Bun bun install

bun install

Install packages with Bun's fast package manager

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 will work in pre-existing Node.js projects; if your project has a package.json, bun install can help you speed up your workflow.

To install all dependencies of a project:

bun install

Running bun install will:

• Install all dependencies, devDependencies, and optionalDependencies. Bun will install peerDependencies by default.
• Run 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.
• Write 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"] // [!code ++]
}

Then re-install the package. Bun will read this field and run lifecycle scripts for my-trusted-package.

Lifecycle scripts will 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, sharp, etc.) 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. For complete documentation refer to Package manager > Workspaces.

{
  "name": "my-app",
  "version": "1.0.0",
  "workspaces": ["packages/*"], // [!code ++]
  "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'

For more information on filtering with bun install, refer to Package Manager > Filtering

Overrides and resolutions

Bun supports npm's "overrides" and Yarn's "resolutions" in package.json. These are mechanisms for specifying a version range for metadependencies—the dependencies of your dependencies. Refer to Package manager > Overrides and resolutions for complete documentation.

{
  "name": "my-app",
  "dependencies": {
    "foo": "^2.0.0"
  },
  "overrides": { // [!code ++]
    "bar": "~4.4.0" // [!code ++]
  } // [!code ++]
}

Global packages

To install a package globally, use the -g/--global flag. Typically this is used for installing command-line tools.

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

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

Production mode

To install in production mode (i.e. without devDependencies or optionalDependencies):

bun install --production

For reproducible installs, use --frozen-lockfile. This will install the exact versions of each package specified in the lockfile. If your package.json disagrees with bun.lock, Bun will exit with an error. The lockfile will not be updated.

bun install --frozen-lockfile

For more information on Bun's lockfile bun.lock, refer to Package manager > Lockfile.

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 (i.e. don't actually install anything):

bun install --dry-run

Non-npm dependencies

Bun supports installing dependencies from Git, GitHub, and local or remotely-hosted tarballs. For complete documentation refer to Package manager > Git, GitHub, and tarball dependencies.

{
  "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:

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 Package manager > 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. Package versions published more recently than the specified threshold (in seconds) will be filtered out 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:

• 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 being 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, it extends the filter to skip those potentially unstable versions and selects an older, more mature version
  • Searches up to 7 days after the age gate, however if still finding rapid releases it ignores 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 (npm registry should always provide timestamps)

For more advanced security scanning, including integration with services & custom filtering, see Package manager > Security Scanner API.

Configuration

Configuring bun install with bunfig.toml

bunfig.toml is searched for in the following paths on bun install, bun remove, and bun add:

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. Bun tries to be zero configuration in general, but that's not always possible. The default behavior of bun install can be configured in bunfig.toml. The default values are shown below.

[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 = false

# 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 have a higher priority than bunfig.toml.

Bun always tries to use the fastest available installation method for the target platform. On macOS, that’s clonefile and on Linux, that’s hardlink. You can change which installation method is used with the --backend flag. When unavailable or on error, clonefile and hardlink fallsback to a platform-specific implementation of copying files.

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

When the node_modules folder exists, before installing, Bun checks if the "name" and "version" in package/package.json in the expected node_modules folder matches the expected name and version. This is how it determines whether it should install. 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, tarballs are downloaded & extracted 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 & 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

This 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.

And instead of running bun install, run bun ci.

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

This installs packages for the specified platform instead of the current system. Useful for cross-platform builds or when preparing deployments for different environments.

Accepted values for --cpu: arm64, x64, ia32, ppc64, s390x

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

Peer dependencies?

Peer dependencies are handled similarly to yarn. bun install will automatically install peer dependencies. If the dependency is marked optional in peerDependenciesMeta, an existing dependency will be chosen if possible.

Lockfile

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

Prior to Bun 1.2, the lockfile was binary and called bun.lockb. Old lockfiles can be upgraded to the new format by running bun install --save-text-lockfile --frozen-lockfile --lockfile-only, and then deleting bun.lockb.

Cache

To delete the cache:

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

Platform-specific backends

bun install uses different system calls to install dependencies depending on the platform. This is a performance optimization. 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() and 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. You will see these files 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 out of date to receive the latest package version metadata from npm.

pnpm migration

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

bun install

Note: 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

The workspace packages list and catalogs are moved 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

The following pnpm configuration is migrated 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