Routing Errors

Routing Errors Overview

Routing Errors is a building block you will reach for often in single-spa. It keeps related logic together and makes your intent obvious to reviewers and future maintainers.

When you learn routing errors properly, you avoid the guesswork that leads to bugs and rework. The example below shows the shape you will use in most real single-spa projects.

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

activeWhen decides which route ranges a micro frontend owns.

Routing Errors Example

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

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

Single-SPA Cheatsheet

Core single-spa APIs related to routing errors.

How Routing Errors Works in Single-SPA

Routing Errors 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 Routing Errors

For reliable micro frontends, routing errors 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

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

Key Takeaways

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