@visulima/packem

The main Packem package: a fast and modern bundler for Node.js and TypeScript. It ships the packem CLI, the configuration API, and the transformer integrations.

@visulima/packem is ESM-only ("type": "module" with no CommonJS exports). It requires Node.js ^22.14.0 || >= 24.10.0.

Installation

npm install @visulima/packem

CLI

The package exposes a single binary, packem:

{
  "bin": {
    "packem": "./dist/cli/index.js"
  }
}

packem build

Build the package using the resolved Packem configuration.

packem build [dir]

Selected options (run packem build --help for the full list):

• --bundler <rollup|rolldown> — Specify the bundler to use.
• --dir <dir> — The directory to build.
• --target <target> — Environments to support. The target in tsconfig.json is added automatically.
• --config <file> — Use a custom config file.
• --tsconfig <file> — Path to the tsconfig.json file.
• --minify — Minify the output.
• --sourcemap — Generate sourcemaps (experimental).
• --watch — Watch for changes.
• --jit — Stub the package for JIT compilation.
• --env.<KEY>=<value> — Compile-time environment variables (e.g. --env.NODE_ENV=production).
• --env-file <file> — Path to the .env file to load environment variables from.
• --env-prefix <prefix> — Prefix for environment variables to load from .env (default: PACKEM_).
• --metafile — Generate a meta file (experimental).
• --license <file> — Path to the license file.
• --analyze — Visualize and analyze the bundle.
• --cjsInterop — CJS interop mode (experimental).
• --production / --development — Run in production or development environment.
• --no-clean — Do not clean the dist directory before building.

packem init

Initialize a Packem configuration in your project.

packem init [dir]

Options:

• --dir <dir> — The directory to initialize.
• --transformer <name> — Choose a transformer.
• --css — Use CSS.
• --css-minifier <name> — Use a CSS minifier.
• --typescript — Use TypeScript.
• --runtime <nodejs|browser> — Specify the build runtime.

packem add

Add an optional Packem feature to your project.

packem add <feature>

Recognized features include typedoc, react, solid, preact, vue, svelte, and css.

Options:

• --dir <dir> — The directory to build.
• --config <file> — Use a custom config file.

packem migrate

Migrate from other bundlers (tsup, unbuild, bunchee, etc.) to Packem.

packem migrate [cwd]

Options:

• --cwd <dir> — The directory to migrate.
• --dry-run — Preview changes without applying them.

Programmatic API

The package root re-exports the packem runner alongside the core build types.

import { packem } from '@visulima/packem'

await packem('./', {
  mode: 'build',
  environment: 'production',
})

packem(rootDirectory, options?)

const packem = (rootDirectory: string, options?: PackemOptions) => Promise<void>

• rootDirectory (string) — The root directory of the project to bundle.
• options (PackemOptions) — Configuration options for the bundler.

PackemOptions

Extends BuildConfig with a few runner-level fields:

interface PackemOptions extends BuildConfig {
  /** The environment to build for. @default "production" */
  environment?: Environment
  /** Logger configuration options. */
  logger?: ConstructorOptions<string, string>
  /** The mode to run Packem in. @default "build" */
  mode?: Mode
}

Exported types

The package root also re-exports the following types:

import type {
  BuildEntry,
  BuildOptions,
  RollupBuildOptions,
} from '@visulima/packem'

import type {
  TransformerFn,
  TransformerName,
} from '@visulima/packem'

import type {
  BuildContext,
  BuildContextBuildAssetAndChunk,
  BuildContextBuildEntry,
  BuildHooks,
  Environment,
  Mode,
  Runtime,
} from '@visulima/packem'

Configuration — @visulima/packem/config

import { defineConfig } from '@visulima/packem/config'
import transformer from '@visulima/packem/transformer/esbuild'

export default defineConfig({
  transformer,
  entries: ['./src/index.ts'],
})

defineConfig(config)

Defines a build configuration. Accepts a static configuration object or a function that returns one.

const defineConfig = (
  config: BuildConfig | BuildConfigFunction,
) => BuildConfig | BuildConfigFunction

// Dynamic configuration
export default defineConfig((env, mode) => ({
  entries: ['./src/index.ts'],
  outDir: env === 'production' ? './dist' : './dev',
}))

definePreset(preset)

Defines a reusable build preset.

const definePreset = (preset: BuildPreset) => BuildPreset

export default definePreset({
  name: 'my-preset',
  defaults: {
    entries: ['./src/index.ts'],
  },
  hooks: {
    'build:before': (context) => {
      // Custom build preparation logic
    },
  },
})

Config types

The config subpath also re-exports these types:

import type {
  BuildConfig,
  BuildConfigFunction,
  BuildPreset,
  BuildHooks,
} from '@visulima/packem/config'

Framework presets

Ready-made presets are available as dedicated subpaths:

import react from '@visulima/packem/config/preset/react'
import preact from '@visulima/packem/config/preset/preact'
import solid from '@visulima/packem/config/preset/solid'
import svelte from '@visulima/packem/config/preset/svelte'
import vue from '@visulima/packem/config/preset/vue'

Transformers

Pick the transformer that compiles your TypeScript/JavaScript and pass it to transformer in your config.

esbuild

import transformer from '@visulima/packem/transformer/esbuild'

swc

import transformer from '@visulima/packem/transformer/swc'

OXC

import transformer from '@visulima/packem/transformer/oxc'

sucrase

import transformer from '@visulima/packem/transformer/sucrase'

Additional subpath exports

The package.json exports map also exposes:

• @visulima/packem/css/loader/{sourcemap,less,postcss,sass,stylus,lightningcss,tailwindcss} — CSS loaders.
• @visulima/packem/css/minifier/{cssnano,lightningcss} — CSS minifiers.
• @visulima/packem/builder/typedoc — TypeDoc documentation builder.
• @visulima/packem/files — Ambient declarations for asset imports (types only).
• @visulima/packem/package.json — The package manifest.

Related

• Packem Configuration
• Transformers Guide
• CLI Reference
• @visulima/packem-rollup