> ## Documentation Index
> Fetch the complete documentation index at: https://docs.tryblox.app/llms.txt
> Use this file to discover all available pages before exploring further.

# Mobile Preview

> Test your app on physical devices in real-time

Testing on physical devices is crucial for mobile development. Blox provides a seamless bridge from your browser to your phone.

## Using the QR Code

Every Blox project has a unique development QR code. Scanning this in the **Blox Preview** app connects your device to the local dev server.

### Prerequisites

1. Download the **Blox Preview** app from the App Store.
2. Ensure your phone and computer are on the same Wi-Fi network (or use a Tunnel).

## Live Reloading

Blox uses a specialized Hot Module Replacement (HMR) engine.

* **UI Updates**: When you change a color or font, your phone refreshes instantly.
* **Logic Updates**: Changing API calls or state logic will trigger a fast refresh, preserving your app's state.

## Debugging

You can view logs and errors directly in the browser console of the Blox Editor.

<Warning>
  Large assets (unoptimized images) may slow down initial load times on the preview app. We recommend using SVG where possible.
</Warning>

## Simulator Access

If you don't have a physical device handy, you can use the **In-Browser Simulator**. This uses an emulated environment to show you exactly how your app will look on various screen sizes.

<Card title="Open Simulator" icon="desktop" href="/builder">
  Enter the Blox Builder to launch the browser simulator.
</Card>