bun install

Basic Usage

$ bun install react
$ bun install react@19.1.1 # specific version
$ bun install react@latest # specific tag

The bun CLI contains a Node.js-compatible package manager designed to be a dramatically faster replacement for npm, yarn, and pnpm. It's a standalone tool that works in existing Node.js projects; if your project has a package.json, you can use bun install.

To install all dependencies of a project:

$ bun install

bun install:

• Installs all dependencies, devDependencies, and optionalDependencies. Bun installs peerDependencies by default.
• Runs your project's {pre|post}install and {pre|post}prepare scripts at the appropriate time. For security reasons Bun does not execute lifecycle scripts of installed dependencies.
• Writes a bun.lock lockfile to the project root.

Logging

To modify logging verbosity:

$ bun install --verbose # debug logging
$ bun install --silent  # no logging

Lifecycle scripts

Unlike other npm clients, Bun does not execute arbitrary lifecycle scripts like postinstall for installed dependencies. Executing arbitrary scripts represents a potential security risk.

To tell Bun to allow lifecycle scripts for a particular package, add the package to trustedDependencies in your package.json.

{
  "name": "my-app",
  "version": "1.0.0",
  "trustedDependencies": ["my-trusted-package"] 
}

Then re-install the package. Bun reads this field and runs lifecycle scripts for my-trusted-package.

Lifecycle scripts run in parallel during installation. To adjust the maximum number of concurrent scripts, use the --concurrent-scripts flag. The default is two times the reported cpu count or GOMAXPROCS.

$ bun install --concurrent-scripts 5

Bun automatically optimizes postinstall scripts for popular packages (like esbuild and sharp) by determining which scripts need to run. To disable these optimizations:

$ BUN_FEATURE_FLAG_DISABLE_NATIVE_DEPENDENCY_LINKER=1 bun install
$ BUN_FEATURE_FLAG_DISABLE_IGNORE_SCRIPTS=1 bun install

Workspaces

Bun supports "workspaces" in package.json. See workspaces.

{
  "name": "my-app",
  "version": "1.0.0",
  "workspaces": ["packages/*"], 
  "dependencies": {
    "preact": "^10.5.13"
  }
}

Installing dependencies for specific packages

In a monorepo, you can install the dependencies for a subset of packages using the --filter flag.

# Install dependencies for all workspaces except `pkg-c`
$ bun install --filter '!pkg-c'

# Install dependencies for only `pkg-a` in `./packages/pkg-a`
$ bun install --filter './packages/pkg-a'

See filtering.

Overrides and resolutions

Bun supports npm's "overrides" and Yarn's "resolutions" in package.json. Both specify a version range for metadependencies, the dependencies of your dependencies. See overrides and resolutions.

{
  "name": "my-app",
  "dependencies": {
    "foo": "^2.0.0"
  },
  "overrides": { 
    "bar": "~4.4.0"
  } 
}

Global packages

To install a package globally, use the -g/--global flag. Use it to install command-line tools.

$ bun install --global cowsay # or `bun install -g cowsay`
$ cowsay "Bun!"

 ______
< Bun! >
 ------
        \   ^__^
         \  (oo)\_______
            (__)\       )\/\
                ||----w |
                ||     ||

Production mode

To install in production mode (without devDependencies):

$ bun install --production

For reproducible installs, use --frozen-lockfile. Bun installs the exact versions specified in the lockfile and does not update it. If your package.json disagrees with bun.lock, Bun exits with an error.

$ bun install --frozen-lockfile

See lockfile for more on bun.lock.

Omitting dependencies

To omit dev, peer, or optional dependencies, use the --omit flag.

# Exclude "devDependencies" from the installation. This will apply to the
# root package and workspaces if they exist. Transitive dependencies will
# not have "devDependencies".
$ bun install --omit dev

# Install only dependencies from "dependencies"
$ bun install --omit=dev --omit=peer --omit=optional

Dry run

To perform a dry run, without installing anything:

$ bun install --dry-run

Non-npm dependencies

Bun supports installing dependencies from Git, GitHub, and local or remotely-hosted tarballs. See bun add.

