---

name: umbraco-example-generator description: Generate testable example extensions and run them in the Umbraco backoffice version: 1.0.0 location: managed allowed-tools: Read, Write, Edit, Glob, Grep, Bash

Umbraco Example Generator

Generate complete, testable example extensions for the Umbraco backoffice and run them using the Umbraco source's dev infrastructure.

When to Use

• Creating demonstration extensions
• Building testable extension examples
• Rapid development with hot reload
• Testing extensions without .NET backend

Related Skills

• umbraco-unit-testing - Add unit tests to examples
• umbraco-mocked-backoffice - E2E testing patterns
• umbraco-backoffice - Extension type blueprints

---

Quick Start

1. Clone Umbraco source (one-time setup)

Copygit clone https://github.com/umbraco/Umbraco-CMS
cd Umbraco-CMS/src/Umbraco.Web.UI.Client
npm install

2. Create your extension folder

Copymy-extension/
├── index.ts           # REQUIRED - exports manifests
└── my-element.ts      # Your element(s)

3. Create index.ts (exports manifests)

Copyimport './my-element.js';

export const manifests = [
  {
    type: 'dashboard',
    alias: 'My.Dashboard',
    name: 'My Dashboard',
    element: 'my-element',
    meta: { label: 'My Dashboard', pathname: 'my-dashboard' },
    conditions: [{ alias: 'Umb.Condition.SectionAlias', match: 'Umb.Section.Content' }]
  }
];

4. Create your element

Copy// my-element.ts
import { LitElement, html, customElement } from '@umbraco-cms/backoffice/external/lit';

@customElement('my-element')
export class MyElement extends LitElement {
  render() {
    return html`<uui-box headline="Hello">It works!</uui-box>`;
  }
}

5. Run it

Copycd Umbraco-CMS/src/Umbraco.Web.UI.Client
VITE_EXTERNAL_EXTENSION=/full/path/to/my-extension npm run dev:external

Open http://localhost:5173 - your extension appears in the Content section.

---

How It Works

The Umbraco source (Umbraco-CMS/src/Umbraco.Web.UI.Client) provides two ways to load extensions:

1. Internal Examples (npm run example)

Examples placed in the examples/ folder inside the Umbraco source.

Copycd Umbraco-CMS/src/Umbraco.Web.UI.Client
npm run example
# Select from list of examples

How it works: Sets VITE_EXAMPLE_PATH and imports ./examples/{name}/index.ts

2. External Extensions (npm run dev:external)

Extensions from any location on your filesystem - perfect for developing packages.

Copycd Umbraco-CMS/src/Umbraco.Web.UI.Client
VITE_EXTERNAL_EXTENSION=/path/to/your/extension npm run dev:external

How it works:

1. Sets VITE_UMBRACO_USE_MSW=on (mocked APIs)
2. Creates @external-extension alias pointing to your extension path
3. Imports @external-extension/index.ts and registers exports with umbExtensionsRegistry
4. Resolves @umbraco-cms/backoffice/* imports from the main project (avoids duplicate element registrations)

Extension Loading (index.ts)

Copy// From Umbraco-CMS/src/Umbraco.Web.UI.Client/index.ts
if (import.meta.env.VITE_EXTERNAL_EXTENSION) {
  const js = await import('@external-extension/index.ts');
  if (js) {
    Object.keys(js).forEach((key) => {
      const value = js[key];
      if (Array.isArray(value)) {
        umbExtensionsRegistry.registerMany(value);
      } else if (typeof value === 'object') {
        umbExtensionsRegistry.register(value);
      }
    });
  }
}

Key point: Your index.ts must export manifests (arrays or objects) that get registered automatically.

---

Setup

Prerequisites

Clone and set up the Umbraco source:

Copygit clone https://github.com/umbraco/Umbraco-CMS
cd Umbraco-CMS/src/Umbraco.Web.UI.Client
npm install

Extension Structure

Your extension needs this minimal structure:

Copymy-extension/
├── index.ts              # Exports manifests array (REQUIRED)
├── my-element.ts         # Your element(s)
├── my-context.ts         # Context (if needed)
├── package.json          # Optional - for IDE support and tests
├── tsconfig.json         # Optional - for IDE support
└── README.md             # Documentation

Required: index.ts

Your index.ts must export manifests that will be registered:

Copyimport './my-dashboard.element.js';

export const manifests = [
  {
    type: 'dashboard',
    alias: 'My.Dashboard',
    name: 'My Dashboard',
    element: 'my-dashboard',
    weight: 100,
    meta: {
      label: 'My Dashboard',
      pathname: 'my-dashboard'
    },
    conditions: [
      {
        alias: 'Umb.Condition.SectionAlias',
        match: 'Umb.Section.Content'
      }
    ]
  }
];

Optional: package.json (for IDE support)

Copy{
  "name": "my-extension",
  "type": "module",
  "devDependencies": {
    "@umbraco-cms/backoffice": "^17.0.0",
    "typescript": "~5.8.0"
  }
}

Important: The @umbraco-cms/backoffice dependency is only for IDE TypeScript support. At runtime, imports are resolved from the main Umbraco project.

