Shared Design Tokens

In this lesson you will learn shared design tokens in single-spa, why it matters within design systems, and how to use it correctly with clear, copy-ready examples.

Shared Design Tokens Overview

Shared Design Tokens lets you structure single-spa 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 shared design tokens focused and predictable. Start from the minimal example here, then layer in only the complexity your feature actually needs.

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.

Shared Design Tokens Example

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

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

Single-SPA Cheatsheet

Core single-spa APIs related to shared design tokens.

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 Shared Design Tokens Works in Single-SPA

Shared Design Tokens 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 Shared Design Tokens

For reliable micro frontends, shared design tokens 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 shared design tokens snippets without understanding what each line does.
Skipping error handling and edge cases when wiring up shared design tokens.
Leaving shared design tokens untested, so regressions slip into production.
Over-engineering shared design tokens before you actually need the extra flexibility.

Key Takeaways

Shared Design Tokens is a core part of working effectively with single-spa.
Start small and keep shared design tokens focused on a single responsibility.
Apply consistent patterns so shared design tokens scales across your project.
Test and document shared design tokens to keep it maintainable over time.

Pro Tip

When you get stuck on shared design tokens, reduce it to the smallest reproducible example first — most single-spa issues become obvious once the noise is gone.