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section: configuring-npm title: folders description: Folder Structures Used by npm

folders(5)

Folder Structures Used by npm

Description

npm puts various things on your computer. That's its job.

This document will tell you what it puts where.

tl;dr

  • Local install (default): puts stuff in ./node_modules of the current package root.
  • Global install (with -g): puts stuff in /usr/local or wherever node is installed.
  • Install it locally if you're going to require() it.
  • Install it globally if you're going to run it on the command line.
  • If you need both, then install it in both places, or use npm link.

prefix Configuration

The prefix config defaults to the location where node is installed. On most systems, this is /usr/local. On Windows, it's %AppData%\npm. On Unix systems, it's one level up, since node is typically installed at {prefix}/bin/node rather than {prefix}/node.exe.

When the global flag is set, npm installs things into this prefix. When it is not set, it uses the root of the current package, or the current working directory if not in a package already.

Node Modules

Packages are dropped into the node_modules folder under the prefix. When installing locally, this means that you can require("packagename") to load its main module, or require("packagename/lib/path/to/sub/module") to load other modules.

Global installs on Unix systems go to {prefix}/lib/node_modules. Global installs on Windows go to {prefix}/node_modules (that is, no lib folder.)

Scoped packages are installed the same way, except they are grouped together in a sub-folder of the relevant node_modules folder with the name of that scope prefix by the @ symbol, e.g. npm install @myorg/package would place the package in {prefix}/node_modules/@myorg/package. See scope for more details.

If you wish to require() a package, then install it locally.

Executables

When in global mode, executables are linked into {prefix}/bin on Unix, or directly into {prefix} on Windows.

When in local mode, executables are linked into ./node_modules/.bin so that they can be made available to scripts run through npm. (For example, so that a test runner will be in the path when you run npm test.)

Man Pages

When in global mode, man pages are linked into {prefix}/share/man.

When in local mode, man pages are not installed.

Man pages are not installed on Windows systems.

Cache

See npm cache. Cache files are stored in ~/.npm on Posix, or %AppData%/npm-cache on Windows.

This is controlled by the cache configuration param.

Temp Files

Temporary files are stored by default in the folder specified by the tmp config, which defaults to the TMPDIR, TMP, or TEMP environment variables, or /tmp on Unix and c:\windows\temp on Windows.

Temp files are given a unique folder under this root for each run of the program, and are deleted upon successful exit.

More Information

When installing locally, npm first tries to find an appropriate prefix folder. This is so that npm install foo@1.2.3 will install to the sensible root of your package, even if you happen to have cded into some other folder.

Starting at the $PWD, npm will walk up the folder tree checking for a folder that contains either a package.json file, or a node_modules folder. If such a thing is found, then that is treated as the effective "current directory" for the purpose of running npm commands. (This behavior is inspired by and similar to git's .git-folder seeking logic when running git commands in a working dir.)

If no package root is found, then the current folder is used.

When you run npm install foo@1.2.3, then the package is loaded into the cache, and then unpacked into ./node_modules/foo. Then, any of foo's dependencies are similarly unpacked into ./node_modules/foo/node_modules/....

Any bin files are symlinked to ./node_modules/.bin/, so that they may be found by npm scripts when necessary.

Global Installation

If the global configuration is set to true, then npm will install packages "globally".

For global installation, packages are installed roughly the same way, but using the folders described above.

Cycles, Conflicts, and Folder Parsimony

Cycles are handled using the property of node's module system that it walks up the directories looking for node_modules folders. So, at every stage, if a package is already installed in an ancestor node_modules folder, then it is not installed at the current location.

Consider the case above, where foo -> bar -> baz. Imagine if, in addition to that, baz depended on bar, so you'd have: foo -> bar -> baz -> bar -> baz .... However, since the folder structure is: foo/node_modules/bar/node_modules/baz, there's no need to put another copy of bar into .../baz/node_modules, since when it calls require("bar"), it will get the copy that is installed in foo/node_modules/bar.

This shortcut is only used if the exact same version would be installed in multiple nested node_modules folders. It is still possible to have a/node_modules/b/node_modules/a if the two "a" packages are different versions. However, without repeating the exact same package multiple times, an infinite regress will always be prevented.

Another optimization can be made by installing dependencies at the highest level possible, below the localized "target" folder.

Example

Consider this dependency graph:

foo
+-- blerg@1.2.5
+-- bar@1.2.3
|   +-- blerg@1.x (latest=1.3.7)
|   +-- baz@2.x
|   |   `-- quux@3.x
|   |       `-- bar@1.2.3 (cycle)
|   `-- asdf@*
`-- baz@1.2.3
    `-- quux@3.x
        `-- bar

In this case, we might expect a folder structure like this:

foo
+-- node_modules
    +-- blerg (1.2.5) <---[A]
    +-- bar (1.2.3) <---[B]
    |   `-- node_modules
    |       +-- baz (2.0.2) <---[C]
    |       |   `-- node_modules
    |       |       `-- quux (3.2.0)
    |       `-- asdf (2.3.4)
    `-- baz (1.2.3) <---[D]
        `-- node_modules
            `-- quux (3.2.0) <---[E]

Since foo depends directly on bar@1.2.3 and baz@1.2.3, those are installed in foo's node_modules folder.

