---
title: Storybook for SvelteKit
sidebar:
  order: 6
  title: SvelteKit
---

Storybook for SvelteKit is a [framework](../../contribute/framework.mdx) that makes it easy to develop and test UI components in isolation for [SvelteKit](https://kit.svelte.dev/) applications. It includes:

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

<If notRenderer="svelte">
  <Callout variant="info">
    Storybook for SvelteKit is only supported in [Svelte](?renderer=svelte) projects.
  </Callout>

  {/* End non-supported renderers */}
</If>

<If renderer="svelte">
  ## 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:

  {/* prettier-ignore-start */}

  <CodeSnippets path="init-command.md" />

  {/* prettier-ignore-end */}

  [More on getting started with Storybook.](../install.mdx)

  ### 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:

  {/* prettier-ignore-start */}

  <CodeSnippets path="storybook-upgrade.md" />

  {/* prettier-ignore-end */}

  #### 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:

  {/* prettier-ignore-start */}

  <CodeSnippets path="sveltekit-install.md" />

  {/* prettier-ignore-end */}

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

  {/* prettier-ignore-start */}

  <CodeSnippets path="sveltekit-add-framework.md" />

  {/* prettier-ignore-end */}

  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](https://kit.svelte.dev/docs/modules) that aren't supported. Here's a breakdown of what will and will not work within Storybook:

  | Module                                                                             | Status                 | Note                                                                                                                                    |
  | ---------------------------------------------------------------------------------- | ---------------------- | --------------------------------------------------------------------------------------------------------------------------------------- |
  | [`$app/environment`](https://kit.svelte.dev/docs/modules#$app-environment)         | ✅ Supported           | `version` is always empty in Storybook.                                                                                                 |
  | [`$app/forms`](https://kit.svelte.dev/docs/modules#$app-forms)                     | ⚠️ **Experimental**     | See [How to mock](#how-to-mock).                                                                                                        |
  | [`$app/navigation`](https://kit.svelte.dev/docs/modules#$app-navigation)           | ⚠️ **Experimental**     | See [How to mock](#how-to-mock).                                                                                                        |
  | [`$app/paths`](https://kit.svelte.dev/docs/modules#$app-paths)                     | ✅ Supported           | Requires SvelteKit 1.4.0 or newer.                                                                                                      |
  | [`$app/stores`](https://kit.svelte.dev/docs/modules#$app-stores)                   | ⚠️ **Experimental**     | See [How to mock](#how-to-mock).                                                                                                        |
  | [`$env/dynamic/public`](https://kit.svelte.dev/docs/modules#$env-dynamic-public)   | 🚧 Partially supported | Only supported in development mode. Storybook is built as a static app with no server-side API, so it cannot dynamically serve content. |
  | [`$env/static/public`](https://kit.svelte.dev/docs/modules#$env-static-public)     | ✅ Supported           |                                                                                                                                         |
  | [`$lib`](https://kit.svelte.dev/docs/modules#$lib)                                 | ✅ Supported           |                                                                                                                                         |
  | [`@sveltejs/kit/*`](https://kit.svelte.dev/docs/modules#sveltejs-kit)              | ✅ Supported           |                                                                                                                                         |
  | [`$env/dynamic/private`](https://kit.svelte.dev/docs/modules#$env-dynamic-private) | ⛔ Not supported       | This is a server-side feature, and Storybook renders all components on the client.                                                      |
  | [`$env/static/private`](https://kit.svelte.dev/docs/modules#$env-static-private)   | ⛔ Not supported       | This is a server-side feature, and Storybook renders all components on the client.                                                      |
  | [`$service-worker`](https://kit.svelte.dev/docs/modules#$service-worker)           | ⛔ Not supported       | This is a service worker feature, which does not apply to Storybook.                                                                    |

  ## How to mock

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

  ```ts title="MyComponent.stories.js|ts"
  export const MyStory = {
    parameters: {
      sveltekit_experimental: {
        stores: {
          page: {
            data: {
              test: 'passed',
            },
          },
          navigating: {
            route: {
              id: '/storybook',
            },
          },
          updated: true,
        },
      },
    },
  };
  ```

  The [available parameters](#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](../../essentials/actions.mdx).

