Preview

When your app starts and listens on a port, The Box automatically creates a dynamic subdomain with HTTPS for it. The app is immediately accessible at that URL — no extra configuration needed.

The Preview panel is a simple browser built into The Box. It shows your app and has an address bar — you can navigate between pages inside the app.

The subdomain URL works in any browser — on your phone, on another computer, share it with someone. The app is accessible as long as the container is running.

If your app listens on multiple ports — each gets its own subdomain. Switch between them using the port selector in the Preview panel's address bar.