Creating a Desktop App with Expo and Tauri

Step-by-step guide to building a cross-platform desktop app

Highlights

Unified Codebase: Develop your UI and business logic in a single Expo project that serves mobile, web, and desktop.
Tauri Integration: Leverage Tauri for lightweight, native desktop application capabilities.
Comprehensive Workflow: Follow a systematic process from setting up your development environment to deployment.

Introduction

Building a desktop application with Expo and Tauri enables you to use a common codebase for mobile and web apps while extending functionality to the desktop environment. Expo, well known for React Native mobile/web development, manages most of the UI elements and shared logic, and Tauri capitalizes on web technologies to build efficient and secure desktop binaries. This guide will walk you through the full process of setting up an Expo project, integrating Tauri, configuring the environment, and handling platform-specific customizations.

Prerequisites & Setup

Prerequisites

Before beginning, ensure you have installed the following prerequisites:

Node.js (version 16 or higher) – available at nodejs.org.
npm or yarn package manager.
Expo CLI – install with npm install -g expo-cli or using Yarn.
Tauri CLI – requires Rust (version 1.64 or higher) installed on your system. Install Rust via rust-lang.org and then install Tauri CLI using cargo install tauri-cli from your terminal.
Python (version 3.7 or higher) for Tauri-related tooling.

Development Environment

Confirm all prerequisites are installed on your system. Use the following commands in your terminal to verify installations:


# Verify Node.js version
node -v

# Verify npm version
npm -v

# Check for Rust
rustc --version

# Install Tauri CLI
cargo install tauri-cli

Step 1: Creating a New Expo Project

Initialize the Project

Start by creating a new Expo project. Expo greatly simplifies the process of setting up a React Native application that works on both mobile and web platforms. Open your terminal and execute:


npx create-expo-app my-desktop-app

This command scaffolds a new Expo project named my-desktop-app. Change into the project directory:


cd my-desktop-app

Starting the Development Server

Once your project is initialized, start the Expo development server to verify that your project is operational:


npm start

This command also allows you to run the application on web, Android, or iOS simulators. In our case, we are primarily going to use the web build for the desktop application.

Step 2: Integrating Tauri with the Expo Project

Initialize Tauri

Tauri provides a structure to wrap your web build in a desktop application shell. In the root of your Expo project, initialize Tauri with the following command:


npx tauri init

Tauri will create a new directory called src-tauri that contains configuration files and code specific to building the desktop executable.

Configuring Tauri

The main configuration file for Tauri is tauri.conf.json or tauri.conf.ts, located inside the src-tauri directory. Customize this file to include your desired settings such as application name, version, and window configuration. Configure the distDir parameter to point to the Expo web build directory (for example, ./web-build).

Here is an example snippet for tauri.conf.json:


{
  "build": {
    "distDir": "../web-build",
    "devPath": "http://localhost:19006"
  },
  "tauri": {
    "windows": [
      {
        "title": "My Desktop App",
        "width": 800,
        "height": 600
      }
    ]
  }
}

More details can be found in Tauri’s official guide at Tauri Guide.

Step 3: Preparing the Web Build for Desktop

Utilizing Expo’s Web Bundle

To integrate with Tauri, you need to produce the web version of your Expo application. Ensure that your project is set up to use web-specific configurations if you plan on having desktop-specific behaviors.

When ready, generate the web build by running:


expo build:web

This command will bundle your Expo project into a web-optimized version, which is then served in the desktop window via Tauri.

Step 4: Running and Testing the Desktop Application

Development Mode

During development, it is best to run both the Expo web server and the Tauri development server simultaneously. First, start the Expo web server:


npm start --web

With the Expo server running, open a new terminal window and initiate the Tauri development mode:


npx tauri dev

This setup allows Tauri to load the Expo web bundle directly from the development server. As you make changes in your React Native components, they get reflected instantaneously in the Tauri wrapped window.

