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 Example:
73
74 ```json
75 "keywords": [
76 "node",
77 "javascript",
78 "npm"
79 ]
80 ```
81
82 ### homepage
83
84 The URL to the project homepage.
85
86 Example:
87
88 ```json
89 "homepage": "https://github.com/npm/example#readme"
90 ```
91
92 ### bugs
93
94 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.
95
96 It should look like this:
97
98 ```json
99 {
100 "bugs": {
101 "url": "https://github.com/npm/example/issues",
102 "email": "example@npmjs.com"
103 }
104 }
105 ```
106
107 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.
108
109 If a URL is provided, it will be used by the `npm bugs` command.
110
111 ### license
112
113 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.
114
115 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:
116
117 ```json
118 {
119 "license": "BSD-3-Clause"
120 }
121 ```
122
123 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.
124
125 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:
126
127 ```json
128 {
129 "license": "(ISC OR GPL-3.0)"
130 }
131 ```
132
133 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:
134
135 ```json
136 {
137 "license": "SEE LICENSE IN <filename>"
138 }
139 ```
140
141 Then include a file named `<filename>` at the top level of the package.
142
143 Some old packages used license objects or a "licenses" property containing an array of license objects:
144
145 ```json
146 // Not valid metadata
147 {
148 "license" : {
149 "type" : "ISC",
150 "url" : "https://opensource.org/licenses/ISC"
151 }
152 }
153
154 // Not valid metadata
155 {
156 "licenses" : [
157 {
158 "type": "MIT",
159 "url": "https://www.opensource.org/licenses/mit-license.php"
160 },
161 {
162 "type": "Apache-2.0",
163 "url": "https://opensource.org/licenses/apache2.0.php"
164 }
165 ]
166 }
167 ```
168
169 Those styles are now deprecated. Instead, use SPDX expressions, like this:
170
171 ```json
172 {
173 "license": "ISC"
174 }
175 ```
176
177 ```json
178 {
179 "license": "(MIT OR Apache-2.0)"
180 }
181 ```
182
183 Finally, if you do not wish to grant others the right to use a private or unpublished package under any terms:
184
185 ```json
186 {
187 "license": "UNLICENSED"
188 }
189 ```
190
191 Consider also setting `"private": true` to prevent accidental publication.
192
193 ### people fields: author, contributors
194
195 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:
196
197 ```json
198 {
199 "name": "Barney Rubble",
200 "email": "barney@npmjs.com",
201 "url": "http://barnyrubble.npmjs.com/"
202 }
203 ```
204
205 Or you can shorten that all into a single string, and npm will parse it for you:
206
207 ```json
208 {
209 "author": "Barney Rubble <barney@npmjs.com> (http://barnyrubble.npmjs.com/)"
210 }
211 ```
212
213 Both email and url are optional either way.
214
215 npm also sets a top-level "maintainers" field with your npm user info.
216
217 ### funding
218
219 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:
220
221 ```json
222 {
223 "funding": {
224 "type": "individual",
225 "url": "http://npmjs.com/donate"
226 }
227 }
228 ```
229
230 ```json
231 {
232 "funding": {
233 "type": "patreon",
234 "url": "https://www.patreon.com/user"
235 }
236 }
237 ```
238
239 ```json
240 {
241 "funding": "http://npmjs.com/donate"
242 }
243 ```
244
245 ```json
246 {
247 "funding": [
248 {
249 "type": "individual",
250 "url": "http://npmjs.com/donate"
251 },
252 "http://npmjs.com/donate-also",
253 {
254 "type": "patreon",
255 "url": "https://www.patreon.com/user"
256 }
257 ]
258 }
259 ```
260
261 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)
262
263 ### files
264
265 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.
266
267 Some special files and directories are also included or excluded regardless of whether they exist in the `files` array (see below).
268
269 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.
270
271 Certain files are always included, regardless of settings:
272
273 - `package.json`
274 - `README`
275 - `LICENSE` / `LICENCE`
276 - The file in the "main" field
277 - The file(s) in the "bin" field
278
279 `README` & `LICENSE` can have any case and extension.
