Nested Routes

Nested Routes Overview

At its core, nested routes is about doing one thing well inside your single-spa project. Once you understand the pattern, you can apply it consistently across features and teams.

Good nested routes pays off across the whole codebase: fewer surprises, easier testing, and smoother onboarding. The snippet below is a solid starting point.

registerApplication({
  name: '@org/checkout',
  app: () => System.import('@org/checkout'),
  activeWhen: (location) => location.pathname.startsWith('/checkout'),
});

activeWhen decides which route ranges a micro frontend owns.

Nested Routes Example

registerApplication({
  name: '@org/app',
  app: () => System.import('@org/app'),
  activeWhen: ['/app'],
});
start();

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

Single-SPA Cheatsheet

Core single-spa APIs related to nested routes.

How Nested Routes Works in Single-SPA

Nested Routes is part of how single-spa lets multiple applications — even in different frameworks — coexist on one page. A root config registers each app and controls when it is active.

activeWhen decides which route ranges a micro frontend owns.

• A root config registers apps and calls start().
• Each app exports bootstrap, mount, and unmount lifecycles.
• activeWhen decides which routes each app owns.
• Import maps resolve each app's bundle at runtime.

Practical Guidance for Nested Routes

For reliable micro frontends, nested routes should isolate failures and keep shared state minimal. Let each team own its app end to end while agreeing on a few shared contracts.

Common Mistakes

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

Key Takeaways

• Nested Routes is a core part of working effectively with single-spa.
• Start small and keep nested routes focused on a single responsibility.
• Apply consistent patterns so nested routes scales across your project.
• Test and document nested routes to keep it maintainable over time.