Localhost Deep Dive: 127.0.0.1 vs 0.0.0.0 Explained

If you've ever started a web server, you've likely seen these two addresses. While they look similar, they serve completely different roles.

127.0.0.1: The Loopback

Commonly known as localhost, 127.0.0.1 refers to the machine you are on. When a server binds here, it is invisible to the outside world.

0.0.0.0: The Wildcard

0.0.0.0 means "Listen on all available network interfaces." If your server binds here, it will be accessible via localhost, your local Wi-Fi IP, and your public IP.

Which One Should You Use?

Use 127.0.0.1 for private local development and 0.0.0.0 when you need the service to be reachable from other devices or inside a Docker container.