280
281 Some files are always ignored by default:
282
283 - `*.orig`
284 - `.*.swp`
285 - `.DS_Store`
286 - `._*`
287 - `.git`
288 - `.hg`
289 - `.lock-wscript`
290 - `.npmrc`
291 - `.svn`
292 - `.wafpickle-N`
293 - `CVS`
294 - `config.gypi`
295 - `node_modules`
296 - `npm-debug.log`
297 - `package-lock.json` (use [`npm-shrinkwrap.json`](/cli/v11/configuring-npm/npm-shrinkwrap-json) if you wish it to be published)
298 - `pnpm-lock.yaml`
299 - `yarn.lock`
300 - `bun.lockb`
301
302 Most of these ignored files can be included specifically if included in the `files` globs. Exceptions to this are:
303
304 - `.git`
305 - `.npmrc`
306 - `node_modules`
307 - `package-lock.json`
308 - `pnpm-lock.yaml`
309 - `yarn.lock`
310 - `bun.lockb`
311
312 These cannot be included.
313
314 ### exports
315
316 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)
317
318 ### main
319
320 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.
321
322 This should be a module relative to the root of your package folder.
323
324 For most modules, it makes the most sense to have a main script and often not much else.
325
326 If `main` is not set, it defaults to `index.js` in the package's root folder.
327
328 ### type
329
330 The `type` field defines how Node.js should interpret `.js` files in your package. This field is not used by npm.
331
332 See the [Node.js documentation on the type field](https://nodejs.org/api/packages.html#type) for more information.
333
334 ### browser
335
336 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`)
337
338 ### bin
339
340 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.)
341
342 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`.
343
344 For example, myapp could have this:
345
346 ```json
347 {
348 "bin": {
349 "myapp": "bin/cli.js"
350 }
351 }
352 ```
353
354 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.
355
356 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:
357
358 ```json
359 {
360 "name": "my-program",
361 "version": "1.2.5",
362 "bin": "path/to/program"
363 }
364 ```
365
366 would be the same as this:
367
368 ```json
369 {
370 "name": "my-program",
371 "version": "1.2.5",
372 "bin": {
373 "my-program": "path/to/program"
374 }
375 }
376 ```
377
378 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!
379
380 Note that you can also set the executable files using [directories.bin](#directoriesbin).
381
382 See [folders](/cli/v11/configuring-npm/folders#executables) for more info on executables.
383
384 ### man
385
386 Specify either a single file or an array of filenames to put in place for the `man` program to find.
387
388 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:
389
390 ```json
391 {
392 "name": "foo",
393 "version": "1.2.3",
394 "description": "A packaged foo fooer for fooing foos",
395 "main": "foo.js",
396 "man": "./man/doc.1"
397 }
398 ```
399
400 would link the `./man/doc.1` file in such that it is the target for `man foo`
401
402 If the filename doesn't start with the package name, then it's prefixed. So, this:
403
404 ```json
405 {
406 "name": "foo",
407 "version": "1.2.3",
408 "description": "A packaged foo fooer for fooing foos",
409 "main": "foo.js",
410 "man": ["./man/foo.1", "./man/bar.1"]
411 }
412 ```
413
414 will create files to do `man foo` and `man foo-bar`.
415
416 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.
417
418 ```json
419 {
420 "name": "foo",
421 "version": "1.2.3",
422 "description": "A packaged foo fooer for fooing foos",
423 "main": "foo.js",
424 "man": ["./man/foo.1", "./man/foo.2"]
425 }
426 ```
427
428 will create entries for `man foo` and `man 2 foo`
429
430 ### directories
431
432 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.
433
434 In the future, this information may be used in other creative ways.
435
436 #### directories.bin
437
438 If you specify a `bin` directory in `directories.bin`, all the files in that folder will be added.
439
440 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`.
441
442 #### directories.man
443
444 A folder that is full of man pages. Sugar to generate a "man" array by walking the folder.
445
446 ### repository
447
448 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.
449
450 Do it like this:
451
452 ```json
453 {
454 "repository": {
455 "type": "git",
456 "url": "git+https://github.com/npm/cli.git"
457 }
458 }
459 ```
460
461 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.
