Share Scope

Share Scope 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.

Share Scope Overview

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

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.

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

Module Federation Cheatsheet

Key Module Federation settings related to share scope.

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 Share Scope Works in Module Federation

Share Scope 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 Share Scope

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

Key Takeaways

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

Pro Tip

Bookmark this share scope pattern and reuse it. Consistency across your Module Federation codebase is worth more than clever one-off solutions.