Even though the latest copy of blerg is 1.3.7, foo has a specific dependency on version 1.2.5. So, that gets installed at [A]. Since the parent installation of blerg satisfies bar's dependency on blerg@1.x, it does not install another copy under [B].

Bar [B] also has dependencies on baz and asdf, so those are installed in bar's node_modules folder. Because it depends on baz@2.x, it cannot re-use the baz@1.2.3 installed in the parent node_modules folder [D], and must install its own copy [C].

Underneath bar, the baz -> quux -> bar dependency creates a cycle. However, because bar is already in quux's ancestry [B], it does not unpack another copy of bar into that folder.

Underneath foo -> baz [D], quux's [E] folder tree is empty, because its dependency on bar is satisfied by the parent folder copy installed at [B].

For a graphical breakdown of what is installed where, use npm ls.

Publishing

Upon publishing, npm will look in the node_modules folder. If any of the items there are not in the bundledDependencies array, then they will not be included in the package tarball.

This allows a package maintainer to install all of their dependencies (and dev dependencies) locally, but only re-publish those items that cannot be found elsewhere. See package.json for more information.

See also

section: configuring-npm title: install description: Download and install node and npm

install(5)

Download and Install npm

Description

To publish and install packages to and from the public npm registry, you must install Node.js and the npm command line interface using either a Node version manager or a Node installer. We strongly recommend using a Node version manager to install Node.js and npm. We do not recommend using a Node installer, since the Node installation process installs npm in a directory with local permissions and can cause permissions errors when you run npm packages globally.

Overview

Checking your version of npm and Node.js

To see if you already have Node.js and npm installed and check the installed version, run the following commands:

node -v
npm -v

Using a Node version manager to install Node.js and npm

Node version managers allow you to install and switch between multiple versions of Node.js and npm on your system so you can test your applications on multiple versions of npm to ensure they work for users on different versions.

OSX or Linux Node version managers

Windows Node version managers

Using a Node installer to install Node.js and npm

If you are unable to use a Node version manager, you can use a Node installer to install both Node.js and npm on your system.

OS X or Windows Node installers

If you're using OS X or Windows, use one of the installers from the Node.js download page. Be sure to install the version labeled LTS. Other versions have not yet been tested with npm.

Linux or other operating systems Node installers

If you're using Linux or another operating system, use one of the following installers:

Or see this page to install npm for Linux in the way many Linux developers prefer.

Less-common operating systems

For more information on installing Node.js on a variety of operating systems, see this page.

section: configuring-npm title: npmrc description: The npm config files

npmrc(5)

The npm config files

Description

npm gets its config settings from the command line, environment variables, and npmrc files.

The npm config command can be used to update and edit the contents of the user and global npmrc files.

For a list of available configuration options, see config.

Files

The four relevant files are:

  • per-project config file (/path/to/my/project/.npmrc)
  • per-user config file (~/.npmrc)
  • global config file ($PREFIX/etc/npmrc)
  • npm builtin config file (/path/to/npm/npmrc)

All npm config files are an ini-formatted list of key = value parameters. Environment variables can be replaced using ${VARIABLE_NAME}. For example:

prefix = ${HOME}/.npm-packages

Each of these files is loaded, and config options are resolved in priority order. For example, a setting in the userconfig file would override the setting in the globalconfig file.

Array values are specified by adding "[]" after the key name. For example:

key[] = "first value"
key[] = "second value"

Comments

Lines in .npmrc files are interpreted as comments when they begin with a ; or # character. .npmrc files are parsed by npm/ini, which specifies this comment syntax.

For example:

# last modified: 01 Jan 2016
; Set a new registry for a scoped package
@myscope:registry=https://mycustomregistry.example.org

Per-project config file

When working locally in a project, a .npmrc file in the root of the project (ie, a sibling of node_modules and package.json) will set config values specific to this project.

Note that this only applies to the root of the project that you're running npm in. It has no effect when your module is published. For example, you can't publish a module that forces itself to install globally, or in a different location.

Additionally, this file is not read in global mode, such as when running npm install -g.

Per-user config file

$HOME/.npmrc (or the userconfig param, if set in the environment or on the command line)

Global config file

$PREFIX/etc/npmrc (or the globalconfig param, if set above): This file is an ini-file formatted list of key = value parameters. Environment variables can be replaced as above.

Built-in config file

path/to/npm/itself/npmrc

This is an unchangeable "builtin" configuration file that npm keeps consistent across updates. Set fields in here using the ./configure script that comes with npm. This is primarily for distribution maintainers to override default configs in a standard and consistent manner.

See also

section: configuring-npm title: package.json description: Specifics of npm's package.json handling

package.json(5)

Specifics of npm's package.json handling

Description

This document is all you need to know about what's required in your package.json file. It must be actual JSON, not just a JavaScript object literal.

A lot of the behavior described in this document is affected by the config settings described in config.

name

If you plan to publish your package, the most important things in your package.json are the name and version fields as they will be required. The name and version together form an identifier that is assumed to be completely unique. Changes to the package should come along with changes to the version. If you don't plan to publish your package, the name and version fields are optional.

The name is what your thing is called.