{
  "dependencies": {
    "dayjs": "git+https://github.com/iamkun/dayjs.git",
    "lodash": "git+ssh://github.com/lodash/lodash.git#4.17.21",
    "moment": "git@github.com:moment/moment.git",
    "zod": "github:colinhacks/zod",
    "react": "https://registry.npmjs.org/react/-/react-18.2.0.tgz",
    "bun-types": "npm:@types/bun"
  }
}

Installation strategies

Bun supports two package installation strategies that determine how dependencies are organized in node_modules:

Hoisted installs

The traditional npm/Yarn approach that flattens dependencies into a shared node_modules directory:

$ bun install --linker hoisted

Isolated installs

A pnpm-like approach that creates strict dependency isolation to prevent phantom dependencies, packages that can be imported without being declared in package.json:

$ bun install --linker isolated

Isolated installs create a central package store in node_modules/.bun/ with symlinks in the top-level node_modules. This ensures packages can only access their declared dependencies.

Default strategy

The default linker strategy depends on whether you're starting fresh or have an existing project:

• New workspaces/monorepos: isolated (prevents phantom dependencies)
• New single-package projects: hoisted (traditional npm behavior)
• Existing projects (made pre-v1.3.2): hoisted (preserves backward compatibility)

The default is controlled by a configVersion field in your lockfile. For a detailed explanation, see isolated installs.

Minimum release age

To protect against supply chain attacks where malicious packages are quickly published, you can configure a minimum age requirement for npm packages. Bun filters out package versions published more recently than the specified threshold (in seconds) during installation.

# Only install package versions published at least 3 days ago
$ bun add @types/bun --minimum-release-age 259200 # seconds

You can also configure this in bunfig.toml:

[install]
# Only install package versions published at least 3 days ago
minimumReleaseAge = 259200 # seconds

# Exclude trusted packages from the age gate
minimumReleaseAgeExcludes = ["@types/node", "typescript"]

When the minimum age filter is active:

• It only affects new package resolution; existing packages in bun.lock remain unchanged
• All dependencies (direct and transitive) are filtered to meet the age requirement when resolved
• When versions are blocked by the age gate, a stability check detects rapid bugfix patterns
  • If multiple versions were published close together just outside your age gate, Bun extends the filter to skip those potentially unstable versions and selects an older, more mature version
  • The check searches up to 7 days past the age gate; if releases are still rapid beyond that, Bun ignores the stability check
  • Exact version requests (like package@1.1.1) still respect the age gate but bypass the stability check
• Versions without a time field are treated as passing the age check (the npm registry should always provide timestamps)

For more advanced security scanning, including integration with services and custom filtering, see the Security Scanner API.

Configuration

Configuring bun install with bunfig.toml

On bun install, bun remove, and bun add, Bun looks for bunfig.toml in:

1. $XDG_CONFIG_HOME/.bunfig.toml or $HOME/.bunfig.toml
2. ./bunfig.toml

If both are found, the results are merged together.

Configuring with bunfig.toml is optional. These are the default values:

[install]

# whether to install optionalDependencies
optional = true

# whether to install devDependencies
dev = true

# whether to install peerDependencies
peer = true

# equivalent to `--production` flag
production = false

# equivalent to `--save-text-lockfile` flag
saveTextLockfile = true

# equivalent to `--frozen-lockfile` flag
frozenLockfile = false

# equivalent to `--dry-run` flag
dryRun = false

# equivalent to `--concurrent-scripts` flag
concurrentScripts = 16 # (cpu count or GOMAXPROCS) x2

# installation strategy: "hoisted" or "isolated"
# default depends on lockfile configVersion and workspaces:
# - configVersion = 1: "isolated" if using workspaces, otherwise "hoisted"
# - configVersion = 0: "hoisted"
linker = "hoisted"

# minimum age config
minimumReleaseAge = 259200 # seconds
minimumReleaseAgeExcludes = ["@types/node", "typescript"]

Configuring with environment variables

Environment variables take priority over bunfig.toml.

