Fix “React-Refresh/Runtime.js: WebSocket Connection Failed” Error

While working on a React project, I encountered the "React-Refresh/Runtime.js: WebSocket connection failed" error. This happened when I was using React Fast Refresh, a feature that allows components to update without losing their state during development. The error appeared in the browser console, and my app stopped hot-reloading, which slowed down my workflow.

The issue seemed to occur after I made changes to my Webpack configuration. I noticed that the WebSocket, which is used for communication between the browser and the development server, failed to connect. This broke the hot-reloading feature, forcing me to manually refresh the browser every time I made a change. It was frustrating, but I managed to resolve it by following a few steps.

What Causes the “React-Refresh/Runtime.js: WebSocket Connection Failed” Error?

The error typically occurs when the WebSocket connection between the React development server and the browser fails. This can happen due to several reasons, such as incorrect Webpack settings, network issues, or misconfigured environment variables. The WebSocket is crucial for React Fast Refresh, as it enables real-time updates during development.

Another common cause is using an outdated version of React or related tools. Sometimes, third-party plugins or extensions in the browser can also interfere with the WebSocket connection. Identifying the root cause is the first step toward fixing the issue.

Step-by-Step Guide to Fix the Error

Check Your Webpack Configuration

The first thing I did was review my Webpack configuration. I ensured that the webpack-dev-server was set up correctly. The hot option must be enabled for React Fast Refresh to work. Here’s an example of how to configure it:

module.exports = {
  // Other configurations...
  devServer: {
    hot: true,
  },
};

If the hot option is missing or set to false, the WebSocket connection will fail. Double-check your configuration and restart the development server after making changes.

Verify React and React-DOM Versions

I realized that my project was using an older version of React and React-DOM. React Fast Refresh requires React 16.9 or higher. To update, I ran the following commands:

npm install react@latest react-dom@latest

After updating, I restarted the development server. This resolved compatibility issues and allowed the WebSocket to connect successfully.

Clear Browser Cache and Disable Extensions

Sometimes, browser cache or extensions can block the WebSocket connection. I cleared my browser cache and disabled extensions like ad blockers, which might interfere with the connection. This simple step can often fix the issue without any code changes.

Check Network Settings

If you’re working in a restricted network environment, firewalls or proxies might block the WebSocket connection. I checked my network settings and ensured that the required ports were open. You can also try switching to a different network to see if the issue persists.

Reinstall Node Modules

Corrupted or missing node modules can also cause the error. I deleted the node_modules folder and the package-lock.json file, then reinstalled the dependencies using:

npm install

This ensured that all dependencies were correctly installed and up to date.

Use Environment Variables

If you’re using environment variables, ensure they are correctly configured. For example, set FAST_REFRESH to true in your .env file:

FAST_REFRESH=true

This ensures that React Fast Refresh is enabled in your development environment.

Tips to Prevent the Error in the Future

Keep Your Tools Updated

Always use the latest versions of React, Webpack, and related tools. Regular updates fix bugs and improve compatibility, reducing the chances of encountering errors like this.

Test After Configuration Changes

Whenever you modify your Webpack or environment settings, test the application immediately. This helps you catch and fix issues before they disrupt your workflow.

Monitor Browser Console Logs

The browser console provides valuable insights into errors and warnings. Regularly check the console to identify and resolve issues early.

Final Thoughts

Fixing the “React-Refresh/Runtime.js: WebSocket connection failed” error can be challenging, but it’s manageable with the right approach. By following the steps above, I was able to resolve the issue and restore hot-reloading in my React project. Remember to keep your tools updated, review your configurations, and test your application regularly to avoid similar problems in the future.