Micro Frontends

Micro Frontends Overview

At its core, micro frontends 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 micro frontends pays off across the whole codebase: fewer surprises, easier testing, and smoother onboarding. The snippet below is a solid starting point.

const { ModuleFederationPlugin } = require('webpack').container;

module.exports = {
  plugins: [
    new ModuleFederationPlugin({
      name: 'shell',
      remotes: { catalog: 'catalog@http://localhost:3001/remoteEntry.js' },
      exposes: {},
      shared: { react: { singleton: true }, 'react-dom': { singleton: true } },
    }),
  ],
};

ModuleFederationPlugin configures which modules an app exposes, consumes, and shares.

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

Module Federation Cheatsheet

Key Module Federation settings related to micro frontends.

How Micro Frontends Works in Module Federation

Micro Frontends 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.

ModuleFederationPlugin configures which modules an app exposes, consumes, and shares.

• 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 Micro Frontends

In production, micro frontends 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 micro frontends.
• Leaving micro frontends untested, so regressions slip into production.
• Over-engineering micro frontends before you actually need the extra flexibility.
• Ignoring documentation, which makes micro frontends hard for the next developer to change.

Key Takeaways

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