  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:

  ```ts title="MyComponent.stories.js|ts"
  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](#hrefs) for more information.

  ## Writing native Svelte stories

  Storybook provides a Svelte [addon](https://storybook.js.org/addons/@storybook/addon-svelte-csf) maintained by the community, enabling you to write stories for your Svelte components using the template syntax. 
  
  <Callout variant="info">
      The community actively maintains the Svelte CSF addon but still lacks some features currently available in the official Storybook Svelte framework support. For more information, see the [addon's documentation](https://github.com/storybookjs/addon-svelte-csf).
  </Callout>

  ### 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](#automatic-migration) from a previous version, you'll need to take additional steps to enable this feature.

  Run the following command to install the addon.

  {/* prettier-ignore-start */}

  <CodeSnippets path="svelte-csf-addon-install.md" />

  {/* prettier-ignore-end */}

  <Callout variant="info">
  
    The CLI's [`add`](../../api/cli-options.mdx#add) command automates the addon's installation and setup. To install it manually, see our [documentation](../addons/install-addons.mdx#manual-installation) on how to install addons.
  
  </Callout>

  Update your Storybook configuration file (i.e., `.storybook/main.js|ts`) to enable support for this format.
  
  {/* prettier-ignore-start */}

  <CodeSnippets path="main-config-svelte-csf-register.md" />

  {/* prettier-ignore-end */}

  ### Configure
 
  By default, the Svelte [addon](https://storybook.js.org/addons/@storybook/addon-svelte-csf) 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.

  {/* prettier-ignore-start */}

  <CodeSnippets path="svelte-csf-addon-options.md" />

  {/* prettier-ignore-end */}

  | Options          | Description |
  | ---------------- | ------------------------------------------------------------------------------------------------------------------ |
  | `legacyTemplate` | Enables support for the `Template` component for backward compatibility. <br/> `options: { legacyTemplate: true }` |
  
  <Callout variant="info">

    Enabling the `legacyTemplate` option can introduce a performance overhead and should be used cautiously. For more information, refer to the [addon's documentation](https://github.com/storybookjs/addon-svelte-csf/blob/next/README.md#legacy-api).
  
  </Callout>

  ### 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](../../writing-stories/parameters.mdx)), 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.
  
  {/* prettier-ignore-start */ }

  <CodeSnippets path="svelte-csf-story-migration.md" />

  {/* prettier-ignore-end */}

  #### 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.
  
  {/* prettier-ignore-start */ }

  <CodeSnippets path="svelte-csf-story-custom-children.md" />

  {/* prettier-ignore-end */}

  <Callout variant="info">

    If you need support for the `Template` component, the addon provides a feature flag for backward compatibility. For more information, see the [configuration options](#configure).
  
  </Callout>

  #### Story slots to snippets
  
  With Svelte's slot deprecation and the introduction of reusable [`snippets`](https://svelte.dev/docs/svelte/v5-migration-guide#Snippets-instead-of-slots), 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.

  ```svelte title="MyComponent.stories.svelte"
  <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`](../../writing-stories/tags.mdx). This property allows you to categorize and filter stories based on specific criteria and generate documentation based on the tags applied to the stories.
  
  {/* prettier-ignore-start */ }

  <CodeSnippets path="svelte-csf-addon-tags.md" />

  {/* prettier-ignore-end */}

  ## API

  ### Parameters

  This framework contributes the following [parameters](../../writing-stories/parameters.mdx) to Storybook, under the `sveltekit_experimental` namespace:

  #### `forms`

  Type: `{ enhance: () => void }`

  Provides mocks for the [`$app/forms`](https://kit.svelte.dev/docs/modules#$app-forms) module.

  ##### `forms.enhance`

  Type: `() => void`

  A callback that will be called when a form with [`use:enhance`](https://kit.svelte.dev/docs/form-actions#progressive-enhancement-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](../../essentials/actions.mdx). See [Mocking links](#mocking-links) for an example.