Production Build

When you are ready to distribute your desktop app, compile and package the final executable. Build the Expo web bundle:


expo build:web

Then, package the Tauri desktop application using:


npm run tauri build

The above command produces binaries for Windows, macOS, or Linux (depending on your host system), typically located in the src-tauri/target/release directory.

Step 5: Handling Platform-Specific Code

Shared and Conditional Components

A unified codebase is a strong benefit of using Expo. However, desktop environments may require some adjustments. Utilize React Native’s built-in Platform module to execute conditional code based on the target platform:


// Example: Conditional logic for platform-specific features
import { Platform } from 'react-native';

if (Platform.OS === 'web') {
  // Implement logic that may differ on the desktop version
  // You can interface with Tauri’s APIs here if needed
} else {
  // Mobile-specific code
}

Custom hooks or context modules can also be set up to abstract away platform-specific implementations. This encourages code reuse while allowing for necessary desktop-specific optimizations.

Integration with Tauri APIs

Tauri provides APIs that allow your application to access native functionalities, such as file system access, window manipulation, and inter-process communication. Ensure your application leverages these for desktop-specific interactions. Here’s a brief example for invoking a Tauri command:


// In your JavaScript code within the Expo project
import { invoke } from '@tauri-apps/api/tauri';

async function readFile() {
  try {
    const fileContent = await invoke('read_file', { path: '/path/to/file' });
    console.log(fileContent);
  } catch (error) {
    console.error('Error reading file:', error);
  }
}

This allows your app to call Rust commands defined in the Tauri backend, which can be further customized as needed.

Step 6: Directory Structure and Workflow Management

Monorepo and Code Sharing

For larger projects where maintaining separate codebases for mobile, web, and desktop might become cumbersome, it is highly recommended to adopt a monorepo structure. Tools such as Yarn Workspaces help manage shared business logic, UI components, and services efficiently. A typical project structure might look like:

Directory	Description
/apps/mobile	Expo project for mobile development
/apps/web	Web build of the Expo project
/apps/desktop	Tauri integration for desktop app
/packages/ui	Reusable UI components shared across platforms
/packages/business-logic	Shared data models and services

This structure ensures that updates to shared code are reflected instantly across all platforms.

Step 7: Practical Example and Walkthrough

Building a Simple Desktop Application

Let’s combine the steps into a practical example. Suppose you want to build a desktop application that displays a simple interface with a welcome message. First, create your Expo project as detailed, then configure Tauri to wrap the web build.

In the App.js file of your Expo project, insert:


import React from 'react';
import { View, Text, StyleSheet } from 'react-native';

export default function App() {
  return (
    <View style={styles.container}>
      <Text style={styles.welcome}>Welcome to My Desktop App!</Text>
    </View>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center'
  },
  welcome: {
    fontSize: 24,
    fontWeight: 'bold'
  }
});

Next, ensure Tauri is configured with your web build directory as shown earlier while initializing it with npx tauri init.

Run your Expo web server:


npm start --web

Then, in another terminal instance, run Tauri in development mode:


npx tauri dev

Upon making desired changes and verifying functionality in development, build your desktop app using:


npm run tauri build

This command packages your application into a native desktop executable.

Additional Considerations

Performance Optimization

While Tauri apps are known for their efficiency compared to other frameworks like Electron, keep the following in mind:

Minimize modifications to the default configuration unless necessary.
Leverage Expo's performance profiling tools to optimize your JavaScript code.
When integrating Tauri, consider using lazy-loading for heavy desktop-specific modules.

Security Measures

Tauri emphasizes security by minimizing the attack surface with Rust-based backend logic. However, always validate data coming from frontend inputs and use secure APIs provided by Tauri for desktop integrations.

Debugging and Troubleshooting

Use your browser’s developer console to debug the Expo web build. Tauri also produces logs that can be consulted using the terminal output during both development and production builds.