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1 ---
2 title: package.json
3 section: 5
4 description: Specifics of npm's package.json handling
5 github_repo: npm/cli
6 github_branch: latest
7 github_path: docs/lib/content/configuring-npm/package-json.md
8 redirect_from:
9 - /cli-documentation/configuring-npm/package-json
10 - /cli-documentation/configuring-npm/package.json
11 - /cli-documentation/files/package-json
12 - /cli-documentation/files/package.json
13 - /cli-documentation/v11/configuring-npm/package-json
14 - /cli-documentation/v11/configuring-npm/package.json
15 - /cli-documentation/v11/files/package-json
16 - /cli-documentation/v11/files/package.json
17 - /cli/configuring-npm/package-json
18 - /cli/configuring-npm/package.json
19 - /cli/files/package-json
20 - /cli/files/package.json
21 - /cli/v11/configuring-npm/package.json
22 - /cli/v11/files/package-json
23 - /cli/v11/files/package.json
24 - /configuring-npm/package-json
25 - /configuring-npm/package.json
26 - /files/package-json
27 - /files/package.json
28 ---
29
30 ### Description
31
32 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.
33
34 A lot of the behavior described in this document is affected by the config settings described in [`config`](/cli/v11/using-npm/config).
35
36 ### name
37
38 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.
39
40 The name is what your thing is called.
41
42 Some rules:
43
44 - The name must be less than or equal to 214 characters. This includes the scope for scoped packages.
45 - The names of scoped packages can begin with a dot or an underscore. This is not permitted without a scope.
46 - New packages must not have uppercase letters in the name.
47 - 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.
48
49 Some tips:
50
51 - Don't use the same name as a core Node module.
52 - 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](#engines)" field. (See below.)
53 - The name will probably be passed as an argument to require(), so it should be something short, but also reasonably descriptive.
54 - 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/](https://www.npmjs.com/)
55
56 A name can be optionally prefixed by a scope, e.g. `@npm/example`. See [`scope`](/cli/v11/using-npm/scope) for more detail.
57
58 ### version
59
60 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.
61
62 Version must be parseable by [node-semver](https://github.com/npm/node-semver), which is bundled with npm as a dependency. (`npm install semver` to use it yourself.)
63
64 ### description
65
66 Put a description in it. It's a string. This helps people discover your package, as it's listed in `npm search`.
67
68 ### keywords
69
70 Put keywords in it. It's an array of strings. This helps people discover your package as it's listed in `npm search`.
71
72 ### homepage
73
74 The URL to the project homepage.
75
76 Example:
77
78 ```json
79 "homepage": "https://github.com/npm/example#readme"
80 ```
81
82 ### bugs
83
84 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.
85
86 It should look like this:
87
88 ```json
89 {
90 "bugs": {
91 "url": "https://github.com/npm/example/issues",
92 "email": "example@npmjs.com"
93 }
94 }
95 ```
96
97 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.
98
99 If a URL is provided, it will be used by the `npm bugs` command.
100
101 ### license
102
103 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.
104
105 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:
106
107 ```json
108 {
109 "license": "BSD-3-Clause"
110 }
111 ```
112
113 You can check [the full list of SPDX license IDs](https://spdx.org/licenses/). Ideally, you should pick one that is [OSI](https://opensource.org/licenses/) approved.
114
115 If your package is licensed under multiple common licenses, use an [SPDX license expression syntax version 2.0 string](https://spdx.dev/specifications/), like this:
116
117 ```json
118 {
119 "license": "(ISC OR GPL-3.0)"
120 }
121 ```
122
123 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:
124
125 ```json
126 {
127 "license": "SEE LICENSE IN <filename>"
