Storybook for SvelteKit

Storybook for SvelteKit is a framework that makes it easy to develop and test UI components in isolation for SvelteKit applications. It includes:

• 🪄 Zero config
• 🧩 Easily mock many Kit modules
• 🔗 Automatic link handling
• 💫 and more!

Requirements

• SvelteKit ≥ 1.0
• Storybook ≥ 8.0

Getting started

In a project without Storybook

Follow the prompts after running this command in your Sveltekit project's root directory:

npm create storybook@latest

More on getting started with Storybook.

In a project with Storybook

This framework is designed to work with Storybook 7+. If you’re not already using v7, upgrade with this command:

npx storybook@latest upgrade

Automatic migration

When running the upgrade command above, you should get a prompt asking you to migrate to @storybook/sveltekit, which should handle everything for you. In case that auto-migration does not work for your project, refer to the manual migration below.

Manual migration

First, install the framework:

npm install --save-dev @storybook/sveltekit

Then, update your .storybook/main.js|ts to change the framework property:

import { StorybookConfig } from '@storybook/sveltekit';
 
const config: StorybookConfig = {
  // ...
  framework: '@storybook/sveltekit', // 👈 Add this
  // svelteOptions: { ... }, 👈 Remove this
};
 
export default config;

Finally, these packages are now either obsolete or part of @storybook/sveltekit, so you no longer need to depend on them directly. You can remove them (npm uninstall, yarn remove, pnpm remove) from your project:

• @storybook/svelte-vite
• @storybook/svelte-webpack5
• storybook-builder-vite
• @storybook/builder-vite

Supported features

All Svelte language features are supported out of the box, as the Storybook framework uses the Svelte compiler directly. However, SvelteKit has some Kit-specific modules that aren't supported. Here's a breakdown of what will and will not work within Storybook:

How to mock

To mock a SvelteKit import you can define it within parameters.sveltekit_experimental:

export const MyStory = {
  parameters: {
    sveltekit_experimental: {
      stores: {
        page: {
          data: {
            test: 'passed',
          },
        },
        navigating: {
          route: {
            id: '/storybook',
          },
        },
        updated: true,
      },
    },
  },
};

The available parameters are documented in the API section, below.

Mocking links

The default link-handling behavior (e.g., when clicking an <a href="..." /> element) is to log an action to the Actions panel.

You can override this by assigning an object to parameters.sveltekit_experimental.hrefs, where the keys are strings representing an href, and the values define your mock. For example:

export const MyStory = {
  parameters: {
    sveltekit_experimental: {
      hrefs: {
        '/basic-href': (to, event) => {
          console.log(to, event);
        },
        '/root.*': {
          callback: (to, event) => {
            console.log(to, event);
          },
          asRegex: true,
        },
      },
    },
  },
};

See the API reference for more information.

Writing native Svelte stories

Storybook provides a Svelte addon maintained by the community, enabling you to write stories for your Svelte components using the template syntax.

Setup

If you initialized your project with the Sveltekit framework, the addon has already been installed and configured for you. However, if you're migrating from a previous version, you'll need to take additional steps to enable this feature.

Run the following command to install the addon.

npx storybook@latest add @storybook/addon-svelte-csf

Update your Storybook configuration file (i.e., .storybook/main.js|ts) to enable support for this format.

// Replace your-framework with the name of your Svelte framework
import type { StorybookConfig } from '@storybook/your-framework';
 
const config: StorybookConfig = {
  stories: ['../src/**/*.stories.@(js|jsx|ts|tsx|svelte)'],
  addons: [
    // Other Storybook addons
    '@storybook/addon-svelte-csf',
  ],
};
 
export default config;

Configure

By default, the Svelte addon addon offers zero-config support for Storybook's SvelteKit framework. However, you can extend your Storybook configuration file (i.e., .storybook/main.js|ts) and provide additional addon options. Listed below are the available options and examples of how to use them.

// Replace your-framework with the name of your Svelte framework
import type { StorybookConfig } from '@storybook/your-framework';
 
const config: StorybookConfig = {
  // Other configuration
  addons: [
    {
      name: '@storybook/addon-svelte-csf',
      options: {
        legacyTemplate: true, // Enables the legacy template syntax
      },
    },
  ],
};
export default config;

Upgrade to Svelte CSF addon v5

With the Svelte 5 release, Storybook's Svelte CSF addon has been updated to support the new features. This guide will help you migrate to the latest version of the addon. Below is an overview of the major changes in version 5.0 and the steps needed to upgrade your project.

Simplified story API

If you are using the Meta component or the meta named export to define the story's metadata (e.g., parameters), you'll need to update your stories to use the new defineMeta function. This function returns an object with the required information, including a Story component that you must use to define your component stories.