462
463 For GitHub, GitHub gist, Bitbucket, or GitLab repositories you can use the same shortcut syntax you use for `npm install`:
464
465 ```json
466 {
467 "repository": "npm/example",
468
469 "repository": "github:npm/example",
470
471 "repository": "gist:11081aaa281",
472
473 "repository": "bitbucket:user/repo",
474
475 "repository": "gitlab:user/repo"
476 }
477 ```
478
479 **Note on normalization:** When you publish a package, npm normalizes the `repository` field to the full object format with a `url` property. If you use a shorthand format (like `"npm/example"`), you'll see a warning during `npm publish` indicating that the field was auto-corrected. While the shorthand format currently works, it's recommended to use the full object format in your `package.json` to avoid warnings and ensure future compatibility:
480
481 ```json
482 {
483 "repository": {
484 "type": "git",
485 "url": "git+https://github.com/npm/example.git"
486 }
487 }
488 ```
489
490 You can run `npm pkg fix` to automatically convert shorthand formats to the normalized object format.
491
492 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:
493
494 ```json
495 {
496 "repository": {
497 "type": "git",
498 "url": "git+https://github.com/npm/cli.git",
499 "directory": "workspaces/libnpmpublish"
500 }
501 }
502 ```
503
504 ### scripts
505
506 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.
507
508 See [`scripts`](/cli/v11/using-npm/scripts) to find out more about writing package scripts.
509
510 ### gypfile
511
512 If you have a binding.gyp file in the root of your package and you have not defined your own `install` or `preinstall` scripts, npm will default to building your module using node-gyp.
513
514 To prevent npm from automatically building your module with node-gyp, set `gypfile` to `false`:
515
516 ```json
517 {
518 "gypfile": false
519 }
520 ```
521
522 This is useful for packages that include native addons but want to handle the build process differently, or packages that have a binding.gyp file but should not be built as a native addon.
523
524 ### config
525
526 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:
527
528 ```json
529 {
530 "name": "foo",
531 "config": {
532 "port": "8080"
533 }
534 }
535 ```
536
537 It could also have a "start" script that referenced the `npm_package_config_port` environment variable.
538
539 ### dependencies
540
541 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.
542
543 **Please do not put test harnesses or transpilers or other "development" time tools in your `dependencies` object.** See `devDependencies`, below.
544
545 See [semver](https://github.com/npm/node-semver#versions) for more details about specifying version ranges.
546
547 - `version` Must match `version` exactly
548 - `>version` Must be greater than `version`
549 - `>=version` etc
550 - `<version`
551 - `<=version`
552 - `~version` "Approximately equivalent to version" See [semver](https://github.com/npm/node-semver#versions)
553 - `^version` "Compatible with version" See [semver](https://github.com/npm/node-semver#versions)
554 - `1.2.x` 1.2.0, 1.2.1, etc., but not 1.3.0
555 - `http://...` See 'URLs as Dependencies' below
556 - `*` Matches any version
557 - `""` (just an empty string) Same as `*`
558 - `version1 - version2` Same as `>=version1 <=version2`.
559 - `range1 || range2` Passes if either range1 or range2 are satisfied.
560 - `git...` See 'Git URLs as Dependencies' below
561 - `user/repo` See 'GitHub URLs' below
562 - `tag` A specific version tagged and published as `tag` See [`npm dist-tag`](/cli/v11/commands/npm-dist-tag)
563 - `path/path/path` See [Local Paths](#local-paths) below
564 - `npm:@scope/pkg@version` Custom alias for a package See [`package-spec`](/cli/v11/using-npm/package-spec#aliases)
565
566 For example, these are all valid:
567
568 ```json
569 {
570 "dependencies": {
571 "foo": "1.0.0 - 2.9999.9999",
572 "bar": ">=1.0.2 <2.1.2",
573 "baz": ">1.0.2 <=2.3.4",
574 "boo": "2.0.1",
575 "qux": "<1.0.0 || >=2.3.1 <2.4.5 || >=2.5.2 <3.0.0",
576 "asd": "http://npmjs.com/example.tar.gz",
577 "til": "~1.2",
578 "elf": "~1.2.3",
579 "two": "2.x",
580 "thr": "3.3.x",
581 "lat": "latest",
582 "dyl": "file:../dyl",
583 "kpg": "npm:pkg@1.0.0"
584 }
585 }
586 ```
587
588 #### URLs as Dependencies
589
590 You may specify a tarball URL in place of a version range.
591
592 This tarball will be downloaded and installed locally to your package at install time.
593
594 #### Git URLs as Dependencies
595
596 Git URLs are of the form:
597
598 ```bash
599 <protocol>://[<user>[:<password>]@]<hostname>[:<port>][:][/]<path>[#<commit-ish> | #semver:<semver>]
600 ```
601
602 `<protocol>` is one of `git`, `git+ssh`, `git+http`, `git+https`, or `git+file`.
603
604 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.
