networking//Localhost

- `127.0.0.1` is the loopback address — traffic never leaves the machine.

127.0.0.1 is the loopback address — traffic never leaves the machine.

NOT part of the private IP ranges (not 10.x.x.x or 192.168.x.x) — its own special class.

localhost:3000 on your machine is invisible to other LAN devices.

Inside a Docker container, localhost refers to the container itself, not the host.

Each container has its own loopback — ping localhost inside a container hits the container.