Navigation Events

Understanding navigation events helps you work with single-spa confidently. Here you will learn the core ideas behind navigation events, see working code, and pick up best practices used on real teams.

Navigation Events Overview

Navigation Events 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 navigation events 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.

Navigation Events Example

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

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

Single-SPA Cheatsheet

Core single-spa APIs related to navigation events.

API	Example	Purpose
registerApplication	`registerApplication({ name, app, activeWhen })`	Register a micro frontend
activeWhen	`activeWhen: ['/checkout']`	Route ownership
start	`start()`	Begin routing
bootstrap	`export async function bootstrap()`	One-time setup
mount	`export async function mount(props)`	Render the app
unmount	`export async function unmount(props)`	Clean up the app
import map	`systemjs-importmap`	Locate app bundles

How Navigation Events Works in Single-SPA

Navigation Events 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 Navigation Events

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

Concern	Recommendation
Isolation	One app's crash should not break others
Shared state	Prefer shared utility modules over globals
Routing	Keep activeWhen rules explicit and non-overlapping
Deployment	Release via import-map updates per app

Common Mistakes

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

Key Takeaways

Navigation Events is a core part of working effectively with single-spa.
Start small and keep navigation events focused on a single responsibility.
Apply consistent patterns so navigation events scales across your project.
Test and document navigation events to keep it maintainable over time.

Pro Tip

Pair navigation events with automated tests from day one. It is far cheaper to catch single-spa regressions in CI than in production.