605
606 Examples:
607
608 ```bash
609 git+ssh://git@github.com:npm/cli.git#v1.0.27
610 git+ssh://git@github.com:npm/cli#semver:^5.0
611 git+https://isaacs@github.com/npm/cli.git
612 git://github.com/npm/cli.git#v1.0.27
613 ```
614
615 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.
616
617 This flow will occur if your git dependency uses `workspaces`, or if any of the following scripts are present:
618
619 - `build`
620 - `prepare`
621 - `prepack`
622 - `preinstall`
623 - `install`
624 - `postinstall`
625
626 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.
627
628 #### GitHub URLs
629
630 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:
631
632 ```json
633 {
634 "name": "foo",
635 "version": "0.0.0",
636 "dependencies": {
637 "express": "expressjs/express",
638 "mocha": "mochajs/mocha#4727d357ea",
639 "module": "npm/example-github-repo#feature\/branch"
640 }
641 }
642 ```
643
644 #### Local Paths
645
646 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:
647
648 ```bash
649 ../foo/bar
650 ~/foo/bar
651 ./foo/bar
652 /foo/bar
653 ```
654
655 in which case they will be normalized to a relative path and added to your `package.json`. For example:
656
657 ```json
658 {
659 "name": "baz",
660 "dependencies": {
661 "bar": "file:../foo/bar"
662 }
663 }
664 ```
665
666 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.
667
668 _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.
669
670 ### devDependencies
671
672 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.
673
674 In this case, it's best to map these additional items in a `devDependencies` object.
675
676 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.
677
678 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.
679
680 For example:
681
682 ```json
683 {
684 "name": "@npm/ethopia-waza",
685 "description": "a delightfully fruity coffee varietal",
686 "version": "1.2.3",
687 "devDependencies": {
688 "coffee-script": "~1.6.3"
689 },
690 "scripts": {
691 "prepare": "coffee -o lib/ -c src/waza.coffee"
692 },
693 "main": "lib/waza.js"
694 }
695 ```
696
697 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.
698
699 ### peerDependencies
700
701 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.
702
703 For example:
704
705 ```json
706 {
707 "name": "@npm/tea-latte",
708 "version": "1.3.5",
709 "peerDependencies": {
710 "@npm/tea": "2.x"
711 }
712 }
713 ```
714
715 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:
716
717 ```bash
718 ├── @npm/tea-latte@1.3.5
719 └── @npm/tea@2.2.0
720 ```
721
722 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.
723
724 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.
725
726 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"`.
727
728 ### peerDependenciesMeta
729
730 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.
731
732 For example:
733
734 ```json
735 {
736 "name": "@npm/tea-latte",
737 "version": "1.3.5",
738 "peerDependencies": {
739 "@npm/tea": "2.x",
740 "@npm/soy-milk": "1.2"
741 },
742 "peerDependenciesMeta": {
743 "@npm/soy-milk": {
744 "optional": true
745 }
746 }
747 }
748 ```
749
750 ### bundleDependencies
751
752 This defines an array of package names that will be bundled when publishing the package.
753
754 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`.
755
756 For example:
757
758 If we define a package.json like this:
759
760 ```json
761 {
762 "name": "@npm/awesome-web-framework",
763 "version": "1.0.0",
764 "bundleDependencies": ["@npm/renderized", "@npm/super-streams"]
765 }
766 ```
767
768 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`.
769
770 If this is spelled `"bundledDependencies"`, then that is also honored.
771
772 Alternatively, `"bundleDependencies"` can be defined as a boolean value. A value of `true` will bundle all dependencies, a value of `false` will bundle none.
773
774 ### optionalDependencies
775
776 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.
777
778 It is still your program's responsibility to handle the lack of the dependency. For example, something like this:
779
780 ```js
781 try {
782 var foo = require("@npm/foo");
783 var fooVersion = require("@npm/foo/package.json").version;
784 } catch (er) {
785 foo = null;
786 }
787 if (notGoodFooVersion(fooVersion)) {
788 foo = null;
789 }
790
791 // .. then later in your program ..
792
793 if (foo) {
794 foo.doFooThings();
795 }
796 ```
797
798 Entries in `optionalDependencies` will override entries of the same name in `dependencies`, so it's usually best to only put in one place.
799
800 ### overrides
801
802 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.
803
804 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.
805
806 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.
