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@astrojs/ svelte

This Astro integration enables server-side rendering and client-side hydration for your Svelte components. It supports Svelte 3, 4, and 5 (experimental).

Astro includes an astro add command to automate the setup of official integrations. If you prefer, you can install integrations manually instead.

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

Terminal window
npx 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.

First, install the @astrojs/svelte package:

Terminal window
npm install @astrojs/svelte

Most package managers will install associated peer dependencies as well. If you see a “Cannot find package ‘svelte’” (or similar) warning when you start up Astro, you’ll need to install Svelte:

Terminal window
npm install svelte

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

astro.config.mjs
import { defineConfig } from 'astro/config';
import svelte from '@astrojs/svelte';
export default defineConfig({
// ...
integrations: [svelte()],
});

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

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.

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 { defineConfig } from 'astro/config';
import svelte from '@astrojs/svelte';
export default defineConfig({
integrations: [svelte({ preprocess: [] })],
});
svelte.config.js
export default {
preprocess: [],
};
Added in: @astrojs/svelte@2.0.0

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.

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