Bun uses the fastest installation method available on the target platform: clonefile on macOS and hardlink on Linux. You can change the installation method with the --backend flag. When unavailable or on error, clonefile and hardlink fall back to a platform-specific implementation of copying files.

Bun stores installed packages from npm in ~/.bun/install/cache/${name}@${version}. If the semver version has a build or a pre tag, Bun replaces it with a hash of that value. This reduces the chances of errors from long file paths, but complicates figuring out where a package was installed on disk.

When the node_modules folder exists, Bun decides whether to install a package by checking that the "name" and "version" in its package.json at the expected node_modules location match the expected name and version. It uses a custom JSON parser which stops parsing as soon as it finds "name" and "version".

When a bun.lock doesn’t exist or package.json has changed dependencies, Bun downloads and extracts tarballs eagerly while resolving.

When a bun.lock exists and package.json hasn’t changed, Bun downloads missing dependencies lazily. If the package with a matching name and version already exists in the expected location within node_modules, Bun won’t attempt to download the tarball.

CI/CD

Use the official oven-sh/setup-bun action to install bun in a GitHub Actions pipeline:

name: bun-types
jobs:
  build:
    name: build-app
    runs-on: ubuntu-latest
    steps:
      - name: Checkout repo
        uses: actions/checkout@v4
      - name: Install bun
        uses: oven-sh/setup-bun@v2
      - name: Install dependencies
        run: bun install
      - name: Build app
        run: bun run build

For CI/CD environments that want to enforce reproducible builds, use bun ci to fail the build if the package.json is out of sync with the lockfile:

$ bun ci

bun ci is equivalent to bun install --frozen-lockfile. It installs exact versions from bun.lock and fails if package.json doesn't match the lockfile. To use bun ci or bun install --frozen-lockfile, you must commit bun.lock to version control.

In your workflow, run bun ci instead of bun install:

name: bun-types
jobs:
  build:
    name: build-app
    runs-on: ubuntu-latest
    steps:
      - name: Checkout repo
        uses: actions/checkout@v4
      - name: Install bun
        uses: oven-sh/setup-bun@v2
      - name: Install dependencies
        run: bun ci
      - name: Build app
        run: bun run build

Platform-specific dependencies?

Bun stores normalized cpu and os values from npm in the lockfile, along with the resolved packages. It skips downloading, extracting, and installing packages disabled for the current target at runtime. This means the lockfile won't change between platforms/architectures even if the packages ultimately installed do change.

--cpu and --os flags

You can override the target platform for package selection:

$ bun install --cpu=x64 --os=linux

These flags install packages for the specified platform instead of the current system. Use them for cross-platform builds or when preparing deployments for different environments.

Accepted values for --cpu: arm, arm64, ia32, mips, mipsel, ppc, ppc64, s390, s390x, x32, x64

Accepted values for --os: aix, darwin, freebsd, linux, openbsd, sunos, win32, android

Peer dependencies?

Bun handles peer dependencies like Yarn: bun install installs them automatically. If the dependency is marked optional in peerDependenciesMeta, Bun uses an existing dependency if possible.

Lockfile

bun.lock is Bun’s lockfile format. See our blog post about the text lockfile.

Prior to Bun 1.2, the lockfile was binary and called bun.lockb. To upgrade an old lockfile to the new format, run bun install --save-text-lockfile --frozen-lockfile --lockfile-only, then delete bun.lockb.

Cache

To delete the cache:

$ bun pm cache rm
# or
$ rm -rf ~/.bun/install/cache

Platform-specific backends

For performance, bun install uses different system calls to install dependencies depending on the platform. You can force a specific backend with the --backend flag.

hardlink is the default backend on Linux. Benchmarking showed it to be the fastest on Linux.

$ rm -rf node_modules
$ bun install --backend hardlink

clonefile is the default backend on macOS. Benchmarking showed it to be the fastest on macOS. It is only available on macOS.