Some rules:

  • The name must be less than or equal to 214 characters. This includes the scope for scoped packages.
  • The names of scoped packages can begin with a dot or an underscore. This is not permitted without a scope.
  • New packages must not have uppercase letters in the name.
  • The name ends up being part of a URL, an argument on the command line, and a folder name. Therefore, the name can't contain any non-URL-safe characters.

Some tips:

  • Don't use the same name as a core Node module.
  • Don't put "js" or "node" in the name. It's assumed that it's js, since you're writing a package.json file, and you can specify the engine using the "engines" field. (See below.)
  • The name will probably be passed as an argument to require(), so it should be something short, but also reasonably descriptive.
  • You may want to check the npm registry to see if there's something by that name already, before you get too attached to it. https://www.npmjs.com/

A name can be optionally prefixed by a scope, e.g. @myorg/mypackage. See scope for more detail.

version

If you plan to publish your package, the most important things in your package.json are the name and version fields as they will be required. The name and version together form an identifier that is assumed to be completely unique. Changes to the package should come along with changes to the version. If you don't plan to publish your package, the name and version fields are optional.

Version must be parseable by node-semver, which is bundled with npm as a dependency. (npm install semver to use it yourself.)

More on version numbers and ranges at semver.

description

Put a description in it. It's a string. This helps people discover your package, as it's listed in npm search.

keywords

Put keywords in it. It's an array of strings. This helps people discover your package as it's listed in npm search.

homepage

The url to the project homepage.

Example:

"homepage": "https://github.com/owner/project#readme"

bugs

The url to your project's issue tracker and / or the email address to which issues should be reported. These are helpful for people who encounter issues with your package.

It should look like this:

{
  "url": "https://github.com/owner/project/issues",
  "email": "project@hostname.com"
}

You can specify either one or both values. If you want to provide only a url, you can specify the value for "bugs" as a simple string instead of an object.

If a url is provided, it will be used by the npm bugs command.

license

You should specify a license for your package so that people know how they are permitted to use it, and any restrictions you're placing on it.

If you're using a common license such as BSD-2-Clause or MIT, add a current SPDX license identifier for the license you're using, like this:

{ "license": "BSD-3-Clause" }

You can check the full list of SPDX license IDs. Ideally you should pick one that is OSI approved.

If your package is licensed under multiple common licenses, use an SPDX license expression syntax version 2.0 string, like this:

{ "license": "(ISC OR GPL-3.0)" }

If you are using a license that hasn't been assigned an SPDX identifier, or if you are using a custom license, use a string value like this one:

{ "license": "SEE LICENSE IN <filename>" }

Then include a file named <filename> at the top level of the package.

Some old packages used license objects or a "licenses" property containing an array of license objects:

// Not valid metadata
{ "license" :
  { "type" : "ISC"
  , "url" : "https://opensource.org/licenses/ISC"
  }
}

// Not valid metadata
{ "licenses" :
  [
    { "type": "MIT"
    , "url": "https://www.opensource.org/licenses/mit-license.php"
    }
  , { "type": "Apache-2.0"
    , "url": "https://opensource.org/licenses/apache2.0.php"
    }
  ]
}

Those styles are now deprecated. Instead, use SPDX expressions, like this:

{ "license": "ISC" }

{ "license": "(MIT OR Apache-2.0)" }

Finally, if you do not wish to grant others the right to use a private or unpublished package under any terms:

{ "license": "UNLICENSED" }

Consider also setting "private": true to prevent accidental publication.

people fields: author, contributors

The "author" is one person. "contributors" is an array of people. A "person" is an object with a "name" field and optionally "url" and "email", like this:

{
  "name": "Barney Rubble",
  "email": "b@rubble.com",
  "url": "http://barnyrubble.tumblr.com/"
}

Or you can shorten that all into a single string, and npm will parse it for you:

"Barney Rubble <b@rubble.com> (http://barnyrubble.tumblr.com/)"

Both email and url are optional either way.

npm also sets a top-level "maintainers" field with your npm user info.

funding

You can specify an object containing an URL that provides up-to-date information about ways to help fund development of your package, or a string URL, or an array of these:

"funding": {
  "type" : "individual",
  "url" : "http://example.com/donate"
}

"funding": {
  "type" : "patreon",
  "url" : "https://www.patreon.com/my-account"
}

"funding": "http://example.com/donate"

"funding": [
  {
    "type" : "individual",
    "url" : "http://example.com/donate"
  },
  "http://example.com/donateAlso",
  {
    "type" : "patreon",
    "url" : "https://www.patreon.com/my-account"
  }
]

Users can use the npm fund subcommand to list the funding URLs of all dependencies of their project, direct and indirect. A shortcut to visit each funding url is also available when providing the project name such as: npm fund <projectname> (when there are multiple URLs, the first one will be visited)

files

The optional files field is an array of file patterns that describes the entries to be included when your package is installed as a dependency. File patterns follow a similar syntax to .gitignore, but reversed: including a file, directory, or glob pattern (*, **/*, and such) will make it so that file is included in the tarball when it's packed. Omitting the field will make it default to ["*"], which means it will include all files.

Some special files and directories are also included or excluded regardless of whether they exist in the files array (see below).

