"Invalid options object" Error with Proxy in React Dev Server

When setting up a React application with a proxy server, you might encounter the error:

Invalid options object. Dev Server has been initialized using an options object that does not match the API schema.
- options.allowedHosts[0] should be a non-empty string.

This typically occurs when adding a proxy configuration to your package.json file.

Root Cause

The issue stems from a compatibility problem between newer versions of Node.js and the react-scripts development server. Specifically:

• Node.js v18+ compatibility: The Node v18 update changed how os.networkInterfaces() returns network family information, breaking compatibility with older versions of react-scripts
• IP address detection: The development server's network detection logic fails to properly identify private IP addresses under certain conditions
• Proxy configuration: Adding a proxy triggers additional security checks that can fail with improper network configurations

Solutions

1. Environment Variable Workaround (Quick Fix)

Add the following to a .env file in your project root:

DANGEROUSLY_DISABLE_HOST_CHECK=true

Security Note

This disables an important security check. Only use this during development and never in production.

2. Manual Proxy Setup (Recommended)

Remove the proxy from package.json and set up a manual proxy configuration:

1. Install the required package:

   npm install http-proxy-middleware --save

2. Create src/setupProxy.js with the following content:

   const { createProxyMiddleware } = require('http-proxy-middleware');
   
   module.exports = function(app) {
     app.use(
       '/api',
       createProxyMiddleware({
         target: 'http://localhost:6000',
         changeOrigin: true,
       })
     );
   };

3. Node.js Version Management

If you're using Node.js v18 or newer, downgrading to a compatible version may resolve the issue:

# Using n version manager
sudo n 16.15.0

# Or using nvm
nvm install 16.15.0
nvm use 16.15.0

TIP

Node.js 16 LTS is a stable choice that works well with most React development setups.

4. Network Configuration Issues

Some network configurations can trigger this error:

• VPN connections: Try disconnecting from VPN
• Enterprise networks: Corporate networks with specific configurations may interfere
• DHCP issues: Ensure your machine is properly obtaining a valid IP address

5. Clear Cache and Reinstall

Sometimes clearing the package cache and reinstalling dependencies helps:

# Remove node_modules and lock files
rm -rf node_modules package-lock.json

# Clear npm cache
npm cache clean --force

# Reinstall dependencies
npm install

6. Update React Scripts

Ensure you're using a compatible version of react-scripts. Check your package.json:

{
  "dependencies": {
    "react-scripts": "^5.0.1"
  }
}

INFO

Version 5.0.1 of react-scripts may have fixes for this issue compared to 5.0.0.

Understanding the Technical Details

The error occurs in the Webpack development server configuration. When you specify a proxy, React enables additional security checks that verify your host configuration. The problem arises when:

1. The development server attempts to detect your local network IP
2. Node.js v18+ returns network interface data in a different format
3. The IP detection logic fails, resulting in an undefined allowedHosts value
4. The configuration validation fails because it expects a non-empty string

Best Practices for Proxy Configuration

For modern React applications, consider these approaches:

Custom Webpack Configuration

If you've ejected or use react-app-rewired, configure the proxy in webpack.config.js:

module.exports = {
  devServer: {
    proxy: {
      '/api': {
        target: 'http://localhost:6000',
        changeOrigin: true,
        secure: false
      }
    },
    allowedHosts: ['localhost', '.localhost']
  }
};

Environment-Specific Configuration

Create different proxy settings for development and production:

// In your configuration
const proxyConfig = process.env.NODE_ENV === 'development' ? {
  target: 'http://localhost:6000',
  changeOrigin: true
} : {
  target: 'https://your-production-api.com',
  changeOrigin: true
};

When to Use Which Solution

Solution	Best For	Complexity
Environment variable	Quick development fixes	Low
Manual proxy setup	Production-ready solutions	Medium
Node version change	Legacy compatibility	Medium
Network troubleshooting	Corporate/VPN environments	Variable

Final Recommendation

For most users, the manual proxy setup (#2) provides the most reliable long-term solution while maintaining security best practices.

If you continue to experience issues, check the Create React App documentation for the latest guidance on proxy configuration.