128 }
129 ```
130
131 Then include a file named `<filename>` at the top level of the package.
132
133 Some old packages used license objects or a "licenses" property containing an array of license objects:
134
135 ```json
136 // Not valid metadata
137 {
138 "license" : {
139 "type" : "ISC",
140 "url" : "https://opensource.org/licenses/ISC"
141 }
142 }
143
144 // Not valid metadata
145 {
146 "licenses" : [
147 {
148 "type": "MIT",
149 "url": "https://www.opensource.org/licenses/mit-license.php"
150 },
151 {
152 "type": "Apache-2.0",
153 "url": "https://opensource.org/licenses/apache2.0.php"
154 }
155 ]
156 }
157 ```
158
159 Those styles are now deprecated. Instead, use SPDX expressions, like this:
160
161 ```json
162 {
163 "license": "ISC"
164 }
165 ```
166
167 ```json
168 {
169 "license": "(MIT OR Apache-2.0)"
170 }
171 ```
172
173 Finally, if you do not wish to grant others the right to use a private or unpublished package under any terms:
174
175 ```json
176 {
177 "license": "UNLICENSED"
178 }
179 ```
180
181 Consider also setting `"private": true` to prevent accidental publication.
182
183 ### people fields: author, contributors
184
185 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:
186
187 ```json
188 {
189 "name": "Barney Rubble",
190 "email": "barney@npmjs.com",
191 "url": "http://barnyrubble.npmjs.com/"
192 }
193 ```
194
195 Or you can shorten that all into a single string, and npm will parse it for you:
196
197 ```json
198 {
199 "author": "Barney Rubble <barney@npmjs.com> (http://barnyrubble.npmjs.com/)"
200 }
201 ```
202
203 Both email and url are optional either way.
204
205 npm also sets a top-level "maintainers" field with your npm user info.
206
207 ### funding
208
209 You can specify an object containing a URL that provides up-to-date information about ways to help fund development of your package, a string URL, or an array of objects and string URLs:
210
211 ```json
212 {
213 "funding": {
214 "type": "individual",
215 "url": "http://npmjs.com/donate"
216 }
217 }
218 ```
219
220 ```json
221 {
222 "funding": {
223 "type": "patreon",
224 "url": "https://www.patreon.com/user"
225 }
226 }
227 ```
228
229 ```json
230 {
231 "funding": "http://npmjs.com/donate"
232 }
233 ```
234
235 ```json
236 {
237 "funding": [
238 {
239 "type": "individual",
240 "url": "http://npmjs.com/donate"
241 },
242 "http://npmjs.com/donate-also",
243 {
244 "type": "patreon",
245 "url": "https://www.patreon.com/user"
246 }
247 ]
248 }
249 ```
250
251 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)
252
253 ### files
254
255 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.
256
257 Some special files and directories are also included or excluded regardless of whether they exist in the `files` array (see below).
258
259 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.
260
261 Certain files are always included, regardless of settings:
262
263 - `package.json`
264 - `README`
265 - `LICENSE` / `LICENCE`
266 - The file in the "main" field
267 - The file(s) in the "bin" field
268
269 `README` & `LICENSE` can have any case and extension.
270
271 Some files are always ignored by default:
272
273 - `*.orig`
274 - `.*.swp`
275 - `.DS_Store`
276 - `._*`
277 - `.git`
278 - `.hg`
279 - `.lock-wscript`
280 - `.npmrc`
281 - `.svn`
282 - `.wafpickle-N`
283 - `CVS`
284 - `config.gypi`
285 - `node_modules`
286 - `npm-debug.log`
287 - `package-lock.json` (use [`npm-shrinkwrap.json`](/cli/v11/configuring-npm/npm-shrinkwrap-json) if you wish it to be published)
288 - `pnpm-lock.yaml`
289 - `yarn.lock`
290 - `bun.lockb`
291
292 Most of these ignored files can be included specifically if included in the `files` globs. Exceptions to this are:
293
294 - `.git`
295 - `.npmrc`
296 - `node_modules`
297 - `package-lock.json`
298 - `pnpm-lock.yaml`
299 - `yarn.lock`
300 - `bun.lockb`
301
302 These cannot be included.
303
304 ### exports
305
306 The "exports" provides a modern alternative to "main" allowing multiple entry points to be defined, conditional entry resolution support between environments, and preventing any other entry points besides those defined in "exports". This encapsulation allows module authors to clearly define the public interface for their package. For more details see the [node.js documentation on package entry points](https://nodejs.org/api/packages.html#package-entry-points)
307
308 ### main
309
310 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.
311
312 This should be a module relative to the root of your package folder.
313
314 For most modules, it makes the most sense to have a main script and often not much else.
315
316 If `main` is not set, it defaults to `index.js` in the package's root folder.
317
318 ### browser
319
320 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`)
321
322 ### bin
323
324 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.)
