astro/packages/integrations/svelte/README.md

@astrojs/svelte 🧡

This Astro integration enables server-side rendering and client-side hydration for your Svelte components.

Installation

There are two ways to add integrations to your project. Let's try the most convenient option first!

astro add command

Astro includes a CLI tool for adding first party integrations: astro add. This command will:

1. (Optionally) Install all necessary dependencies and peer dependencies
2. (Also optionally) Update your astro.config.* file to apply this integration

To install @astrojs/svelte, run the following from your project directory and follow the prompts:

# Using NPM
npx astro add svelte
# Using Yarn
yarn astro add svelte
# Using PNPM
pnpm astro add svelte

If you run into any issues, feel free to report them to us on GitHub and try the manual installation steps below.

Install dependencies manually

First, install the @astrojs/svelte integration like so:

npm install @astrojs/svelte

Most package managers will install associated peer dependencies as well. Still, if you see a "Cannot find package 'svelte'" (or similar) warning when you start up Astro, you'll need to install Svelte:

npm install svelte

Now, apply this integration to your astro.config.* file using the integrations property:

astro.config.mjs

import svelte from '@astrojs/svelte';

export default {
  // ...
  integrations: [svelte()],
}

Getting started

To use your first Svelte component in Astro, head to our UI framework documentation. You'll explore:

• 📦 how framework components are loaded,
• 💧 client-side hydration options, and
• 🤝 opportunities to mix and nest frameworks together

Troubleshooting

For help, check out the #support channel on Discord. Our friendly Support Squad members are here to help!

You can also check our Astro Integration Documentation for more on integrations.

Contributing

This package is maintained by Astro's Core team. You're welcome to submit an issue or PR!

Options

This integration is powered by @sveltejs/vite-plugin-svelte. To customize the Svelte compiler, options can be provided to the integration. See the @sveltejs/vite-plugin-svelte docs for more details.

Default options

This integration passes the following default options to the Svelte compiler:

const defaultOptions = {
  emitCss: true,
  compilerOptions: { dev: isDev, hydratable: true },
  preprocess: vitePreprocess()
};

These emitCss, compilerOptions.dev, and compilerOptions.hydratable values are required to build properly for Astro and cannot be overridden.

Providing your own preprocess options will override the vitePreprocess() default. Make sure to enable the preprocessor flags needed for your project.

You can set options either by passing them to the svelte integration in astro.config.mjs or in svelte.config.js. Either of these would override the default preprocess setting:

// astro.config.mjs
import svelte from '@astrojs/svelte';

export default {
  integrations: [svelte({ preprocess: [] })],
};

// svelte.config.js
export default {
  preprocess: [],
};

Intellisense for TypeScript

If you're using a preprocessor like TypeScript or SCSS in your Svelte files, you can create a svelte.config.js file so that the Svelte IDE extension can correctly parse the Svelte files.

// svelte.config.js
import { vitePreprocess } from '@astrojs/svelte';

export default {
	preprocess: vitePreprocess(),
};

This config file will be automatically added for you when you run astro add svelte.