(also IP address 127.0.0.1, localhost)
A loopback address is an IP address you can use to loop and return data packets through a network interface card. The loopback address starts with the following numbers: 127.0.0.1. If you send data packets to a loopback address, they won’t reach the address. Instead, they will get looped through your network interface card and returned back to where you sent them from. You can use a loopback address to test your communication channels without modifying or processing the data you send. Most businesses use it to check their internal paths. 127.0.0.1 is the most common loopback address used in IPv4, but there are also other loopback addresses you can use, going up to 127.255.255.255.