output

Configuration options for the output bundle. These options control how Rolldown generates the final bundled files.

dir

Type: string
Optional: Yes ✅
Path: output.dir

The directory where output files will be written. Required when using multiple entry points.

Examples

export default {
  input: {
    main: 'src/index.js',
    admin: 'src/admin.js',
  },
  output: {
    dir: 'dist',
  },
};

file

Type: string
Optional: Yes ✅
Path: output.file

The file path for the output bundle. Used for single entry builds.

Examples

export default {
  input: 'src/index.js',
  output: {
    file: 'dist/bundle.js',
  },
};

In-depth

Use file for single-entry builds and dir for multi-entry builds.

exports

Type: 'auto' | 'named' | 'default' | 'none'
Default: 'auto'
Path: output.exports

Specifies what export mode to use for the bundle.

Examples

export default {
  output: {
    format: 'cjs',
    exports: 'named',
  },
};

In-depth

The available modes:

'auto': Automatically determines the export mode based on the entry module's exports (recommended)
'named': Exports are exposed as named exports
'default': The entry module's default export is used as the main export
'none': No exports (useful for side-effect-only bundles)

hashCharacters

Type: 'base64' | 'base36' | 'hex'
Default: 'base64'
Path: output.hashCharacters

The character set to use for content hashes in file names.

Examples

export default {
  output: {
    hashCharacters: 'hex',
    entryFileNames: '[name]-[hash].js',
  },
};

In-depth

The available character sets:

'base64': Uses base64 characters (shortest hashes)
'base36': Uses alphanumeric characters (0-9, a-z)
'hex': Uses hexadecimal characters (0-9, a-f)

format

Type: 'es' | 'cjs' | 'esm' | 'module' | 'commonjs' | 'iife' | 'umd'
Default: 'esm'
Path: output.format

Expected format of generated code.

Examples

export default {
  output: {
    format: 'esm',
  },
};

In-depth

The available formats:

'es', 'esm', 'module': ES module format (uses import and export)
'cjs', 'commonjs': CommonJS format (uses require() and module.exports)
'iife': Immediately Invoked Function Expression (requires name option)
'umd': Universal Module Definition (requires name option)

sourcemap

Type: boolean | 'inline' | 'hidden'
Default: false
Path: output.sourcemap

Controls source map generation and configuration. See output.sourcemap for detailed nested options.

Examples

export default {
  output: {
    sourcemap: true,
  },
};

Type: string | ((chunk: RenderedChunk) => string | Promise<string>)
Optional: Yes ✅
Path: output.banner

Code to prepend to the beginning of each output chunk.

Examples

export default {
  output: {
    banner: '/* My Library v1.0.0 | MIT License */',
  },
};

WARNING

When using output.banner or output.footer with minification enabled, the banner or footer content may be stripped out unless it is formatted as a legal comment. To ensure your banner or footer persists through minification, use one of these comment formats:

Comments starting with /*! (e.g., /*! My banner */)
Comments containing @license (e.g., /* @license My banner */)
Comments containing @preserve (e.g., /* @preserve My banner */)
Comments starting with //! (for single-line comments)

This behavior is controlled by the output.legalComments option, which defaults to 'inline' and preserves these special comment formats.

Type: string | ((chunk: RenderedChunk) => string | Promise<string>)
Optional: Yes ✅
Path: output.footer

Code to append to the end of each output chunk.

Examples

export default {
  output: {
    footer: '/* End of bundle */',
  },
};

WARNING

When using output.banner or output.footer with minification enabled, the footer content may be stripped out unless it is formatted as a legal comment. To ensure your footer persists through minification, use one of these comment formats:

Comments starting with /*! (e.g., /*! My banner */)
Comments containing @license (e.g., /* @license My banner */)
Comments containing @preserve (e.g., /* @preserve My banner */)
Comments starting with //! (for single-line comments)

This behavior is controlled by the output.legalComments option, which defaults to 'inline' and preserves these special comment formats.

intro

Type: string | ((chunk: RenderedChunk) => string | Promise<string>)
Optional: Yes ✅
Path: output.intro

Code to prepend inside the wrapper function (after banner, before actual code).

Examples

export default {
  output: {
    format: 'iife',
    intro: 'const ENVIRONMENT = "production";',
  },
};

outro

Type: string | ((chunk: RenderedChunk) => string | Promise<string>)
Optional: Yes ✅
Path: output.outro

Code to append inside the wrapper function (after actual code, before footer).

Examples

export default {
  output: {
    format: 'iife',
    outro: 'console.log("Bundle loaded");',
  },
};

extend

Type: boolean
Default: false
Path: output.extend

When true, extends the global variable defined by the name option rather than overwriting it. Only applies to iife and umd formats.

Examples

export default {
  output: {
    format: 'umd',
    name: 'MyLib',
    extend: true,
  },
};

esModule

Type: boolean | 'if-default-prop'
Default: 'if-default-prop'
Path: output.esModule

Controls whether to add a __esModule: true property when generating CJS output.

