Glossary: Building APIs with Node.js

Host addresses (127.0.0.1, 0.0.0.0)

Also written: 127.0.0.1, 0.0.0.0, loopback, HOST=0.0.0.0

`127.0.0.1` is the loopback address, reachable only from the same computer; Fastify listens there by default, so kc-api stays private while you develop. `0.0.0.0` means "listen on every network interface", so on a host you set `HOST=0.0.0.0` to let outside requests reach the app.