You can also provide a .npmignore file in the root of your package or in subdirectories, which will keep files from being included. At the root of your package it will not override the "files" field, but in subdirectories it will. The .npmignore file works just like a .gitignore. If there is a .gitignore file, and .npmignore is missing, .gitignore's contents will be used instead.

Files included with the "package.json#files" field cannot be excluded through .npmignore or .gitignore.

Certain files are always included, regardless of settings:

  • package.json
  • README
  • CHANGES / CHANGELOG / HISTORY
  • LICENSE / LICENCE
  • NOTICE
  • The file in the "main" field

README, CHANGES, LICENSE & NOTICE can have any case and extension.

Conversely, some files are always ignored:

  • .git
  • CVS
  • .svn
  • .hg
  • .lock-wscript
  • .wafpickle-N
  • .DS_Store
  • npm-debug.log
  • .npmrc
  • node_modules
  • config.gypi
  • package-lock.json (use shrinkwrap instead)
  • All files containing a * character (incompatible with Windows)

main

The main field is a module ID that is the primary entry point to your program. That is, if your package is named foo, and a user installs it, and then does require("foo"), then your main module's exports object will be returned.

This should be a module ID relative to the root of your package folder.

For most modules, it makes the most sense to have a main script and often not much else.

browser

If your module is meant to be used client-side the browser field should be used instead of the main field. This is helpful to hint users that it might rely on primitives that aren't available in Node.js modules. (e.g. window)

bin

A lot of packages have one or more executable files that they'd like to install into the PATH. npm makes this pretty easy (in fact, it uses this feature to install the "npm" executable.)

To use this, supply a bin field in your package.json which is a map of command name to local file name. On install, npm will symlink that file into prefix/bin for global installs, or ./node_modules/.bin/ for local installs.

For example, myapp could have this:

{ "bin": { "myapp": "./cli.js" } }

So, when you install myapp, it'll create a symlink from the cli.js script to /usr/local/bin/myapp.

If you have a single executable, and its name should be the name of the package, then you can just supply it as a string. For example:

{ "name": "my-program", "version": "1.2.5", "bin": "./path/to/program" }

would be the same as this:

{
  "name": "my-program",
  "version": "1.2.5",
  "bin": { "my-program": "./path/to/program" }
}

Please make sure that your file(s) referenced in bin starts with #!/usr/bin/env node, otherwise the scripts are started without the node executable!

man

Specify either a single file or an array of filenames to put in place for the man program to find.

If only a single file is provided, then it's installed such that it is the result from man <pkgname>, regardless of its actual filename. For example:

{
  "name": "foo",
  "version": "1.2.3",
  "description": "A packaged foo fooer for fooing foos",
  "main": "foo.js",
  "man": "./man/doc.1"
}

would link the ./man/doc.1 file in such that it is the target for man foo

If the filename doesn't start with the package name, then it's prefixed. So, this:

{
  "name": "foo",
  "version": "1.2.3",
  "description": "A packaged foo fooer for fooing foos",
  "main": "foo.js",
  "man": ["./man/foo.1", "./man/bar.1"]
}

will create files to do man foo and man foo-bar.

Man files must end with a number, and optionally a .gz suffix if they are compressed. The number dictates which man section the file is installed into.

{
  "name": "foo",
  "version": "1.2.3",
  "description": "A packaged foo fooer for fooing foos",
  "main": "foo.js",
  "man": ["./man/foo.1", "./man/foo.2"]
}

will create entries for man foo and man 2 foo

directories

The CommonJS Packages spec details a few ways that you can indicate the structure of your package using a directories object. If you look at npm's package.json, you'll see that it has directories for doc, lib, and man.

In the future, this information may be used in other creative ways.

directories.lib

Tell people where the bulk of your library is. Nothing special is done with the lib folder in any way, but it's useful meta info.

directories.bin

If you specify a bin directory in directories.bin, all the files in that folder will be added.

Because of the way the bin directive works, specifying both a bin path and setting directories.bin is an error. If you want to specify individual files, use bin, and for all the files in an existing bin directory, use directories.bin.

directories.man

A folder that is full of man pages. Sugar to generate a "man" array by walking the folder.

directories.doc

Put markdown files in here. Eventually, these will be displayed nicely, maybe, someday.

directories.example

Put example scripts in here. Someday, it might be exposed in some clever way.

directories.test

Put your tests in here. It is currently not exposed, but it might be in the future.

repository

Specify the place where your code lives. This is helpful for people who want to contribute. If the git repo is on GitHub, then the npm docs command will be able to find you.

Do it like this:

"repository": {
  "type" : "git",
  "url" : "https://github.com/npm/cli.git"
}

"repository": {
  "type" : "svn",
  "url" : "https://v8.googlecode.com/svn/trunk/"
}

The URL should be a publicly available (perhaps read-only) url that can be handed directly to a VCS program without any modification. It should not be a url to an html project page that you put in your browser. It's for computers.

