Shared Dependencies

Shared Dependencies sits at the heart of shared dependencies in Module Federation. This guide walks through the concept step by step, with examples, a cheatsheet, and common mistakes to avoid.

Shared Dependencies Overview

Shared Dependencies 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 shared dependencies focused and predictable. Start from the minimal example here, then layer in only the complexity your feature actually needs.

new ModuleFederationPlugin({
  name: 'shell',
  shared: {
    react: { singleton: true, requiredVersion: '^18.2.0' },
    'react-dom': { singleton: true, requiredVersion: '^18.2.0' },
  },
});

Marking shared libraries as singletons ensures one React instance is used across all micro frontends.

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

Module Federation Cheatsheet

Key Module Federation settings related to shared dependencies.

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 Shared Dependencies Works in Module Federation

Shared Dependencies 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.

Marking shared libraries as singletons ensures one React instance is used across all micro frontends.

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 Shared Dependencies

In production, shared dependencies 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

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

Key Takeaways

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

Pro Tip

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