<script>
  import { Meta, Story } from '@storybook/addon-svelte-csf';
 
  import MyComponent from './MyComponent.svelte';
</script>
 
 
<Meta title="MyComponent" component={MyComponent} />
 
<Story name="Default" />

Story templates

If you used the Template component to control how the component renders in the Storybook, this feature was replaced with built-in children support in the Story component, enabling you to compose components and define the UI structure directly in the story.

<script>
  import { Meta, Template, Story } from '@storybook/addon-svelte-csf';
 
  import OuterComponent from './OuterComponent.svelte';
  import MyComponent from './MyComponent.svelte';
</script>
 
<Meta title="MyComponent" component={MyComponent} />
 
<Template let:args>
  <OuterComponent>
    <MyComponent />
  </OuterComponent>
</Template>
 
<Story name="Default" />

Story slots to snippets

With Svelte's slot deprecation and the introduction of reusable snippets, the addon also introduced support for this feature allowing you to extend the Story component and provide a custom snippet to provide dynamic content to your stories. This feature extends the built-in children support in the Story component, allowing you to create dynamic stories without losing reactivity.

<script>
  import { defineMeta } from '@storybook/addon-svelte-csf';
 
  import MyComponent from './MyComponent.svelte';
 
  const { Story } = defineMeta({
    component: MyComponent,
  });
</script>
 
<Story name="Default" args={{ exampleProperty: true }}>
  {#snippet children(args)}
    <MyComponent {...args}>Reactive component</MyComponent>
  {/snippet}
</Story>

Tags support

If you enabled automatic documentation generation with the autodocs story property, you must replace it with tags. This property allows you to categorize and filter stories based on specific criteria and generate documentation based on the tags applied to the stories.

<script>
  import { Meta, Template, Story } from '@storybook/addon-svelte-csf';
 
  import MyComponent from './MyComponent.svelte';
</script>
 
<Meta title="MyComponent" component={MyComponent} />
 
<Template let:args>
  <MyComponent {...args} />
</Template>
 
<Story name="Default" autodocs />

API

Parameters

This framework contributes the following parameters to Storybook, under the sveltekit_experimental namespace:

forms

Type: { enhance: () => void }

Provides mocks for the $app/forms module.

forms.enhance

Type: () => void

A callback that will be called when a form with use:enhance is submitted.

hrefs

Type: Record<[path: string], (to: string, event: MouseEvent) => void | { callback: (to: string, event: MouseEvent) => void, asRegex?: boolean }>

If you have an <a /> tag inside your code with the href attribute that matches one or more of the links defined (treated as regex based if the asRegex property is true) the corresponding callback will be called. If no matching hrefs are defined, an action will be logged to the Actions panel. See Mocking links for an example.

navigation

Type: See SvelteKit docs

Provides mocks for the $app/navigation module.

navigation.goto

Type: See SvelteKit docs

A callback that will be called whenever goto is called. If no function is provided, an action will be logged to the Actions panel.

navigation.pushState

Type: See SvelteKit docs

A callback that will be called whenever pushState is called. If no function is provided, an action will be logged to the Actions panel.

navigation.replaceState

Type: See SvelteKit docs

A callback that will be called whenever replaceState is called. If no function is provided, an action will be logged to the Actions panel.

navigation.invalidate

Type: See SvelteKit docs

A callback that will be called whenever invalidate is called. If no function is provided, an action will be logged to the Actions panel.

navigation.invalidateAll

Type: See SvelteKit docs

A callback that will be called whenever invalidateAll is called. If no function is provided, an action will be logged to the Actions panel.

navigation.afterNavigate

Type: See SvelteKit docs

An object that will be passed to the afterNavigate function, which will be invoked when the onMount event fires.

stores

Type: See SvelteKit docs

Provides mocks for the $app/stores module.

stores.navigating

Type: See SvelteKit docs

A partial version of the navigating store.

stores.page

Type: See SvelteKit docs

A partial version of the page store.

stores.updated

Type: boolean

A boolean representing the value of updated (you can also access updated.check() which will be a no-op).

Options

You can pass an options object for additional configuration if needed:

import { StorybookConfig } from '@storybook/sveltekit';
 
const config: StorybookConfig = {
  // ...
  framework: {
    name: '@storybook/sveltekit',
    options: {
      // ...
    },
  },
};
 
export default config;

The available options are:

builder

Type: Record<string, any>

Configure options for the framework's builder. For Sveltekit, available options can be found in the Vite builder docs.

Troubleshooting

Error when starting Storybook

When starting Storybook after upgrading to v7.0, it may quit with the following error:

ERR! SyntaxError: Identifier '__esbuild_register_import_meta_url__' has already been declared

This can occur when manually upgrading from 6.5 to 7.0. To resolve it, you'll need to remove the svelteOptions property in .storybook/main.js, as that is not supported (and no longer necessary) in Storybook 7+ with SvelteKit.