For GitHub, GitHub gist, Bitbucket, or GitLab repositories you can use the same shortcut syntax you use for npm install:

"repository": "npm/npm"

"repository": "github:user/repo"

"repository": "gist:11081aaa281"

"repository": "bitbucket:user/repo"

"repository": "gitlab:user/repo"

If the package.json for your package is not in the root directory (for example if it is part of a monorepo), you can specify the directory in which it lives:

"repository": {
  "type" : "git",
  "url" : "https://github.com/facebook/react.git",
  "directory": "packages/react-dom"
}

scripts

The "scripts" property is a dictionary containing script commands that are run at various times in the lifecycle of your package. The key is the lifecycle event, and the value is the command to run at that point.

See scripts to find out more about writing package scripts.

config

A "config" object can be used to set configuration parameters used in package scripts that persist across upgrades. For instance, if a package had the following:

{ "name": "foo", "config": { "port": "8080" } }

and then had a "start" command that then referenced the npm_package_config_port environment variable, then the user could override that by doing npm config set foo:port 8001.

See config and scripts for more on package configs.

dependencies

Dependencies are specified in a simple object that maps a package name to a version range. The version range is a string which has one or more space-separated descriptors. Dependencies can also be identified with a tarball or git URL.

Please do not put test harnesses or transpilers in your dependencies object. See devDependencies, below.

See semver for more details about specifying version ranges.

  • version Must match version exactly
  • >version Must be greater than version
  • >=version etc
  • <version
  • <=version
  • ~version "Approximately equivalent to version" See semver
  • ^version "Compatible with version" See semver
  • 1.2.x 1.2.0, 1.2.1, etc., but not 1.3.0
  • http://... See 'URLs as Dependencies' below
  • * Matches any version
  • "" (just an empty string) Same as *
  • version1 - version2 Same as >=version1 <=version2.
  • range1 || range2 Passes if either range1 or range2 are satisfied.
  • git... See 'Git URLs as Dependencies' below
  • user/repo See 'GitHub URLs' below
  • tag A specific version tagged and published as tag See npm dist-tag
  • path/path/path See Local Paths below

For example, these are all valid:

{
  "dependencies": {
    "foo": "1.0.0 - 2.9999.9999",
    "bar": ">=1.0.2 <2.1.2",
    "baz": ">1.0.2 <=2.3.4",
    "boo": "2.0.1",
    "qux": "<1.0.0 || >=2.3.1 <2.4.5 || >=2.5.2 <3.0.0",
    "asd": "http://asdf.com/asdf.tar.gz",
    "til": "~1.2",
    "elf": "~1.2.3",
    "two": "2.x",
    "thr": "3.3.x",
    "lat": "latest",
    "dyl": "file:../dyl"
  }
}

URLs as Dependencies

You may specify a tarball URL in place of a version range.

This tarball will be downloaded and installed locally to your package at install time.

Git URLs as Dependencies

Git urls are of the form:

<protocol>://[<user>[:<password>]@]<hostname>[:<port>][:][/]<path>[#<commit-ish> | #semver:<semver>]

<protocol> is one of git, git+ssh, git+http, git+https, or git+file.

If #<commit-ish> is provided, it will be used to clone exactly that commit. If the commit-ish has the format #semver:<semver>, <semver> can be any valid semver range or exact version, and npm will look for any tags or refs matching that range in the remote repository, much as it would for a registry dependency. If neither #<commit-ish> or #semver:<semver> is specified, then master is used.

Examples:

git+ssh://git@github.com:npm/cli.git#v1.0.27
git+ssh://git@github.com:npm/cli#semver:^5.0
git+https://isaacs@github.com/npm/cli.git
git://github.com/npm/cli.git#v1.0.27

GitHub URLs

As of version 1.1.65, you can refer to GitHub urls as just "foo": "user/foo-project". Just as with git URLs, a commit-ish suffix can be included. For example:

{
  "name": "foo",
  "version": "0.0.0",
  "dependencies": {
    "express": "expressjs/express",
    "mocha": "mochajs/mocha#4727d357ea",
    "module": "user/repo#feature/branch"
  }
}

Local Paths

As of version 2.0.0 you can provide a path to a local directory that contains a package. Local paths can be saved using npm install -S or npm install --save, using any of these forms:

../foo/bar
~/foo/bar
./foo/bar
/foo/bar

in which case they will be normalized to a relative path and added to your package.json. For example:

{
  "name": "baz",
  "dependencies": {
    "bar": "file:../foo/bar"
  }
}

This feature is helpful for local offline development and creating tests that require npm installing where you don't want to hit an external server, but should not be used when publishing packages to the public registry.

devDependencies

If someone is planning on downloading and using your module in their program, then they probably don't want or need to download and build the external test or documentation framework that you use.

In this case, it's best to map these additional items in a devDependencies object.

These things will be installed when doing npm link or npm install from the root of a package, and can be managed like any other npm configuration param. See config for more on the topic.

For build steps that are not platform-specific, such as compiling CoffeeScript or other languages to JavaScript, use the prepare script to do this, and make the required package a devDependency.

For example:

{
  "name": "ethopia-waza",
  "description": "a delightfully fruity coffee varietal",
  "version": "1.2.3",
  "devDependencies": {
    "coffee-script": "~1.6.3"
  },
  "scripts": {
    "prepare": "coffee -o lib/ -c src/waza.coffee"
  },
  "main": "lib/waza.js"
}

The prepare script will be run before publishing, so that users can consume the functionality without requiring them to compile it themselves. In dev mode (ie, locally running npm install), it'll run this script as well, so that you can test it easily.

peerDependencies

In some cases, you want to express the compatibility of your package with a host tool or library, while not necessarily doing a require of this host. This is usually referred to as a plugin. Notably, your module may be exposing a specific interface, expected and specified by the host documentation.