325
326 To use this, supply a `bin` field in your package.json which is a map of command name to local file name. When this package is installed globally, that file will be either linked inside the global bins directory or a cmd (Windows Command File) will be created which executes the specified file in the `bin` field, so it is available to run by `name` or `name.cmd` (on Windows PowerShell). When this package is installed as a dependency in another package, the file will be linked where it will be available to that package either directly by `npm exec` or by name in other scripts when invoking them via `npm run`.
327
328 For example, myapp could have this:
329
330 ```json
331 {
332 "bin": {
333 "myapp": "bin/cli.js"
334 }
335 }
336 ```
337
338 So, when you install myapp, in case of unix-like OS it'll create a symlink from the `cli.js` script to `/usr/local/bin/myapp` and in case of windows it will create a cmd file usually at `C:\Users\{Username}\AppData\Roaming\npm\myapp.cmd` which runs the `cli.js` script.
339
340 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:
341
342 ```json
343 {
344 "name": "my-program",
345 "version": "1.2.5",
346 "bin": "path/to/program"
347 }
348 ```
349
350 would be the same as this:
351
352 ```json
353 {
354 "name": "my-program",
355 "version": "1.2.5",
356 "bin": {
357 "my-program": "path/to/program"
358 }
359 }
360 ```
361
362 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!
363
364 Note that you can also set the executable files using [directories.bin](#directoriesbin).
365
366 See [folders](/cli/v11/configuring-npm/folders#executables) for more info on executables.
367
368 ### man
369
370 Specify either a single file or an array of filenames to put in place for the `man` program to find.
371
372 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:
373
374 ```json
375 {
376 "name": "foo",
377 "version": "1.2.3",
378 "description": "A packaged foo fooer for fooing foos",
379 "main": "foo.js",
380 "man": "./man/doc.1"
381 }
382 ```
383
384 would link the `./man/doc.1` file in such that it is the target for `man foo`
385
386 If the filename doesn't start with the package name, then it's prefixed. So, this:
387
388 ```json
389 {
390 "name": "foo",
391 "version": "1.2.3",
392 "description": "A packaged foo fooer for fooing foos",
393 "main": "foo.js",
394 "man": ["./man/foo.1", "./man/bar.1"]
395 }
396 ```
397
398 will create files to do `man foo` and `man foo-bar`.
399
400 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.
401
402 ```json
403 {
404 "name": "foo",
405 "version": "1.2.3",
406 "description": "A packaged foo fooer for fooing foos",
407 "main": "foo.js",
408 "man": ["./man/foo.1", "./man/foo.2"]
409 }
410 ```
411
412 will create entries for `man foo` and `man 2 foo`
413
414 ### directories
415
416 The CommonJS [Packages](http://wiki.commonjs.org/wiki/Packages/1.0) 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](https://registry.npmjs.org/npm/latest), you'll see that it has directories for doc, lib, and man.
417
418 In the future, this information may be used in other creative ways.
419
420 #### directories.bin
421
422 If you specify a `bin` directory in `directories.bin`, all the files in that folder will be added.
423
424 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`.
425
426 #### directories.man
427
428 A folder that is full of man pages. Sugar to generate a "man" array by walking the folder.
429
430 ### repository
431
432 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 repo` command will be able to find you.
433
434 Do it like this:
435
436 ```json
437 {
438 "repository": {
439 "type": "git",
440 "url": "git+https://github.com/npm/cli.git"
441 }
442 }
443 ```
444
445 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.
446
447 For GitHub, GitHub gist, Bitbucket, or GitLab repositories you can use the same shortcut syntax you use for `npm install`:
448
449 ```json
450 {
451 "repository": "npm/example",
452
453 "repository": "github:npm/example",
454
455 "repository": "gist:11081aaa281",
456
457 "repository": "bitbucket:user/repo",
458
459 "repository": "gitlab:user/repo"
460 }
461 ```
462
463 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:
464
465 ```json
466 {
467 "repository": {
468 "type": "git",
469 "url": "git+https://github.com/npm/cli.git",
470 "directory": "workspaces/libnpmpublish"
471 }
472 }
473 ```
474
475 ### scripts
476
477 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.
