Lazy Loading

Lazy Loading is an important part of building production-ready Module Federation systems. This lesson explains what lazy loading means, how it works, and how to apply it with practical examples you can reuse.

Lazy Loading Overview

Lazy Loading lets you structure Module Federation work so it stays readable, testable, and easy to scale. Instead of ad-hoc code, you follow a clear pattern that other developers can recognise immediately.

The key is to keep lazy loading focused and predictable. Start from the minimal example here, then layer in only the complexity your feature actually needs.

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.

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

Module Federation Cheatsheet

Key Module Federation settings related to lazy loading.

Option	Example	Purpose
name	`name: 'shell'`	Unique container name
filename	`filename: 'remoteEntry.js'`	Remote entry manifest
exposes	`exposes: { './X': './src/X' }`	Modules a remote shares
remotes	`remotes: { app: 'app@url' }`	Remotes a host consumes
shared	`shared: { react: { singleton: true } }`	Deduplicate libraries
lazy load	`import('remote/Module')`	Load remotes on demand
Suspense	`<Suspense fallback={...}>`	Handle async loading

How Lazy Loading Works in Module Federation

Lazy Loading 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 Lazy Loading

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

Concern	Recommendation
Shared versions	Use singletons with requiredVersion
Runtime errors	Wrap remotes in error boundaries and fallbacks
Deployment	Resolve remotes from a runtime manifest
Performance	Lazy-load remotes and cache remoteEntry.js

Common Mistakes

Copying lazy loading snippets without understanding what each line does.
Skipping error handling and edge cases when wiring up lazy loading.
Leaving lazy loading untested, so regressions slip into production.
Over-engineering lazy loading before you actually need the extra flexibility.

Key Takeaways

Lazy Loading is a core part of working effectively with Module Federation.
Start small and keep lazy loading focused on a single responsibility.
Apply consistent patterns so lazy loading scales across your project.
Test and document lazy loading to keep it maintainable over time.

Pro Tip

When you get stuck on lazy loading, reduce it to the smallest reproducible example first — most Module Federation issues become obvious once the noise is gone.