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How to install addons Create an addon
Storybook knobs for web-components based on custom-elements.json
npm install storybook-addon-web-components-knobs
Last updated over 2 years ago
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Part of Open Web Components: guides, tools and libraries for modern web development and web components

CircleCI BrowserStack Status Renovate enabled


  • Create API documentation/playground


npm i storybook-addon-web-components-knobs @storybook/addon-docs

Create API playground

::: tip You can find a more interactive version of this in the withWebComponentsKnobs docs. :::

Base on the data in custom-elements.json we can automatically generate knobs for your stories.

To enable this feature you will need to add an additional decorator.


import { withKnobs, withWebComponentsKnobs } from '@open-wc/demoing-storybook';

  decorators={[withKnobs, withWebComponentsKnobs]}
  parameters={{ component: 'demo-wc-card', options: { selectedPanel: 'storybookjs/knobs/panel' } }}

<Story name="Custom Header" height="220px">
    <demo-wc-card header="Harry Potter">A character that is part of a book series...</demo-wc-card>


import { html } from 'lit-html';
import { withKnobs, withWebComponentsKnobs } from '@open-wc/demoing-storybook';

import '../demo-wc-card.js';

export default {
  title: 'Card|Playground',
  component: 'demo-wc-card',
  decorators: [withKnobs, withWebComponentsKnobs],
  parameters: { options: { selectedPanel: 'storybookjs/knobs/panel' } },

export const singleComponent = () => html` <demo-wc-card></demo-wc-card> `;

For additional features like

  • define which components to show knobs for
  • showing knobs for multiple different components
  • syncing components states to knobs
  • Filtering properties and debugging states

please see the official documentation of the knobs for web components decorator.


In order to get documentation for web-components you will need to have a custom-elements.json file. You can hand write it or better generate it. Depending on the web components sugar you are choosing your mileage may vary. Please not that the details of the file are still being discussed so we may adopt to changes in custom-elements.json without a breaking release.

Known analyzers that output custom-elements.json:

It basically looks like this:

  "version": 2,
  "tags": [
      "name": "demo-wc-card",
      "properties": [
          "name": "header",
          "type": "String",
          "description": "Shown at the top of the card"
      "events": [],
      "slots": [],
      "cssProperties": []

For a full example see the ./demo/custom-elements.json.

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