478
479 See [`scripts`](/cli/v11/using-npm/scripts) to find out more about writing package scripts.
480
481 ### config
482
483 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:
484
485 ```json
486 {
487 "name": "foo",
488 "config": {
489 "port": "8080"
490 }
491 }
492 ```
493
494 It could also have a "start" script that referenced the `npm_package_config_port` environment variable.
495
496 ### dependencies
497
498 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.
499
500 **Please do not put test harnesses or transpilers or other "development" time tools in your `dependencies` object.** See `devDependencies`, below.
501
502 See [semver](https://github.com/npm/node-semver#versions) for more details about specifying version ranges.
503
504 - `version` Must match `version` exactly
505 - `>version` Must be greater than `version`
506 - `>=version` etc
507 - `<version`
508 - `<=version`
509 - `~version` "Approximately equivalent to version" See [semver](https://github.com/npm/node-semver#versions)
510 - `^version` "Compatible with version" See [semver](https://github.com/npm/node-semver#versions)
511 - `1.2.x` 1.2.0, 1.2.1, etc., but not 1.3.0
512 - `http://...` See 'URLs as Dependencies' below
513 - `*` Matches any version
514 - `""` (just an empty string) Same as `*`
515 - `version1 - version2` Same as `>=version1 <=version2`.
516 - `range1 || range2` Passes if either range1 or range2 are satisfied.
517 - `git...` See 'Git URLs as Dependencies' below
518 - `user/repo` See 'GitHub URLs' below
519 - `tag` A specific version tagged and published as `tag` See [`npm dist-tag`](/cli/v11/commands/npm-dist-tag)
520 - `path/path/path` See [Local Paths](#local-paths) below
521 - `npm:@scope/pkg@version` Custom alias for a package See [`package-spec`](/cli/v11/using-npm/package-spec#aliases)
522
523 For example, these are all valid:
524
525 ```json
526 {
527 "dependencies": {
528 "foo": "1.0.0 - 2.9999.9999",
529 "bar": ">=1.0.2 <2.1.2",
530 "baz": ">1.0.2 <=2.3.4",
531 "boo": "2.0.1",
532 "qux": "<1.0.0 || >=2.3.1 <2.4.5 || >=2.5.2 <3.0.0",
533 "asd": "http://npmjs.com/example.tar.gz",
534 "til": "~1.2",
535 "elf": "~1.2.3",
536 "two": "2.x",
537 "thr": "3.3.x",
538 "lat": "latest",
539 "dyl": "file:../dyl",
540 "kpg": "npm:pkg@1.0.0"
541 }
542 }
543 ```
544
545 #### URLs as Dependencies
546
547 You may specify a tarball URL in place of a version range.
548
549 This tarball will be downloaded and installed locally to your package at install time.
550
551 #### Git URLs as Dependencies
552
553 Git URLs are of the form:
554
555 ```bash
556 <protocol>://[<user>[:<password>]@]<hostname>[:<port>][:][/]<path>[#<commit-ish> | #semver:<semver>]
557 ```
558
559 `<protocol>` is one of `git`, `git+ssh`, `git+http`, `git+https`, or `git+file`.
560
561 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 the default branch is used.
562
563 Examples:
564
565 ```bash
566 git+ssh://git@github.com:npm/cli.git#v1.0.27
567 git+ssh://git@github.com:npm/cli#semver:^5.0
568 git+https://isaacs@github.com/npm/cli.git
569 git://github.com/npm/cli.git#v1.0.27
570 ```
571
572 When installing from a `git` repository, the presence of certain fields in the `package.json` will cause npm to believe it needs to perform a build. To do so your repository will be cloned into a temporary directory, all of its deps installed, relevant scripts run, and the resulting directory packed and installed.
573
574 This flow will occur if your git dependency uses `workspaces`, or if any of the following scripts are present:
575
576 - `build`
577 - `prepare`
578 - `prepack`
579 - `preinstall`
580 - `install`
581 - `postinstall`
582
583 If your git repository includes pre-built artifacts, you will likely want to make sure that none of the above scripts are defined, or your dependency will be rebuilt for every installation.
