Dictionary · Networking Fundamentals
Loopback Address
Addressing · Beginner
An address that sends traffic back to the same host. The familiar values are 127.0.0.1 and ::1, with the entire 127.0.0.0/8 block reserved in the 32-bit protocol.
It lets a program talk to another program on the same computer without leaving the machine. Testing a local web server this way does not prove the server is reachable from the network.
Example: A developer opens http://127.0.0.1:3000 to view an application that is running only on that computer.
Common misconception
- Traffic to 127.0.0.1 does not test the network cable, switch, or public address.