---

Running Your Extension

Start the mocked backoffice

Copycd /path/to/Umbraco-CMS/src/Umbraco.Web.UI.Client
VITE_EXTERNAL_EXTENSION=/absolute/path/to/my-extension npm run dev:external

Open in browser

Navigate to http://localhost:5173 - your extension is loaded automatically.

Hot reload

Changes to your extension files trigger hot reload - no restart needed.

---

Patterns

Basic Element

Copy// my-dashboard.element.ts
import { LitElement, html, css, customElement } from '@umbraco-cms/backoffice/external/lit';

@customElement('my-dashboard')
export class MyDashboardElement extends LitElement {
  static override styles = css`
    :host {
      display: block;
      padding: var(--uui-size-layout-1);
    }
  `;

  override render() {
    return html`
      <uui-box headline="My Extension">
        <p>Running in the mocked backoffice!</p>
      </uui-box>
    `;
  }
}

declare global {
  interface HTMLElementTagNameMap {
    'my-dashboard': MyDashboardElement;
  }
}

Element with Context

Copyimport { html, customElement, state } from '@umbraco-cms/backoffice/external/lit';
import { UmbLitElement } from '@umbraco-cms/backoffice/lit-element';
import { EXAMPLE_MY_CONTEXT } from './my-context.js';

@customElement('example-my-feature-view')
export class ExampleMyFeatureViewElement extends UmbLitElement {
  @state()
  private _value?: string;

  constructor() {
    super();
    this.consumeContext(EXAMPLE_MY_CONTEXT, (context) => {
      this.observe(context.value, (value) => {
        this._value = value;
      });
    });
  }

  override render() {
    return html`
      <uui-box headline="My Feature Example">
        <p>Current value: ${this._value ?? 'Loading...'}</p>
      </uui-box>
    `;
  }
}

export default ExampleMyFeatureViewElement;

declare global {
  interface HTMLElementTagNameMap {
    'example-my-feature-view': ExampleMyFeatureViewElement;
  }
}

Context

Copyimport { UmbContextToken } from '@umbraco-cms/backoffice/context-api';
import { UmbContextBase } from '@umbraco-cms/backoffice/class-api';
import { UmbStringState } from '@umbraco-cms/backoffice/observable-api';
import type { UmbControllerHost } from '@umbraco-cms/backoffice/controller-api';

export class ExampleMyContext extends UmbContextBase {
  #value = new UmbStringState('initial');
  readonly value = this.#value.asObservable();

  constructor(host: UmbControllerHost) {
    super(host, EXAMPLE_MY_CONTEXT);
  }

  setValue(value: string) {
    this.#value.setValue(value);
  }

  getValue() {
    return this.#value.getValue();
  }

  public override destroy(): void {
    this.#value.destroy();
    super.destroy();
  }
}

export const EXAMPLE_MY_CONTEXT = new UmbContextToken<ExampleMyContext>(
  'ExampleMyContext'
);

export { ExampleMyContext as api };

---

Adding Tests

Unit Tests

Add unit tests using @open-wc/testing. See umbraco-unit-testing skill for full setup.

Copynpm install --save-dev @open-wc/testing @web/test-runner @web/test-runner-playwright

E2E Tests (Playwright)

Add E2E tests that run against the mocked backoffice. See umbraco-mocked-backoffice skill for patterns.

Copynpm install --save-dev @playwright/test
npx playwright install chromium

---

Examples

Reference Example

Location: ./examples/workspace-feature-toggle/

A complete standalone example demonstrating:

• Workspace context with UmbArrayState
• Workspace view consuming context
• Workspace action executing context methods
• Workspace footer app showing summary
• 38 unit tests + 13 E2E tests

Copycd examples/workspace-feature-toggle
npm install
npm test              # Unit tests
npm run test:e2e      # E2E tests (requires mocked backoffice running)

Official Umbraco Examples

Location: Umbraco-CMS/src/Umbraco.Web.UI.Client/examples/

27 official examples covering all extension types. Run any example:

Copycd Umbraco-CMS/src/Umbraco.Web.UI.Client
npm run example
# Select from list

---

Naming Conventions

---

Troubleshooting

Extension not appearing

1. Check index.ts exports a manifests array
2. Verify the path in VITE_EXTERNAL_EXTENSION is absolute
3. Check browser console for 📦 Loading external extension from: message
4. Ensure condition matches the section you're viewing

Import errors

Imports should use @umbraco-cms/backoffice/*. The Vite plugin resolves these from the main project.

"CustomElementRegistry" already defined

Your extension's node_modules is being used instead of the main project's. The external-extension-resolver plugin should handle this, but ensure:

• You're using npm run dev:external
• Imports use @umbraco-cms/backoffice/* not relative paths to node_modules

Changes not hot reloading

Ensure the file is within the path specified by VITE_EXTERNAL_EXTENSION. Only files in that directory tree are watched.