Overview

ngrok is an HTTP tunneling tool. It can be used to expose a locally running server to the outside world using HTTP or HTTPS.

ngrok has Free, Pro, and Enterprise tiers. Basic usage is free.

Steps to Use

1. Sign up for an account at ngrok.
2. Login at the same URL.
3. Download an OS-specific version of the ngrok command.
4. Copy your auth token from the "Setup & Installation" page.
5. Authenticate with ngrok by entering the command ngrok authtoken {your-auth-token}
6. Start any local server that listens on a given localhost port.
7. Create a tunnel by entering the command ngrok http {local-port-number}
8. In the output of this command, copy the URL after "Forwarding". Note that there are two to choose from: one for http and one for https.
9. Use the copied URL from any device to send HTTP requests to the local server.

A limitation of the Free tier is that the forwarding URLs are ephemeral, meaning they change each time the ngrok command creates a new tunnel. Code that uses an ngrok URL must be modified to use the new value. The Pro and Enterprise versions can use a custom domain, removing this burden.