In computer networking, localhost is a hostname that 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 local loopback mechanism may be used to run a network service on a host without requiring a physical network interface, or without making the service accessible from the networks the computer may be connected to. For example, a locally installed website may be accessed from a Web browser by the URL http://localhost to display its home page.
The name localhost normally resolves to the IPv4 loopback address 127.0.0.1, and to the IPv6 loopback address ::1.[1]
IPv4 network standards reserve the entire address block 127.0.0.0/8 (more than 16 million addresses) for loopback purposes.[2] That means any packet sent to any of those addresses is looped back. The address 127.0.0.1 is the standard address for IPv4 loopback traffic; the rest are not supported by all operating systems. However, they can be used to set up multiple server applications on the host, all listening on the same port number. The IPv6 standard assigns only a single address for loopback: ::1.
The resolution of the name localhost to one or more IP addresses is normally configured by the following lines in the operating system's hosts file:
The name may also be resolved by Domain Name System (DNS) servers, but queries for this name should be resolved locally, and should not be forwarded to remote name servers.