@vrowzer/rolldown

Pre-bundled @rolldown/browser for easy browser usage. All dependencies (@napi-rs/wasm-runtime, memfs, etc.) are pre-resolved, and the internal memfs is replaced with @vrowzer/fs for filesystem instance sharing.

🤔 Why?

@rolldown/browser cannot be used with a simple import in the browser because:

• rolldown-binding.wasi-browser.js imports @napi-rs/wasm-runtime via bare specifiers (not resolvable in browsers)
• Worker scripts also use bare specifier imports
• WASM binary URL is resolved via import.meta.url relative paths
• SharedArrayBuffer requires Cross-Origin-Opener-Policy and Cross-Origin-Embedder-Policy headers

This package pre-bundles everything so that bare specifiers are resolved and all files are co-located.

🚀 Usage

Two build types are provided:

Shared build: @vrowzer/fs external (for Web Worker / shared filesystem)

@vrowzer/fs is not bundled. The consumer provides @vrowzer/fs, allowing rolldown and other code to share the same memfs Volume instance.

import { rolldown } from '@vrowzer/rolldown'
import { memfs } from '@vrowzer/rolldown/experimental'

memfs.volume.fromJSON({
  '/src/index.js': 'import { add } from "./math.js"\nconsole.log(add(1, 2))',
  '/src/math.js': 'export function add(a, b) { return a + b }'
})

const bundle = await rolldown({ input: '/src/index.js', cwd: '/' })
const { output } = await bundle.generate({ format: 'esm' })
console.log(output[0].code)

Standalone build: Fully self-contained (for browser)

@vrowzer/fs is bundled. No additional dependencies needed.

import { rolldown } from '@vrowzer/rolldown/browser'
import { memfs } from '@vrowzer/rolldown/browser/experimental'

memfs.volume.fromJSON({
  '/src/index.js': 'export const x = 1'
})

const bundle = await rolldown({ input: '/src/index.js', cwd: '/' })
const { output } = await bundle.generate({ format: 'esm' })

Exports

@vrowzer/rolldown / @vrowzer/rolldown/browser

Re-exports from @rolldown/browser:

• rolldown - Main bundler function
• VERSION - Rolldown version string

@vrowzer/rolldown/experimental / @vrowzer/rolldown/browser/experimental

Re-exports from @rolldown/browser/experimental:

• memfs - In-memory filesystem ({ fs, volume }) backed by @vrowzer/fs
• parseSync / parse - OXC-based JavaScript/TypeScript parser
• transform / transformSync - Code transformation

@vrowzer/rolldown/utils / @vrowzer/rolldown/browser/utils

Re-exports from @rolldown/browser/experimental, compatible with rolldown/utils:

• transform / transformSync - Code transformation (TypeScript strip, define replacement)
• parse / parseSync - OXC-based JavaScript/TypeScript parser
• minify / minifySync - OXC-based code minification
• TsconfigCache - TypeScript config resolution cache
• TransformOptions / TransformResult / ParseResult / ParserOptions / MinifyOptions / MinifyResult - TypeScript types

HTTP Headers

SharedArrayBuffer is required by the rolldown WASM runtime. The following HTTP headers must be set on the server:

Cross-Origin-Opener-Policy: same-origin
Cross-Origin-Embedder-Policy: require-corp

Build

The package is built using rolldown itself:

pnpm build

This produces:

dist/
├── index.js                          # Shared build: main entry (@vrowzer/fs external)
├── experimental.js                   # Shared build: experimental (@vrowzer/fs external)
├── utils.js                          # Shared build: utils (transformSync)
├── chunks/                           # Shared build: shared chunks
├── worker.js                         # Shared: bundled WASI worker script
├── rolldown-binding.wasm32-wasi.wasm # Shared: WASM binary (~11MB)
└── browser/
    ├── index.js                      # Standalone build: main entry (@vrowzer/fs bundled)
    ├── experimental.js               # Standalone build: experimental (@vrowzer/fs bundled)
    ├── utils.js                      # Standalone build: utils (transformSync)
    └── chunks/                       # Standalone build: shared chunks

Both builds share the same worker.js and WASM binary. Within each variant, index.js and experimental.js share the same binding instance via code splitting, ensuring that files written via memfs are visible to rolldown().

Key build transformations

• @napi-rs/wasm-runtime/fs internal memfs is replaced with @vrowzer/fs
• process.cwd() is replaced with "/"
• fs-proxy IPC buffer is expanded from ~10KB to ~10MB
• Worker and WASM URLs are adjusted for the chunks/ subdirectory layout

🤝 Sponsors

©️ License

MIT