Svelte Support

Build Svelte component libraries with tsdown using rollup-plugin-svelte.

Quick Start

npx create-tsdown@latest -t svelte

Configuration

import svelte from 'rollup-plugin-svelte'
import { sveltePreprocess } from 'svelte-preprocess'
import { defineConfig } from 'tsdown'

export default defineConfig({
  entry: ['./src/index.ts'],
  platform: 'neutral',
  plugins: [svelte({ preprocess: sveltePreprocess() })],
})

Dependencies

npm install -D rollup-plugin-svelte svelte svelte-preprocess

Distribution Strategy

Recommended: Ship .svelte source files instead of precompiled JS. Let consumers' tooling (Vite + @sveltejs/vite-plugin-svelte) compile in their apps.

Reasons:

Avoids version compatibility issues with svelte/internal
Better SSR/hydration consistency
Consumers get better HMR, diagnostics, and tree-shaking
Fewer republish cycles on Svelte upgrades

Exceptions where shipping JS makes sense:

Web Components via customElement mode
CDN direct-load without a build step

Key Points

Mark svelte/svelte/* as external; declare svelte in peerDependencies
Use svelte2tsx to emit .d.ts for Svelte components
Keep .svelte in source form for distribution

Plugins - Plugin configuration
Dependencies - External dependencies

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