For example:

{
  "name": "tea-latte",
  "version": "1.3.5",
  "peerDependencies": {
    "tea": "2.x"
  }
}

This ensures your package tea-latte can be installed along with the second major version of the host package tea only. npm install tea-latte could possibly yield the following dependency graph:

├── tea-latte@1.3.5
└── tea@2.2.0

NOTE: npm versions 1 and 2 will automatically install peerDependencies if they are not explicitly depended upon higher in the dependency tree. In the next major version of npm (npm@3), this will no longer be the case. You will receive a warning that the peerDependency is not installed instead. The behavior in npms 1 & 2 was frequently confusing and could easily put you into dependency hell, a situation that npm is designed to avoid as much as possible.

Trying to install another plugin with a conflicting requirement will cause an error. For this reason, make sure your plugin requirement is as broad as possible, and not to lock it down to specific patch versions.

Assuming the host complies with semver, only changes in the host package's major version will break your plugin. Thus, if you've worked with every 1.x version of the host package, use "^1.0" or "1.x" to express this. If you depend on features introduced in 1.5.2, use ">= 1.5.2 < 2".

bundledDependencies

This defines an array of package names that will be bundled when publishing the package.

In cases where you need to preserve npm packages locally or have them available through a single file download, you can bundle the packages in a tarball file by specifying the package names in the bundledDependencies array and executing npm pack.

For example:

If we define a package.json like this:

{
  "name": "awesome-web-framework",
  "version": "1.0.0",
  "bundledDependencies": ["renderized", "super-streams"]
}

we can obtain awesome-web-framework-1.0.0.tgz file by running npm pack. This file contains the dependencies renderized and super-streams which can be installed in a new project by executing npm install awesome-web-framework-1.0.0.tgz. Note that the package names do not include any versions, as that information is specified in dependencies.

If this is spelled "bundleDependencies", then that is also honored.

optionalDependencies

If a dependency can be used, but you would like npm to proceed if it cannot be found or fails to install, then you may put it in the optionalDependencies object. This is a map of package name to version or url, just like the dependencies object. The difference is that build failures do not cause installation to fail. Running npm install --no-optional will prevent these dependencies from being installed.

It is still your program's responsibility to handle the lack of the dependency. For example, something like this:

try {
  var foo = require("foo");
  var fooVersion = require("foo/package.json").version;
} catch (er) {
  foo = null;
}
if (notGoodFooVersion(fooVersion)) {
  foo = null;
}

// .. then later in your program ..

if (foo) {
  foo.doFooThings();
}

Entries in optionalDependencies will override entries of the same name in dependencies, so it's usually best to only put in one place.

engines

You can specify the version of node that your stuff works on:

{ "engines": { "node": ">=0.10.3 <0.12" } }

And, like with dependencies, if you don't specify the version (or if you specify "*" as the version), then any version of node will do.

If you specify an "engines" field, then npm will require that "node" be somewhere on that list. If "engines" is omitted, then npm will just assume that it works on node.

You can also use the "engines" field to specify which versions of npm are capable of properly installing your program. For example:

{ "engines": { "npm": "~1.0.20" } }

Unless the user has set the engine-strict config flag, this field is advisory only and will only produce warnings when your package is installed as a dependency.

engineStrict

This feature was removed in npm 3.0.0

Prior to npm 3.0.0, this feature was used to treat this package as if the user had set engine-strict. It is no longer used.

os

You can specify which operating systems your module will run on:

"os" : [ "darwin", "linux" ]

You can also blacklist instead of whitelist operating systems, just prepend the blacklisted os with a '!':

"os" : [ "!win32" ]

The host operating system is determined by process.platform

It is allowed to both blacklist, and whitelist, although there isn't any good reason to do this.

cpu

If your code only runs on certain cpu architectures, you can specify which ones.

"cpu" : [ "x64", "ia32" ]

Like the os option, you can also blacklist architectures:

"cpu" : [ "!arm", "!mips" ]

The host architecture is determined by process.arch

preferGlobal

DEPRECATED

This option used to trigger an npm warning, but it will no longer warn. It is purely there for informational purposes. It is now recommended that you install any binaries as local devDependencies wherever possible.

private

If you set "private": true in your package.json, then npm will refuse to publish it.

This is a way to prevent accidental publication of private repositories. If you would like to ensure that a given package is only ever published to a specific registry (for example, an internal registry), then use the publishConfig dictionary described below to override the registry config param at publish-time.

publishConfig

This is a set of config values that will be used at publish-time. It's especially handy if you want to set the tag, registry or access, so that you can ensure that a given package is not tagged with "latest", published to the global public registry or that a scoped module is private by default.

Any config values can be overridden, but only "tag", "registry" and "access" probably matter for the purposes of publishing.

See config to see the list of config options that can be overridden.

DEFAULT VALUES

npm will default some values based on package contents.

