Module Federation Runtime API

Runtime API Overview

Runtime API 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 runtime api focused and predictable. Start from the minimal example here, then layer in only the complexity your feature actually needs.

async function loadRemote(url, scope, module) {
  await __webpack_init_sharing__('default');
  const container = await import(/* webpackIgnore: true */ url);
  await container.init(__webpack_share_scopes__.default);
  const factory = await container.get(module);
  return factory();
}

const ProductList = await loadRemote(
  'http://localhost:3001/remoteEntry.js', 'catalog', './ProductList');

Dynamic remotes are resolved at runtime, so you can add micro frontends without rebuilding the host.

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

Module Federation Cheatsheet

Key Module Federation settings related to runtime api.

How Runtime API Works in Module Federation

Runtime API 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.

Dynamic remotes are resolved at runtime, so you can add micro frontends without rebuilding the host.

• 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 Runtime API

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

Key Takeaways

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