ChromeDevtoolsRails

This gem provides a minimal Rails engine that automatically serves the Chrome DevTools workspace mapping file at:

/.well-known/appspecific/com.chrome.devtools.json

When Chrome accesses this file from your local development server, it enables automatic workspace folder mapping, allowing you to edit and save source files (JS, CSS, etc.) directly from Chrome DevTools into your local Rails project.

This engine is automatically mounted and only active in development mode.

⚠️ Rails 8.2+ ships this natively

As of Rails 8.2, Rails serves this endpoint itself through a built-in Rails::DevToolsController (rails/rails#56245). On Rails 8.2 or newer, uncomment the generated devtools route in config/routes.rb and you no longer need this gem.

This gem is still useful on Rails 8.0 and 8.1, which have no native support. When it detects Rails 8.2+, it keeps serving the endpoint but emits a deprecation warning so you know you can switch to the native controller and drop the dependency.

🚀 Usage

  1. Visit your Rails app on localhost.
  2. Open Chrome DevTools → Sources tab.
  3. Chrome will auto-detect the .well-known file and prompt to map your local project.
  4. Approve the mapping — changes made in DevTools will now be saved directly to disk.

🔧 Installation

Add this line to your application's Gemfile:

gem "chrome_devtools_rails"

Then run:

bundle install

No route configuration is needed — the engine mounts itself automatically in development.

✅ Requirements

  • Ruby ≥ 3.2
  • Rails ≥ 8.0.2
  • Google Chrome v89+ (with DevTools workspace support)

🤝 Contributing

Pull requests are welcome on GitHub at https://github.com/6temes/chrome_devtools_rails.

📄 License

This gem is open source and released under the MIT License.