  • "scripts": {"start": "node server.js"}

    If there is a server.js file in the root of your package, then npm will default the start command to node server.js.

  • "scripts":{"install": "node-gyp rebuild"}

    If there is a binding.gyp file in the root of your package and you have not defined an install or preinstall script, npm will default the install command to compile using node-gyp.

  • "contributors": [...]

    If there is an AUTHORS file in the root of your package, npm will treat each line as a Name <email> (url) format, where email and url are optional. Lines which start with a # or are blank, will be ignored.

SEE ALSO

section: configuring-npm title: package-lock.json description: A manifestation of the manifest

package-lock.json(5)

A manifestation of the manifest

Description

package-lock.json is automatically generated for any operations where npm modifies either the node_modules tree, or package.json. It describes the exact tree that was generated, such that subsequent installs are able to generate identical trees, regardless of intermediate dependency updates.

This file is intended to be committed into source repositories, and serves various purposes:

  • Describe a single representation of a dependency tree such that teammates, deployments, and continuous integration are guaranteed to install exactly the same dependencies.

  • Provide a facility for users to "time-travel" to previous states of node_modules without having to commit the directory itself.

  • To facilitate greater visibility of tree changes through readable source control diffs.

  • And optimize the installation process by allowing npm to skip repeated metadata resolutions for previously-installed packages.

One key detail about package-lock.json is that it cannot be published, and it will be ignored if found in any place other than the toplevel package. It shares a format with npm-shrinkwrap.json, which is essentially the same file, but allows publication. This is not recommended unless deploying a CLI tool or otherwise using the publication process for producing production packages.

If both package-lock.json and npm-shrinkwrap.json are present in the root of a package, package-lock.json will be completely ignored.

File Format

name

The name of the package this is a package-lock for. This must match what's in package.json.

version

The version of the package this is a package-lock for. This must match what's in package.json.

lockfileVersion

An integer version, starting at 1 with the version number of this document whose semantics were used when generating this package-lock.json.

packageIntegrity

This is a subresource integrity value created from the package.json. No preprocessing of the package.json should be done. Subresource integrity strings can be produced by modules like ssri.

preserveSymlinks

Indicates that the install was done with the environment variable NODE_PRESERVE_SYMLINKS enabled. The installer should insist that the value of this property match that environment variable.

dependencies

A mapping of package name to dependency object. Dependency objects have the following properties:

version

This is a specifier that uniquely identifies this package and should be usable in fetching a new copy of it.

  • bundled dependencies: Regardless of source, this is a version number that is purely for informational purposes.
  • registry sources: This is a version number. (eg, 1.2.3)
  • git sources: This is a git specifier with resolved committish. (eg, git+https://example.com/foo/bar#115311855adb0789a0466714ed48a1499ffea97e)
  • http tarball sources: This is the URL of the tarball. (eg, https://example.com/example-1.3.0.tgz)
  • local tarball sources: This is the file URL of the tarball. (eg file:///opt/storage/example-1.3.0.tgz)
  • local link sources: This is the file URL of the link. (eg file:libs/our-module)
integrity

This is a Standard Subresource Integrity for this resource.

  • For bundled dependencies this is not included, regardless of source.
  • For registry sources, this is the integrity that the registry provided, or if one wasn't provided the SHA1 in shasum.
  • For git sources this is the specific commit hash we cloned from.
  • For remote tarball sources this is an integrity based on a SHA512 of the file.
  • For local tarball sources: This is an integrity field based on the SHA512 of the file.
resolved
  • For bundled dependencies this is not included, regardless of source.
  • For registry sources this is path of the tarball relative to the registry URL. If the tarball URL isn't on the same server as the registry URL then this is a complete URL.
bundled

If true, this is the bundled dependency and will be installed by the parent module. When installing, this module will be extracted from the parent module during the extract phase, not installed as a separate dependency.

dev

If true then this dependency is either a development dependency ONLY of the top level module or a transitive dependency of one. This is false for dependencies that are both a development dependency of the top level and a transitive dependency of a non-development dependency of the top level.

optional

If true then this dependency is either an optional dependency ONLY of the top level module or a transitive dependency of one. This is false for dependencies that are both an optional dependency of the top level and a transitive dependency of a non-optional dependency of the top level.

All optional dependencies should be included even if they're uninstallable on the current platform.

requires

This is a mapping of module name to version. This is a list of everything this module requires, regardless of where it will be installed. The version should match via normal matching rules a dependency either in our dependencies or in a level higher than us.

dependencies

The dependencies of this dependency, exactly as at the top level.

See also

section: configuring-npm title: package-locks description: An explanation of npm lockfiles

package-locks(5)

An explanation of npm lockfiles

Description

Conceptually, the "input" to npm install is a package.json, while its "output" is a fully-formed node_modules tree: a representation of the dependencies you declared. In an ideal world, npm would work like a pure function: the same package.json should produce the exact same node_modules tree, any time. In some cases, this is indeed true. But in many others, npm is unable to do this. There are multiple reasons for this:

  • different versions of npm (or other package managers) may have been used to install a package, each using slightly different installation algorithms.

  • a new version of a direct semver-range package may have been published since the last time your packages were installed, and thus a newer version will be used.

