---
title: npm-dedupe
section: 1
description: Reduce duplication in the package tree
---

### Synopsis

```bash
npm dedupe
npm ddp

aliases: 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:

```bash
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.

### Configuration

<!-- AUTOGENERATED CONFIG DESCRIPTIONS START -->
<!-- automatically generated, do not edit manually -->
#### `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`.

#### `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 `npm install` runs to the default
registry and all registries configured for scopes. See the documentation for
[`npm audit`](/commands/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`](/commands/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 to selecting all of the
  nested workspaces)

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: false
* Type: Boolean

Enable running a command in the context of **all** the configured
workspaces.

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

<!-- AUTOGENERATED CONFIG DESCRIPTIONS END -->

### See Also

* [npm find-dupes](/commands/npm-find-dupes)
* [npm ls](/commands/npm-ls)
* [npm update](/commands/npm-update)
* [npm install](/commands/npm-install)
