1034
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How the labels fit together
In whois.icann.org, each dot marks a boundary between labels. Read from right to left to see the hierarchy:
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orgis the top-level domain (TLD).icannis the second-level label.whoisis the third-level label, commonly called a subdomain.
The root sits above the TLD in the DNS hierarchy, though the root is not usually shown in everyday written domain names. ICANN’s domain-name explainer describes this example and the hierarchy; IANA’s overview explains the root zone and TLD delegation.
Domain name, DNS, website, and URL: what is the difference?
| Term | What it is | What it does or means |
|---|---|---|
| Domain name | A hierarchical name identifying a node in DNS, such as example.com. |
Provides a name that can be queried for associated DNS information. |
| DNS | The naming system and protocols, including name servers, resolvers, and resource records. | Answers queries for particular kinds of information associated with names, including host address information. |
| Website or URL | A website is a service; a URL is a locator that can include a domain name. | A website or other service may use a domain name, but registering the name does not create the service. |
It can help to think of DNS as a system for looking up named resources, but it is more precise to say that queries ask for particular kinds of resource data associated with a name. A domain name is one of the names used within that system. RFC 1034
What registration does—and does not do
Registering a domain name gives a realm in DNS a name. It does not, by itself, publish a website or provide email. To make a site reachable, the name must be configured to point to a web service; email likewise depends on an email service and the relevant DNS configuration. A site can use the registered name or a subdomain. ICANN’s domain-name explainer
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DNS authority is organized hierarchically. Authority over a name can be delegated down the tree, so separate parties can administer different levels or branches. IANA’s description of root-zone management covers TLD delegation, while ICANN’s explainer describes how names are organized and delegated. IANA: Domain Name Services · ICANN: About Domain Names
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What a fully qualified domain name means
A fully qualified domain name (FQDN) gives the full path of labels to the DNS root, identifying a name’s exact position in the hierarchy. The root may be represented explicitly in DNS notation, although everyday examples commonly omit it. ICANN’s FQDN terminology entry
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