  • A dependency of one of your dependencies may have published a new version, which will update even if you used pinned dependency specifiers (1.2.3 instead of ^1.2.3)

  • The registry you installed from is no longer available, or allows mutation of versions (unlike the primary npm registry), and a different version of a package exists under the same version number now.

As an example, consider package A:

{
  "name": "A",
  "version": "0.1.0",
  "dependencies": {
    "B": "<0.1.0"
  }
}

package B:

{
  "name": "B",
  "version": "0.0.1",
  "dependencies": {
    "C": "<0.1.0"
  }
}

and package C:

{
  "name": "C",
  "version": "0.0.1"
}

If these are the only versions of A, B, and C available in the registry, then a normal npm install A will install:

A@0.1.0
`-- B@0.0.1
    `-- C@0.0.1

However, if B@0.0.2 is published, then a fresh npm install A will install:

A@0.1.0
`-- B@0.0.2
    `-- C@0.0.1

assuming the new version did not modify B's dependencies. Of course, the new version of B could include a new version of C and any number of new dependencies. If such changes are undesirable, the author of A could specify a dependency on B@0.0.1. However, if A's author and B's author are not the same person, there's no way for A's author to say that he or she does not want to pull in newly published versions of C when B hasn't changed at all.

To prevent this potential issue, npm uses package-lock.json or, if present, npm-shrinkwrap.json. These files are called package locks, or lockfiles.

Whenever you run npm install, npm generates or updates your package lock, which will look something like this:

{
  "name": "A",
  "version": "0.1.0",
  ...metadata fields...
  "dependencies": {
    "B": {
      "version": "0.0.1",
      "resolved": "https://registry.npmjs.org/B/-/B-0.0.1.tgz",
      "integrity": "sha512-DeAdb33F+"
      "dependencies": {
        "C": {
          "version": "git://github.com/org/C.git#5c380ae319fc4efe9e7f2d9c78b0faa588fd99b4"
        }
      }
    }
  }
}

This file describes an exact, and more importantly reproducible node_modules tree. Once it's present, any future installation will base its work off this file, instead of recalculating dependency versions off package.json.

The presence of a package lock changes the installation behavior such that:

  1. The module tree described by the package lock is reproduced. This means reproducing the structure described in the file, using the specific files referenced in "resolved" if available, falling back to normal package resolution using "version" if one isn't.

  2. The tree is walked and any missing dependencies are installed in the usual fashion.

If preshrinkwrap, shrinkwrap or postshrinkwrap are in the scripts property of the package.json, they will be executed in order. preshrinkwrap and shrinkwrap are executed before the shrinkwrap, postshrinkwrap is executed afterwards. These scripts run for both package-lock.json and npm-shrinkwrap.json. For example to run some postprocessing on the generated file:

  "scripts": {
    "postshrinkwrap": "json -I -e \"this.myMetadata = $MY_APP_METADATA\""
  }

Using locked packages

Using a locked package is no different than using any package without a package lock: any commands that update node_modules and/or package.json's dependencies will automatically sync the existing lockfile. This includes npm install, npm rm, npm update, etc. To prevent this update from happening, you can use the --no-save option to prevent saving altogether, or --no-shrinkwrap to allow package.json to be updated while leaving package-lock.json or npm-shrinkwrap.json intact.

It is highly recommended you commit the generated package lock to source control: this will allow anyone else on your team, your deployments, your CI/continuous integration, and anyone else who runs npm install in your package source to get the exact same dependency tree that you were developing on. Additionally, the diffs from these changes are human-readable and will inform you of any changes npm has made to your node_modules, so you can notice if any transitive dependencies were updated, hoisted, etc.

Resolving lockfile conflicts

Occasionally, two separate npm install will create package locks that cause merge conflicts in source control systems. As of npm@5.7.0, these conflicts can be resolved by manually fixing any package.json conflicts, and then running npm install [--package-lock-only] again. npm will automatically resolve any conflicts for you and write a merged package lock that includes all the dependencies from both branches in a reasonable tree. If --package-lock-only is provided, it will do this without also modifying your local node_modules/.

To make this process seamless on git, consider installing npm-merge-driver, which will teach git how to do this itself without any user interaction. In short: $ npx npm-merge-driver install -g will let you do this, and even works with pre-npm@5.7.0 versions of npm 5, albeit a bit more noisily. Note that if package.json itself conflicts, you will have to resolve that by hand and run npm install manually, even with the merge driver.

See Also

section: configuring-npm title: shrinkwrap.json description: A publishable lockfile

npm-shrinkwrap.json(5)

A publishable lockfile

Description

npm-shrinkwrap.json is a file created by npm shrinkwrap. It is identical to package-lock.json, with one major caveat: Unlike package-lock.json, npm-shrinkwrap.json may be included when publishing a package.

The recommended use-case for npm-shrinkwrap.json is applications deployed through the publishing process on the registry: for example, daemons and command-line tools intended as global installs or devDependencies. It's strongly discouraged for library authors to publish this file, since that would prevent end users from having control over transitive dependency updates.

Additionally, if both package-lock.json and npm-shrinkwrap.json are present in a package root, package-lock.json will be ignored in favor of this file.

For full details and description of the npm-shrinkwrap.json file format, refer to the manual page for package-lock.json.

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