584
585 #### GitHub URLs
586
587 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:
588
589 ```json
590 {
591 "name": "foo",
592 "version": "0.0.0",
593 "dependencies": {
594 "express": "expressjs/express",
595 "mocha": "mochajs/mocha#4727d357ea",
596 "module": "npm/example-github-repo#feature\/branch"
597 }
598 }
599 ```
600
601 #### Local Paths
602
603 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:
604
605 ```bash
606 ../foo/bar
607 ~/foo/bar
608 ./foo/bar
609 /foo/bar
610 ```
611
612 in which case they will be normalized to a relative path and added to your `package.json`. For example:
613
614 ```json
615 {
616 "name": "baz",
617 "dependencies": {
618 "bar": "file:../foo/bar"
619 }
620 }
621 ```
622
623 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 your package to the public registry.
624
625 _note_: Packages linked by local path will not have their own dependencies installed when `npm install` is run. You must run `npm install` from inside the local path itself.
626
627 ### devDependencies
628
629 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.
630
631 In this case, it's best to map these additional items in a `devDependencies` object.
632
633 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`](/cli/v11/using-npm/config) for more on the topic.
634
635 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.
636
637 For example:
638
639 ```json
640 {
641 "name": "@npm/ethopia-waza",
642 "description": "a delightfully fruity coffee varietal",
643 "version": "1.2.3",
644 "devDependencies": {
645 "coffee-script": "~1.6.3"
646 },
647 "scripts": {
648 "prepare": "coffee -o lib/ -c src/waza.coffee"
649 },
650 "main": "lib/waza.js"
651 }
652 ```
653
654 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.
655
656 ### peerDependencies
657
658 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.
659
660 For example:
661
662 ```json
663 {
664 "name": "@npm/tea-latte",
665 "version": "1.3.5",
666 "peerDependencies": {
667 "@npm/tea": "2.x"
668 }
669 }
670 ```
671
672 This ensures your package `@npm/tea-latte` can be installed _along_ with the second major version of the host package `@npm/tea` only. `npm install tea-latte` could possibly yield the following dependency graph:
673
674 ```bash
675 ├── @npm/tea-latte@1.3.5
676 └── @npm/tea@2.2.0
677 ```
678
679 In npm versions 3 through 6, `peerDependencies` were not automatically installed, and would raise a warning if an invalid version of the peer dependency was found in the tree. As of npm v7, peerDependencies _are_ installed by default.
680
681 Trying to install another plugin with a conflicting requirement may cause an error if the tree cannot be resolved correctly. For this reason, make sure your plugin requirement is as broad as possible, and not to lock it down to specific patch versions.
682
683 Assuming the host complies with [semver](https://semver.org/), 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"`.
684
685 ### peerDependenciesMeta
686
687 The `peerDependenciesMeta` field serves to provide npm more information on how your peer dependencies are to be used. Specifically, it allows peer dependencies to be marked as optional. Npm will not automatically install optional peer dependencies. This allows you to integrate and interact with a variety of host packages without requiring all of them to be installed.
688
689 For example:
690
691 ```json
692 {
693 "name": "@npm/tea-latte",
694 "version": "1.3.5",
695 "peerDependencies": {
696 "@npm/tea": "2.x",
697 "@npm/soy-milk": "1.2"
698 },
699 "peerDependenciesMeta": {
700 "@npm/soy-milk": {
701 "optional": true
702 }
703 }
704 }
705 ```
706
707 ### bundleDependencies
708
709 This defines an array of package names that will be bundled when publishing the package.
710
711 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 `bundleDependencies` array and executing `npm pack`.
712
713 For example:
714
715 If we define a package.json like this:
716
717 ```json
718 {
719 "name": "@npm/awesome-web-framework",
720 "version": "1.0.0",
721 "bundleDependencies": ["@npm/renderized", "@npm/super-streams"]
722 }
723 ```
724
725 we can obtain `@npm/awesome-web-framework-1.0.0.tgz` file by running `npm pack`. This file contains the dependencies `@npm/renderized` and `@npm/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`.
726
727 If this is spelled `"bundledDependencies"`, then that is also honored.
728
729 Alternatively, `"bundleDependencies"` can be defined as a boolean value. A value of `true` will bundle all dependencies, a value of `false` will bundle none.
730
731 ### optionalDependencies
732
733 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 --omit=optional` will prevent these dependencies from being installed.
734
735 It is still your program's responsibility to handle the lack of the dependency. For example, something like this:
736
737 ```js
738 try {
739 var foo = require("@npm/foo");
740 var fooVersion = require("@npm/foo/package.json").version;
741 } catch (er) {
742 foo = null;
743 }
744 if (notGoodFooVersion(fooVersion)) {
745 foo = null;
746 }
747
748 // .. then later in your program ..
