What Is Single-SPA?

In this lesson you will learn what is single-spa? in single-spa, why it matters within single-spa basics, and how to use it correctly with clear, copy-ready examples.

What Is Single-SPA? Overview

What Is Single-SPA? 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 what is single-spa? 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.

import { registerApplication, start } from 'single-spa';

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

start();

single-spa orchestrates multiple framework apps on one page through a root config.

What Is Single-SPA? Example

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

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

Single-SPA Cheatsheet

Core single-spa APIs related to what is single-spa?.

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 What Is Single-SPA? Works in Single-SPA

What Is Single-SPA? 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.

single-spa orchestrates multiple framework apps on one page through a root config.

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 What Is Single-SPA?

For reliable micro frontends, what is single-spa? 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

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

Key Takeaways

What Is Single-SPA? is a core part of working effectively with single-spa.
Start small and keep what is single-spa? focused on a single responsibility.
Apply consistent patterns so what is single-spa? scales across your project.
Test and document what is single-spa? to keep it maintainable over time.

Pro Tip

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