npm command-line interface

# npm-dedupe

Reduce duplication in the package tree

## Table of contents

- Synopsis
- Description
- Configuration

- `global-style`
- `legacy-bundling`
- `strict-peer-deps`
- `package-lock`
- `save`
- `omit`
- `ignore-scripts`
- `audit`
- `bin-links`
- `fund`
- `dry-run`
- `workspace`
- `workspaces`
- `include-workspace-root`

- See Also

### Synopsis

    npm dedupe

    alias: ddp

### Description

Searches the local package tree and attempts to simplify the overall structure by moving dependencies further up the tree, where they can be more effectively shared by multiple dependent packages.

For example, consider this dependency graph:

    a
    +-- b <-- depends on c@1.0.x
    |   `-- c@1.0.3
    `-- d <-- depends on c@~1.0.9
        `-- c@1.0.10

In this case, `npm dedupe` will transform the tree to:

    a
    +-- b
    +-- d
    `-- c@1.0.10

Because of the hierarchical nature of node's module lookup, b and d will both get their dependency met by the single c package at the root level of the tree.

In some cases, you may have a dependency graph like this:

    a
    +-- b <-- depends on c@1.0.x
    +-- c@1.0.3
    `-- d <-- depends on c@1.x
        `-- c@1.9.9

During the installation process, the `c@1.0.3` dependency for `b` was placed in the root of the tree. Though `d`'s dependency on `c@1.x` could have been satisfied by `c@1.0.3`, the newer `c@1.9.0` dependency was used, because npm favors updates by default, even when doing so causes duplication.

Running `npm dedupe` will cause npm to note the duplication and re-evaluate, deleting the nested `c` module, because the one in the root is sufficient.

To prefer deduplication over novelty during the installation process, run `npm install --prefer-dedupe` or `npm config set prefer-dedupe true`.

Arguments are ignored. Dedupe always acts on the entire tree.

Note that this operation transforms the dependency tree, but will never result in new modules being installed.

Using `npm find-dupes` will run the command in `--dry-run` mode.

Note that by default `npm dedupe` will not update the semver values of direct dependencies in your project `package.json`, if you want to also update values in `package.json` you can run: `npm dedupe --save` (or add the `save=true` option to a configuration file to make that the default behavior).

### Configuration

#### `global-style`

- Default: false
- Type: Boolean

Causes npm to install the package into your local `node_modules` folder with the same layout it uses with the global `node_modules` folder. Only your direct dependencies will show in `node_modules` and everything they depend on will be flattened in their `node_modules` folders. This obviously will eliminate some deduping. If used with `legacy-bundling`, `legacy-bundling` will be preferred.

#### `legacy-bundling`

- Default: false
- Type: Boolean

Causes npm to install the package such that versions of npm prior to 1.4, such as the one included with node 0.8, can install the package. This eliminates all automatic deduping. If used with `global-style` this option will be preferred.

#### `strict-peer-deps`

- Default: false
- Type: Boolean

If set to `true`, and `--legacy-peer-deps` is not set, then any conflicting `peerDependencies` will be treated as an install failure, even if npm could reasonably guess the appropriate resolution based on non-peer dependency relationships.

By default, conflicting `peerDependencies` deep in the dependency graph will be resolved using the nearest non-peer dependency specification, even if doing so will result in some packages receiving a peer dependency outside the range set in their package's `peerDependencies` object.

When such and override is performed, a warning is printed, explaining the conflict and the packages involved. If `--strict-peer-deps` is set, then this warning is treated as a failure.

#### `package-lock`

- Default: true
- Type: Boolean

If set to false, then ignore `package-lock.json` files when installing. This will also prevent writing `package-lock.json` if `save` is true.

When package package-locks are disabled, automatic pruning of extraneous modules will also be disabled. To remove extraneous modules with package-locks disabled use `npm prune`.

This configuration does not affect `npm ci`.

#### `save`

- Default: `true` unless when using `npm update` or `npm dedupe` where it defaults to `false`
- Type: Boolean

Save installed packages to a `package.json` file as dependencies.

When used with the `npm rm` command, removes the dependency from `package.json`.

Will also prevent writing to `package-lock.json` if set to `false`.

#### `omit`

- Default: 'dev' if the `NODE_ENV` environment variable is set to 'production', otherwise empty.
- Type: "dev", "optional", or "peer" (can be set multiple times)

Dependency types to omit from the installation tree on disk.

Note that these dependencies are still resolved and added to the `package-lock.json` or `npm-shrinkwrap.json` file. They are just not physically installed on disk.

If a package type appears in both the `--include` and `--omit` lists, then it will be included.

If the resulting omit list includes `'dev'`, then the `NODE_ENV` environment variable will be set to `'production'` for all lifecycle scripts.

#### `ignore-scripts`

- Default: false
- Type: Boolean

If true, npm does not run scripts specified in package.json files.

Note that commands explicitly intended to run a particular script, such as `npm start`, `npm stop`, `npm restart`, `npm test`, and `npm run-script` will still run their intended script if `ignore-scripts` is set, but they will not run any pre- or post-scripts.

#### `audit`

- Default: true
- Type: Boolean

When "true" submit audit reports alongside the current npm command to the default registry and all registries configured for scopes. See the documentation for `npm audit` for details on what is submitted.

#### `bin-links`

- Default: true
- Type: Boolean

Tells npm to create symlinks (or `.cmd` shims on Windows) for package executables.

Set to false to have it not do this. This can be used to work around the fact that some file systems don't support symlinks, even on ostensibly Unix systems.

#### `fund`

- Default: true
- Type: Boolean

When "true" displays the message at the end of each `npm install` acknowledging the number of dependencies looking for funding. See `npm fund` for details.

#### `dry-run`

- Default: false
- Type: Boolean

Indicates that you don't want npm to make any changes and that it should only report what it would have done. This can be passed into any of the commands that modify your local installation, eg, `install`, `update`, `dedupe`, `uninstall`, as well as `pack` and `publish`.

Note: This is NOT honored by other network related commands, eg `dist-tags`, `owner`, etc.

#### `workspace`

- Default:
- Type: String (can be set multiple times)

Enable running a command in the context of the configured workspaces of the current project while filtering by running only the workspaces defined by this configuration option.

Valid values for the `workspace` config are either:

- Workspace names
- Path to a workspace directory
- Path to a parent workspace directory (will result in selecting all workspaces within that folder)

When set for the `npm init` command, this may be set to the folder of a workspace which does not yet exist, to create the folder and set it up as a brand new workspace within the project.

This value is not exported to the environment for child processes.

#### `workspaces`

- Default: null
- Type: null or Boolean

Set to true to run the command in the context of all configured workspaces.

Explicitly setting this to false will cause commands like `install` to ignore workspaces altogether. When not set explicitly:

- Commands that operate on the `node_modules` tree (install, update, etc.) will link workspaces into the `node_modules` folder. - Commands that do other things (test, exec, publish, etc.) will operate on the root project, unless one or more workspaces are specified in the `workspace` config.

This value is not exported to the environment for child processes.

#### `include-workspace-root`

- Default: false
- Type: Boolean

Include the workspace root when workspaces are enabled for a command.

When false, specifying individual workspaces via the `workspace` config, or all workspaces via the `workspaces` flag, will cause npm to operate only on the specified workspaces, and not on the root project.

### See Also

- npm find-dupes
- npm ls
- npm update
- npm install