What is Host



A host is a computer that is accessible over a network. It can be a client, server, or any other type of computer. Each host has a unique identifier called a hostname that allows other computers to access it.

Depending on the network protocol, a computer’s hostname may be a domain name, IP address, or simply a unique text string. For example, the hostname of a computer on a local network might be Tech-Terms.local, while an Internet hostname might be A host can access its own data over a network protocol using the hostname “localhost.”


Also called a computer namenodename, or sitename, a hostname is the name of a computer or device (host) on a network.

Hostname examples

Below is an example of a hostname that is assigned to a computer connecting to the Internet using Comcast.


As can be seen in the example above, this hostname has the IP address (, “CO” for Colorado, and comcast.net, which is the ISP hosting the customer. This type of hostname would be stored in a Domain Name System to help with mapping the hostname to an address.

Local network hostname example

Another example would be a local network called “hope” with two computers on that network called “bart” and “homer.” On this network, the “bart” computer would have a hostname “bart.hope” and the “homer” computer would have the hostname “homer.hope.”

Internet hostname examples

On the Internet, a hostname is a domain name assigned to a host computer. For example, if Computer Hope had two computers on its network named “bart” and “homer,” the domain name “bart.computerhope.com” is connecting to the “bart” computer. The IP address of the “bart” computer is obtained by looking up the hostname “bart.computerhope.com” in the host’s file or DNS resolver.

Hostname rules and restrictions

Below are a few rules and restrictions that must be followed for a hostname to be valid.

  1. A hostname is a single word with no spaces.
  2. A hostname may only have letters, numbers, periods, or a hyphen.
  3. A hostname has a maximum length of 253 characters.
  4. A DNS (Domain Name System) name may be appended to a hostname.
  5. The hostname cannot have an underscore. However, an appended DNS contained in the hostname may have an underscore.
  6. The early hostname specification in RFC 952 required that a hostname not begin with a number or hyphen character. However, this restriction was later changed in RFC 1123.

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