749
750 if (foo) {
751 foo.doFooThings();
752 }
753 ```
754
755 Entries in `optionalDependencies` will override entries of the same name in `dependencies`, so it's usually best to only put in one place.
756
757 ### overrides
758
759 If you need to make specific changes to dependencies of your dependencies, for example replacing the version of a dependency with a known security issue, replacing an existing dependency with a fork, or making sure that the same version of a package is used everywhere, then you may add an override.
760
761 Overrides provide a way to replace a package in your dependency tree with another version, or another package entirely. These changes can be scoped as specific or as vague as desired.
762
763 Overrides are only considered in the root `package.json` file for a project. Overrides in installed dependencies (including [workspaces](/cli/v11/using-npm/workspaces)) are not considered in dependency tree resolution. Published packages may dictate their resolutions by pinning dependencies or using an [`npm-shrinkwrap.json`](/cli/v11/configuring-npm/npm-shrinkwrap-json) file.
764
765 To make sure the package `@npm/foo` is always installed as version `1.0.0` no matter what version your dependencies rely on:
766
767 ```json
768 {
769 "overrides": {
770 "@npm/foo": "1.0.0"
771 }
772 }
773 ```
774
775 The above is a short hand notation, the full object form can be used to allow overriding a package itself as well as a child of the package. This will cause `@npm/foo` to always be `1.0.0` while also making `@npm/bar` at any depth beyond `@npm/foo` also `1.0.0`:
776
777 ```json
778 {
779 "overrides": {
780 "@npm/foo": {
781 ".": "1.0.0",
782 "@npm/bar": "1.0.0"
783 }
784 }
785 }
786 ```
787
788 To only override `@npm/foo` to be `1.0.0` when it's a child (or grandchild, or great grandchild, etc) of the package `@npm/bar`:
789
790 ```json
791 {
792 "overrides": {
793 "@npm/bar": {
794 "@npm/foo": "1.0.0"
795 }
796 }
797 }
798 ```
799
800 Keys can be nested to any arbitrary length. To override `@npm/foo` only when it's a child of `@npm/bar` and only when `@npm/bar` is a child of `@npm/baz`:
801
802 ```json
803 {
804 "overrides": {
805 "@npm/baz": {
806 "@npm/bar": {
807 "@npm/foo": "1.0.0"
808 }
809 }
810 }
811 }
812 ```
813
814 The key of an override can also include a version, or range of versions. To override `@npm/foo` to `1.0.0`, but only when it's a child of `@npm/bar@2.0.0`:
815
816 ```json
817 {
818 "overrides": {
819 "@npm/bar@2.0.0": {
820 "@npm/foo": "1.0.0"
821 }
822 }
823 }
824 ```
825
826 You may not set an override for a package that you directly depend on unless both the dependency and the override itself share the exact same spec. To make this limitation easier to deal with, overrides may also be defined as a reference to a spec for a direct dependency by prefixing the name of the package you wish the version to match with a `$`.
827
828 ```json
829 {
830 "dependencies": {
831 "@npm/foo": "^1.0.0"
832 },
833 "overrides": {
834 // BAD, will throw an EOVERRIDE error
835 // "foo": "^2.0.0"
836 // GOOD, specs match so override is allowed
837 // "foo": "^1.0.0"
838 // BEST, the override is defined as a reference to the dependency
839 "@npm/foo": "$foo",
840 // the referenced package does not need to match the overridden one
841 "@npm/bar": "$foo"
842 }
843 }
844 ```
845
846 ### engines
847
848 You can specify the version of node that your stuff works on:
849
850 ```json
851 {
852 "engines": {
853 "node": ">=0.10.3 <15"
854 }
855 }
856 ```
857
858 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.
859
860 You can also use the "engines" field to specify which versions of npm are capable of properly installing your program. For example:
861
862 ```json
863 {
864 "engines": {
865 "npm": "~1.0.20"
866 }
867 }
868 ```
869
870 Unless the user has set the [`engine-strict` config](/cli/v11/using-npm/config#engine-strict) flag, this field is advisory only and will only produce warnings when your package is installed as a dependency.