Examples

export default {
  output: {
    format: 'cjs',
    esModule: true,
  },
};

In-depth

The available options:

false: Never add __esModule property
true: Always add __esModule: true property
'if-default-prop': Only add if there's a default export

assetFileNames

Type: string | ((chunkInfo: PreRenderedAsset) => string)
Default: 'assets/[name]-[hash][extname]'
Path: output.assetFileNames

Pattern for naming asset files (non-JavaScript files).

Placeholders: [name], [hash], [extname]

Examples

export default {
  output: {
    assetFileNames: 'assets/[name].[hash][extname]',
  },
};

entryFileNames

Type: string | ((chunkInfo: PreRenderedChunk) => string)
Default: '[name].js'
Path: output.entryFileNames

Pattern for naming entry chunk files.

Placeholders: [name], [hash]

Examples

export default {
  output: {
    entryFileNames: '[name]-[hash].js',
  },
};

chunkFileNames

Type: string | ((chunkInfo: PreRenderedChunk) => string)
Default: '[name]-[hash].js'
Path: output.chunkFileNames

Pattern for naming non-entry chunk files (code-split chunks).

Placeholders: [name], [hash]

Examples

export default {
  output: {
    chunkFileNames: 'chunks/[name].[hash].js',
  },
};

cssEntryFileNames

Type: string | ((chunkInfo: PreRenderedChunk) => string)
Default: '[name].css'
Path: output.cssEntryFileNames

Pattern for naming CSS entry files.

Placeholders: [name], [hash]

Examples

export default {
  output: {
    cssEntryFileNames: 'styles/[name]-[hash].css',
  },
};

cssChunkFileNames

Type: string | ((chunkInfo: PreRenderedChunk) => string)
Default: '[name]-[hash].css'
Path: output.cssChunkFileNames

Pattern for naming CSS chunk files (non-entry CSS files).

Placeholders: [name], [hash]

Examples

export default {
  output: {
    cssChunkFileNames: 'styles/chunks/[name].[hash].css',
  },
};

sanitizeFileName

Type: boolean | ((name: string) => string)
Default: true
Path: output.sanitizeFileName

Controls sanitization of file names to ensure they're valid across different file systems.

Examples

export default {
  output: {
    sanitizeFileName: (name) => {
      return name.replace(/[^a-zA-Z0-9.-]/g, '_');
    },
  },
};

In-depth

The available options:

false: Disable sanitization
true: Enable default sanitization
Function: Custom sanitization logic

minify

Type: boolean | 'dce-only' | MinifyOptions
Default: false
Path: output.minify

Control code minification.

Examples

export default {
  output: {
    minify: true,
  },
};

In-depth

The available options:

false: Disable minification
true: Enable full minification
'dce-only': Only dead code elimination
Object: Fine-grained minification settings

name

Type: string
Optional: Yes ✅
Path: output.name

The global variable name for the bundle. Required when using iife or umd format.

Examples

export default {
  output: {
    format: 'iife',
    name: 'MyLibrary',
  },
};

globals

Type: Record<string, string> | ((name: string) => string)
Optional: Yes ✅
Path: output.globals

Maps external module IDs to global variable names for iife and umd formats.

Examples

export default {
  external: ['react', 'react-dom'],
  output: {
    format: 'iife',
    name: 'MyApp',
    globals: {
      'react': 'React',
      'react-dom': 'ReactDOM',
    },
  },
};

paths

Type: Record<string, string> | ((id: string) => string)
Optional: Yes ✅
Path: output.paths

Maps external module IDs to paths. Useful for loading dependencies from CDNs.

Examples

export default {
  external: ['d3', 'lodash'],
  output: {
    paths: {
      'd3': 'https://cdn.jsdelivr.net/npm/d3@7',
      'lodash': 'https://cdn.jsdelivr.net/npm/lodash@4',
    },
  },
};

generatedCode

Type: Partial<GeneratedCodeOptions>
Default: {}
Path: output.generatedCode

Configuration for the generated code output. See output.generatedCode for nested options.

externalLiveBindings

Type: boolean
Default: true
Path: output.externalLiveBindings

When true, generates code that supports live bindings for external imports.

Examples

export default {
  output: {
    externalLiveBindings: false,
  },
};

inlineDynamicImports

Type: boolean
Default: true for 'iife' and 'umd' formats, false otherwise
Path: output.inlineDynamicImports

When true, dynamic imports are inlined into the main bundle instead of being split into separate chunks.

Examples

export default {
  output: {
    inlineDynamicImports: true,
  },
};

manualChunks

Type: (moduleId: string, meta: { getModuleInfo: (moduleId: string) => ModuleInfo | null }) => string | NullValue
Optional: Yes ✅
Path: output.manualChunks

Deprecated

This option is deprecated. Please use output.advancedChunks instead.

