What is localhost?

Localhost is a networking term for the hostname of the current server or computer accessing the network. It is used via the loopback network interface to access the network services running on the host. The loopback interface bypasses any local network interface hardware and serves as a method to connect back to the server. Networking and server administration both frequently use the term localhost.

Local Loopback

The local loopback mechanism runs a network service on a host without requiring a physical network interface or making the service accessible from the networks to which the computer is connected. For example, a locally installed website may be accessed from a browser by the URL http://localhost to display its home page.

The hostname localhost typically resolves to the IPv4 and IPv6 loopback IP addresses.

IPv4 localhost

The IPv4 address for localhost, or the loopback network interface, is 127.0.0.1.

IPv6 localhost

The IPv6 address for localhost, or the loopback network interface, is ::1.

For What is localhost Used?

Use cases for localhost are typically related to network administration and development testing. For example, administrators can test network speeds and performance while developers test their applications and websites in a siloed environment.

Speed Testing

Network administrators ensure all equipment and the TCP/IP function properly by testing connections and sending ping requests to the localhost.

With a terminal set up to ping, they can run the commands ping localhost or ping 127.0.0.1 and view its performance. This data allows administrators to pinpoint and fix issues if they exist.

Application and Website Testing

Developers use localhost to test websites or applications that typically require an internet connection. They use a loopback to connect to the localhost and try them inside the computer or system they are currently using. In this instance, the operating system (OS) becomes a simulated web server, loading the necessary files into the web servers and allowing developers to check the site or application's functionality.

Wrapping Up

It is helpful to know what localhost is and how to use it to your advantage. Both developers and network administrators benefit from this understanding, allowing them to perform tasks internally without outside traffic and threats.

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