871
872 ### os
873
874 You can specify which operating systems your module will run on:
875
876 ```json
877 {
878 "os": ["darwin", "linux"]
879 }
880 ```
881
882 You can also block instead of allowing operating systems, just prepend the blocked os with a '!':
883
884 ```json
885 {
886 "os": ["!win32"]
887 }
888 ```
889
890 The host operating system is determined by `process.platform`
891
892 It is allowed to both block and allow an item, although there isn't any good reason to do this.
893
894 ### cpu
895
896 If your code only runs on certain cpu architectures, you can specify which ones.
897
898 ```json
899 {
900 "cpu": ["x64", "ia32"]
901 }
902 ```
903
904 Like the `os` option, you can also block architectures:
905
906 ```json
907 {
908 "cpu": ["!arm", "!mips"]
909 }
910 ```
911
912 The host architecture is determined by `process.arch`
913
914 ### libc
915
916 If your code only runs or builds in certain versions of libc, you can specify which ones. This field only applies if `os` is `linux`.
917
918 ```json
919 {
920 "os": "linux",
921 "libc": "glibc"
922 }
923 ```
924
925 ### devEngines
926
927 The `devEngines` field aids engineers working on a codebase to all be using the same tooling.
928
929 You can specify a `devEngines` property in your `package.json` which will run before `install`, `ci`, and `run` commands.
930
931 > Note: `engines` and `devEngines` differ in object shape. They also function very differently. `engines` is designed to alert the user when a dependency uses a different npm or node version than the project it's being used in, whereas `devEngines` is used to alert people interacting with the source code of a project.
932
933 The supported keys under the `devEngines` property are `cpu`, `os`, `libc`, `runtime`, and `packageManager`. Each property can be an object or an array of objects. Objects must contain `name`, and optionally can specify `version`, and `onFail`. `onFail` can be `warn`, `error`, or `ignore`, and if left undefined is of the same value as `error`. `npm` will assume that you're running with `node`. Here's an example of a project that will fail if the environment is not `node` and `npm`. If you set `runtime.name` or `packageManager.name` to any other string, it will fail within the npm CLI.
934
935 ```json
936 {
937 "devEngines": {
938 "runtime": {
939 "name": "node",
940 "onFail": "error"
941 },
942 "packageManager": {
943 "name": "npm",
944 "onFail": "error"
945 }
946 }
947 }
948 ```
949
950 ### private
951
952 If you set `"private": true` in your package.json, then npm will refuse to publish it.
953
954 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.
955
956 ### publishConfig
957
958 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.
959
960 See [`config`](/cli/v11/using-npm/config) to see the list of config options that can be overridden.
961
962 ### workspaces
963
964 The optional `workspaces` field is an array of file patterns that describes locations within the local file system that the install client should look up to find each [workspace](/cli/v11/using-npm/workspaces) that needs to be symlinked to the top level `node_modules` folder.
965
966 It can describe either the direct paths of the folders to be used as workspaces or it can define globs that will resolve to these same folders.
967
968 In the following example, all folders located inside the folder `./packages` will be treated as workspaces as long as they have valid `package.json` files inside them:
969
970 ```json
971 {
972 "name": "workspace-example",
973 "workspaces": ["./packages/*"]
974 }
975 ```
976
977 See [`workspaces`](/cli/v11/using-npm/workspaces) for more examples.
978
979 ### DEFAULT VALUES
980
981 npm will default some values based on package contents.
982
983 - `"scripts": {"start": "node server.js"}`
984
985 If there is a `server.js` file in the root of your package, then npm will default the `start` command to `node server.js`.
986
987 - `"scripts":{"install": "node-gyp rebuild"}`
988
989 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.
990
991 - `"contributors": [...]`
992
993 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.
994
995 ### SEE ALSO
996
997 - [semver](https://github.com/npm/node-semver#versions)
998 - [workspaces](/cli/v11/using-npm/workspaces)
999 - [npm init](/cli/v11/commands/npm-init)
1000 - [npm version](/cli/v11/commands/npm-version)
1001 - [npm config](/cli/v11/commands/npm-config)
1002 - [npm help](/cli/v11/commands/npm-help)
1003 - [npm install](/cli/v11/commands/npm-install)
1004 - [npm publish](/cli/v11/commands/npm-publish)
1005 - [npm uninstall](/cli/v11/commands/npm-uninstall)