Allows manual control over chunk creation.

advancedChunks

Type: object
Optional: Yes ✅
Path: output.advancedChunks

Advanced chunking configuration. See output.advancedChunks for nested options.

legalComments

Type: 'none' | 'inline'
Default: 'inline'
Path: output.legalComments

Control comments in the output.

Examples

export default {
  output: {
    legalComments: 'inline',
  },
};

In-depth

The available options:

'none': Remove all comments
'inline': Preserve comments containing @license, @preserve, or starting with //! or /*!

polyfillRequire

Type: boolean
Default: true
Path: output.polyfillRequire

When true, adds a polyfill for require() function in non-CommonJS formats.

Examples

export default {
  output: {
    format: 'esm',
    polyfillRequire: true,
  },
};

hoistTransitiveImports

Type: boolean
Default: true
Path: output.hoistTransitiveImports

When false, prevents hoisting transitive imports to entry chunks.

Examples

export default {
  output: {
    hoistTransitiveImports: false,
  },
};

preserveModules

Type: boolean
Default: false
Path: output.preserveModules

When true, preserves the module structure instead of creating a single bundle.

Examples

export default {
  input: 'src/index.js',
  output: {
    dir: 'dist',
    preserveModules: true,
  },
};

virtualDirname

Type: string
Optional: Yes ✅
Path: output.virtualDirname

Virtual directory name for resolving __dirname and __filename in the output.

Examples

export default {
  output: {
    virtualDirname: '/virtual',
  },
};

preserveModulesRoot

Type: string
Optional: Yes ✅
Path: output.preserveModulesRoot

Base path to use when preserving modules. All preserved modules will be placed relative to this path.

Examples

export default {
  output: {
    dir: 'dist',
    preserveModules: true,
    preserveModulesRoot: 'src',
  },
};

topLevelVar

Type: boolean
Default: false
Path: output.topLevelVar

When true, uses var declarations at the top level instead of function expressions.

Examples

export default {
  output: {
    topLevelVar: true,
  },
};

cleanDir

Type: boolean
Default: false
Path: output.cleanDir

Clean the output directory before emitting output. See output.cleanDir for detailed information.

minifyInternalExports

Type: boolean
Default: false
Path: output.minifyInternalExports

Whether to minify internal exports (exports not used by other chunks).

Examples

export default {
  output: {
    minifyInternalExports: true,
  },
};

keepNames

Type: boolean
Default: false
Path: output.keepNames

Preserve function and class names during bundling.

Examples

export default {
  output: {
    keepNames: true,
  },
};

In-depth

When enabled, the bundler will preserve the original names of functions and classes in the output, which is useful for:

Debugging and error stack traces
Code that relies on Function.prototype.name
Serialization that depends on constructor names

output ​

dir ​

Examples ​

file ​

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In-depth ​

exports ​

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hashCharacters ​

Examples ​

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format ​

Examples ​

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sourcemap ​

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banner ​

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footer ​

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intro ​

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outro ​

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extend ​

Examples ​

esModule ​

Examples ​

In-depth ​

assetFileNames ​

Examples ​

entryFileNames ​

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chunkFileNames ​

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cssEntryFileNames ​

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cssChunkFileNames ​

Examples ​

sanitizeFileName ​

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In-depth ​

minify ​

Examples ​

In-depth ​

name ​

Examples ​

globals ​

Examples ​

paths ​

Examples ​

generatedCode ​

externalLiveBindings ​

Examples ​

inlineDynamicImports ​

Examples ​

manualChunks ​

advancedChunks ​

legalComments ​

Examples ​

In-depth ​

polyfillRequire ​

Examples ​

hoistTransitiveImports ​

Examples ​

preserveModules ​

Examples ​

virtualDirname ​

Examples ​

preserveModulesRoot ​

Examples ​

topLevelVar ​

Examples ​

cleanDir ​

minifyInternalExports ​

Examples ​

keepNames ​

Examples ​

In-depth ​

output

dir

Examples

file

Examples

In-depth

exports

Examples

In-depth

hashCharacters

Examples

In-depth

format

Examples

In-depth

sourcemap

Examples

banner

Examples

footer

Examples

intro

Examples

outro

Examples

extend

Examples

esModule

Examples

In-depth

assetFileNames

Examples

entryFileNames

Examples

chunkFileNames

Examples

cssEntryFileNames

Examples

cssChunkFileNames

Examples

sanitizeFileName

Examples

In-depth

minify

Examples

In-depth

name

Examples

globals

Examples

paths

Examples

generatedCode

externalLiveBindings

Examples

inlineDynamicImports

Examples

manualChunks

advancedChunks

legalComments

Examples

In-depth

polyfillRequire

Examples

hoistTransitiveImports

Examples

preserveModules

Examples

virtualDirname

Examples

preserveModulesRoot

Examples

topLevelVar

Examples

cleanDir

minifyInternalExports

Examples

keepNames

Examples

In-depth