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IP Address Lookup

The following is for informational purposes only



What is a Hostname?

A hostname (also known as a "node name", "computer name", or "site name") is a unique Fully Qualified Domain Name (FQDN) that identifies every hardware device (host) connected to the internet via the Domain Name System (DNS) naming hierarchy. Historically, hostnames represented a name resolution for IP addresses.

They are the absolutely and uniquely differentiating addresses that computers use to communicate with each another within a network, be it local network (LANs) or global networks like the internet.

Simply put, the hostname is the nickname given to any computer or device hooked up to a computer network. Each internet user gets this one-to-one description, regardless of whether it's a network node at the internet provider, a computing machine, or a web server.

Since hostnames are frequently confused with domains, it's good to know that multiple hosts can be grouped under one domain, just like subdomains. Sometimes domain names are the same as hostnames, but this is not a general rule. In IT architecture, hostnames have the role of differentiating clients.

Hostname vs IP Address

A hostname is the concatenation of a computer's name and a domain name ( The role of a hostname is to increase readability since it's easier to remember than an IP address. In many situations, hostnames and IP addresses are considered interchangeable simply because all hostnames are linked to IP addresses.

Hostname Example: How does a Valid Hostname Syntax Look Like?

Hostname Example: How does a Valid Hostname Syntax Look Like?

According to the RFC 1123 protocol, the hostname's total length is limited to 255 characters, and it comprises the hostname and the domain name labels separated by periods.

Here is an example of a typical hostname that would be stored in a DNS for geolocating the hostname's address and would be assigned to a PC connected to the internet via Comcast: "" where: is the hostname's IP address, "CO" stands for Colorado, and is the ISP hosting the end-user.

On the internet, a hostname refers to the domain name attributed to a host computer. For instance, if Computer Ben's network has two computers named "River" and "John", the domain name "" connects to the "river" computer. The IP address of the "river" computer is acquired by looking up the hostname "" in the host's file or DNS resolver.

If we refer to an internet location or a website (for instance,, the hostname is typically seen as a domain name and is within the address typed into a web browser to access a webpage. When it contains a Top-Level Domain (TLD), the hostname is considered an FQDN. For instance, the format of an internet address is where:

  • "HTTP" is the protocol.
  • "www" is the hostname.
  • "exampledomain" is the domain name.
  • "com" is the TLD.
  • "examplefile.html" is the file path.

Hostname Assignment Guidelines

Hostname Assignment Guidelines

Depending on the network type and protocol, hostnames must meet international standards and follow specific rules:

  • For private networks: Hostname assignment is somewhat spontaneous in a VPN, intranet, or LAN.
  • For public networks: In the World Wide Web, hostnames must comply with internet protocols, such as Protocol RFC 1123, and get listed as FQDNs, facilitating direct resolution to an IP address.

Hostnames naming conventions, rules, and restrictions include:

  • A single word sequence with no spaces but with segments separated by periods.
  • Only characters from the ASCII character set (numbers, letters, periods, or a hyphen).
  • A DNS name can be appended to a hostname.
  • No, underscore, unless it's for an attached DNS within the hostname.

The RFC 1123 protocol specifically recommends the following:

  • Valid hostnames start with a number or a letter.
  • The domain name cannot end with a hyphen.
  • Admitted length is limited to 255 characters.

The sequence between periods is a label. Labels cannot end or begin with a hyphen and can only have between 1 and 63 characters.

How to Find Hostname?

How do I Find My Hostname?
  • On a Mac: choose Apple menu -> System Preferences -> click Sharing, and at the top of Sharing preferences, under the computer's name, you'll see your computer's local hostname.
  • On a Windows computer: Start -> (All) Programs -> Accessories -> Command prompt. In the new pop-up window, enter "ipconfig /all", press Enter, and you will see the hostname of the machine, less the domain at the top, under the section Windows IP Configuration.
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