  #### `navigation`

  Type: See [SvelteKit docs](https://kit.svelte.dev/docs/modules#$app-navigation)

  Provides mocks for the [`$app/navigation`](https://kit.svelte.dev/docs/modules#$app-navigation) module.

  ##### `navigation.goto`

  Type: See [SvelteKit docs](https://kit.svelte.dev/docs/modules#$app-navigation-goto)

  A callback that will be called whenever [`goto`](https://kit.svelte.dev/docs/modules#$app-navigation-goto) is called. If no function is provided, an action will be logged to the [Actions panel](../../essentials/actions.mdx).

  ##### `navigation.pushState`

  Type: See [SvelteKit docs](https://kit.svelte.dev/docs/modules#$app-navigation-pushstate)

  A callback that will be called whenever [`pushState`](https://kit.svelte.dev/docs/modules#$app-navigation-pushstate) is called. If no function is provided, an action will be logged to the [Actions panel](../../essentials/actions.mdx).

  ##### `navigation.replaceState`

  Type: See [SvelteKit docs](https://kit.svelte.dev/docs/modules#$app-navigation-replacestate)

  A callback that will be called whenever [`replaceState`](https://kit.svelte.dev/docs/modules#$app-navigation-replacestate) is called. If no function is provided, an action will be logged to the [Actions panel](../../essentials/actions.mdx).

  ##### `navigation.invalidate`

  Type: See [SvelteKit docs](https://kit.svelte.dev/docs/modules#$app-navigation-invalidate)

  A callback that will be called whenever [`invalidate`](https://kit.svelte.dev/docs/modules#$app-navigation-invalidate) is called. If no function is provided, an action will be logged to the [Actions panel](../../essentials/actions.mdx).

  ##### `navigation.invalidateAll`

  Type: See [SvelteKit docs](https://kit.svelte.dev/docs/modules#$app-navigation-invalidateall)

  A callback that will be called whenever [`invalidateAll`](https://kit.svelte.dev/docs/modules#$app-navigation-invalidateall) is called. If no function is provided, an action will be logged to the [Actions panel](../../essentials/actions.mdx).

  ##### `navigation.afterNavigate`

  Type: See [SvelteKit docs](https://kit.svelte.dev/docs/modules#$app-navigation-afternavigate)

  An object that will be passed to the [`afterNavigate`](https://kit.svelte.dev/docs/modules#$app-navigation-afternavigate) function, which will be invoked when the `onMount` event fires.

  #### `stores`

  Type: See [SvelteKit docs](https://kit.svelte.dev/docs/modules#$app-stores)

  Provides mocks for the [`$app/stores`](https://kit.svelte.dev/docs/modules#$app-stores) module.

  ##### `stores.navigating`

  Type: See [SvelteKit docs](https://kit.svelte.dev/docs/modules#$app-stores-navigating)

  A partial version of the [`navigating`](https://kit.svelte.dev/docs/modules#$app-stores-navigating) store.

  ##### `stores.page`

  Type: See [SvelteKit docs](https://kit.svelte.dev/docs/modules#$app-stores-page)

  A partial version of the [`page`](https://kit.svelte.dev/docs/modules#$app-stores-page) store.

  ##### `stores.updated`

  Type: boolean

  A boolean representing the value of [`updated`](https://kit.svelte.dev/docs/modules#$app-stores-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:

  {/* prettier-ignore-start */ }

  <CodeSnippets path="sveltekit-framework-options.md" />

  {/* prettier-ignore-end */}

  The available options are:

  #### `builder`

  Type: `Record<string, any>`

  Configure options for the [framework's builder](../../api/main-config/main-config-framework.mdx#optionsbuilder). For Sveltekit, available options can be found in the [Vite builder docs](../../builders/vite.mdx).

  ## Troubleshooting

  ### Error when starting Storybook

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

  ```sh
  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.

  {/* End supported renderers */}
</If>
