URL-Based State

URL-Based State Overview

At its core, url-based state 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 url-based state 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.

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

Module Federation Cheatsheet

Key Module Federation settings related to url-based state.

How URL-Based State Works in Module Federation

URL-Based State 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 URL-Based State

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

Common Mistakes

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

Key Takeaways

• URL-Based State is a core part of working effectively with Module Federation.
• Start small and keep url-based state focused on a single responsibility.
• Apply consistent patterns so url-based state scales across your project.
• Test and document url-based state to keep it maintainable over time.