$ rm -rf node_modules
$ bun install --backend clonefile

clonefile_each_dir is similar to clonefile, except it clones each file individually per directory. It is only available on macOS and tends to perform slower than clonefile. Unlike clonefile, this does not recursively clone subdirectories in one system call.

$ rm -rf node_modules
$ bun install --backend clonefile_each_dir

copyfile is the fallback used when any of the above fail, and is the slowest. On macOS, it uses fcopyfile(); on Linux, it uses copy_file_range().

$ rm -rf node_modules
$ bun install --backend copyfile

symlink is typically only used for file: dependencies (and eventually link:) internally. To prevent infinite loops, it skips symlinking the node_modules folder.

If you install with --backend=symlink, Node.js won't resolve node_modules of dependencies unless each dependency has its own node_modules folder or you pass --preserve-symlinks to node or bun. See Node.js documentation on --preserve-symlinks.

$ rm -rf node_modules
$ bun install --backend symlink
$ bun --preserve-symlinks ./my-file.js
$ node --preserve-symlinks ./my-file.js # https://nodejs.org/api/cli.html#--preserve-symlinks

npm registry metadata

Bun uses a binary format for caching npm registry responses. This loads much faster than JSON and tends to be smaller on disk. These files live in ~/.bun/install/cache/*.npm. The filename pattern is ${hash(packageName)}.npm. It’s a hash so that extra directories don’t need to be created for scoped packages.

Bun's usage of Cache-Control ignores Age. This improves performance, but means Bun may be about 5 minutes behind the latest package version metadata from npm.

pnpm migration

Bun migrates projects from pnpm automatically. When a pnpm-lock.yaml file is detected and no bun.lock file exists, Bun converts the lockfile to bun.lock during installation. The original pnpm-lock.yaml file remains unmodified.

$ bun install

Migration only runs when bun.lock is absent. There is currently no opt-out flag for pnpm migration.

The migration process handles:

Lockfile Migration

• Converts pnpm-lock.yaml to bun.lock format
• Preserves package versions and resolution information
• Maintains dependency relationships and peer dependencies
• Handles patched dependencies with integrity hashes

Workspace Configuration

When a pnpm-workspace.yaml file exists, Bun migrates workspace settings to your root package.json:

packages:
  - "apps/*"
  - "packages/*"

catalog:
  react: ^18.0.0
  typescript: ^5.0.0

catalogs:
  build:
    webpack: ^5.0.0
    babel: ^7.0.0

Bun moves the workspace packages list and catalogs to the workspaces field in package.json:

{
  "workspaces": {
    "packages": ["apps/*", "packages/*"],
    "catalog": {
      "react": "^18.0.0",
      "typescript": "^5.0.0"
    },
    "catalogs": {
      "build": {
        "webpack": "^5.0.0",
        "babel": "^7.0.0"
      }
    }
  }
}

Catalog Dependencies

Dependencies using pnpm's catalog: protocol are preserved:

{
  "dependencies": {
    "react": "catalog:",
    "webpack": "catalog:build"
  }
}

Configuration Migration

Bun migrates the following pnpm configuration from both pnpm-lock.yaml and pnpm-workspace.yaml:

• Overrides: Moved from pnpm.overrides to root-level overrides in package.json
• Patched Dependencies: Moved from pnpm.patchedDependencies to root-level patchedDependencies in package.json
• Workspace Overrides: Applied from pnpm-workspace.yaml to root package.json

Requirements

• Requires pnpm lockfile version 7 or higher
• Workspace packages must have a name field in their package.json
• All catalog entries referenced by dependencies must exist in the catalogs definition

After migration, you can safely remove pnpm-lock.yaml and pnpm-workspace.yaml files.

CLI Usage

$ bun install <name>@<version>

General Configuration

Dependency Scope & Management

Dependency Type & Versioning

Lockfile Control

Network & Registry Settings

Installation Process Control

Caching Options

Output & Logging

Security & Integrity

Concurrency & Performance

Lifecycle Script Management

Help Information