What is Localhost?

In computer networking, the term “localhost” refers to the current device used to access it. It is used to access the network services that are running on the host via the loopback network interface. Using the loopback interface bypasses any local network interface hardware.

The term “localhost” is derived from the combination of the words “local” and “host”. The word “local” refers to the device itself, while the word “host” refers to the device hosting a service or application. Therefore, “localhost” literally means “the local host.”

In most cases, localhost is used to access the network services that are running on the same device as the one being used to access them. For example, if you are running a web server on your local computer, you can use the URL “http://localhost” to access the web server from the same computer.

The `loopback` network interface is a virtual network interface that is used to communicate with the host’s own network services. It is not associated with any physical network interface, and all traffic sent to the loopback interface is looped back to the host. The loopback interface is assigned the IP address `127.0.0.1`, which is a special IP address reserved for the loopback interface.

ip addr show lo 

Output
1: lo:  mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever

The loopback interface is useful for testing network services and applications on a single device without the need for a network connection. It is also useful for accessing network services and applications from different locations on the same device, such as from different user accounts or virtual machines.

Examples:

Here are some examples of how localhost can be used:

• Accessing a web server running on the local device: To access a web server running on the local device, you can use the URL “http://localhost” or “http://127.0.0.1” in a web browser. This will connect to the web server via the loopback interface and display the website hosted on the local device.
• Testing a network service: To test a network service, such as a web server or database server, you can use the loopback interface to connect to the service from the same device. This allows you to test the service without the need for a network connection.
• Accessing a service from a different location on the same device: To access a service from a different location on the same device, such as from a different user account or virtual machine, you can use the loopback interface to connect to the service. For example, if you are running a web server on a virtual machine, you can use the URL “http://localhost” from the host machine to access the web server.

Conclusion:

In summary, localhost is a term used to access the network services that are running on the current device via the loopback network interface. It is useful for testing network services and applications on a single device, and for accessing services from different locations on the same device.