Exposed Modules

Exposed Modules Overview

At its core, exposed modules is about doing one thing well inside your Module Federation project. Once you understand the pattern, you can apply it consistently across features and teams.

Good exposed modules pays off across the whole codebase: fewer surprises, easier testing, and smoother onboarding. The snippet below is a solid starting point.

// remote (webpack.config.js)
const { ModuleFederationPlugin } = require('webpack').container;

module.exports = {
  plugins: [
    new ModuleFederationPlugin({
      name: 'catalog',
      filename: 'remoteEntry.js',
      exposes: {
        './ProductList': './src/ProductList',
      },
      shared: ['react', 'react-dom'],
    }),
  ],
};

A remote exposes modules through remoteEntry.js so hosts can load them at runtime.

Exposed Modules Example

new ModuleFederationPlugin({
  name: 'app',
  filename: 'remoteEntry.js',
  exposes: { './Widget': './src/Widget' },
  remotes: { other: 'other@http://host/remoteEntry.js' },
  shared: { react: { singleton: true } },
});

• Start from a minimal Exposed Modules example and grow it only as needed.
• Keep configuration explicit so Exposed Modules behaves the same in every environment.
• Name things clearly so teammates understand your Exposed Modules at a glance.
• Add tests around Exposed Modules early to lock in expected behaviour.

Module Federation Cheatsheet

Key Module Federation settings related to exposed modules.

How Exposed Modules Works in Module Federation

Exposed Modules builds on Module Federation's ability to load code from another independently built and deployed application at runtime. Each app can be a host, a remote, or both.

A remote exposes modules through remoteEntry.js so hosts can load them at runtime.

• Remotes expose modules through a remoteEntry.js manifest.
• Hosts declare remotes and import exposed modules dynamically.
• Shared dependencies are deduplicated, ideally as singletons.
• Each micro frontend builds and deploys on its own schedule.

Practical Guidance for Exposed Modules

In production, exposed modules needs careful version management and graceful failure handling. Align shared dependency versions and always render a fallback when a remote cannot load.

Common Mistakes

• Skipping error handling and edge cases when wiring up exposed modules.
• Leaving exposed modules untested, so regressions slip into production.
• Over-engineering exposed modules before you actually need the extra flexibility.
• Ignoring documentation, which makes exposed modules hard for the next developer to change.

Key Takeaways

• Exposed Modules is a core part of working effectively with Module Federation.
• Start small and keep exposed modules focused on a single responsibility.
• Apply consistent patterns so exposed modules scales across your project.
• Test and document exposed modules to keep it maintainable over time.