807
808 To make sure the package `@npm/foo` is always installed as version `1.0.0` no matter what version your dependencies rely on:
809
810 ```json
811 {
812 "overrides": {
813 "@npm/foo": "1.0.0"
814 }
815 }
816 ```
817
818 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`:
819
820 ```json
821 {
822 "overrides": {
823 "@npm/foo": {
824 ".": "1.0.0",
825 "@npm/bar": "1.0.0"
826 }
827 }
828 }
829 ```
830
831 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`:
832
833 ```json
834 {
835 "overrides": {
836 "@npm/bar": {
837 "@npm/foo": "1.0.0"
838 }
839 }
840 }
841 ```
842
843 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`:
844
845 ```json
846 {
847 "overrides": {
848 "@npm/baz": {
849 "@npm/bar": {
850 "@npm/foo": "1.0.0"
851 }
852 }
853 }
854 }
855 ```
856
857 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`:
858
859 ```json
860 {
861 "overrides": {
862 "@npm/bar@2.0.0": {
863 "@npm/foo": "1.0.0"
864 }
865 }
866 }
867 ```
868
869 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 `$`.
870
871 ```json
872 {
873 "dependencies": {
874 "@npm/foo": "^1.0.0"
875 },
876 "overrides": {
877 // BAD, will throw an EOVERRIDE error
878 // "foo": "^2.0.0"
879 // GOOD, specs match so override is allowed
880 // "foo": "^1.0.0"
881 // BEST, the override is defined as a reference to the dependency
882 "@npm/foo": "$foo",
883 // the referenced package does not need to match the overridden one
884 "@npm/bar": "$foo"
885 }
886 }
887 ```
888
889 #### Replacing a dependency with a fork
890
891 You can replace a package with a different package or fork using several methods:
892
893 **Using the `npm:` prefix to replace with a different package name:**
894
895 ```json
896 {
897 "overrides": {
898 "package-name": "npm:@scope/forked-package@1.0.0"
899 }
900 }
901 ```
902
903 **Using a GitHub repository (supports branches, tags, or commit hashes):**
904
905 ```json
906 {
907 "overrides": {
908 "package-name": "github:username/repo#branch-name"
909 }
910 }
911 ```
912
913 **Using a local file path:**
914
915 ```json
916 {
917 "overrides": {
918 "package-name": "file:../local-fork"
919 }
920 }
921 ```
922
923 These replacement methods work for both top-level overrides and nested overrides. For example, to replace a transitive dependency with a fork:
924
925 ```json
926 {
927 "overrides": {
928 "parent-package": {
929 "vulnerable-dep": "github:username/patched-fork#v2.0.1"
930 }
931 }
932 }
933 ```
934
935 ### engines
936
937 You can specify the version of node that your stuff works on:
938
939 ```json
940 {
941 "engines": {
942 "node": ">=0.10.3 <15"
943 }
944 }
945 ```
946
947 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.
948
949 You can also use the "engines" field to specify which versions of npm are capable of properly installing your program. For example:
950
951 ```json
952 {
953 "engines": {
954 "npm": "~1.0.20"
955 }
956 }
957 ```
958
959 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.
960
961 ### os
962
963 You can specify which operating systems your module will run on:
964
965 ```json
966 {
967 "os": ["darwin", "linux"]
968 }
969 ```
970
971 You can also block instead of allowing operating systems, just prepend the blocked os with a '!':
972
973 ```json
974 {
975 "os": ["!win32"]
976 }
977 ```
978
979 The host operating system is determined by `process.platform`
980
981 It is allowed to both block and allow an item, although there isn't any good reason to do this.
982
983 ### cpu
984
985 If your code only runs on certain cpu architectures, you can specify which ones.
986
987 ```json
988 {
989 "cpu": ["x64", "ia32"]
990 }
991 ```
992
993 Like the `os` option, you can also block architectures:
994
995 ```json
996 {
997 "cpu": ["!arm", "!mips"]
998 }
999 ```
1000
1001 The host architecture is determined by `process.arch`
1002
1003 ### libc
1004
1005 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`.
1006
1007 ```json
1008 {
1009 "os": "linux",
1010 "libc": "glibc"
1011 }
1012 ```
1013
1014 ### devEngines
1015
1016 The `devEngines` field aids engineers working on a codebase to all be using the same tooling.
1017
1018 You can specify a `devEngines` property in your `package.json` which will run before `install`, `ci`, and `run` commands.
1019
1020 > 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.
1021
1022 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.
1023
1024 ```json
1025 {
1026 "devEngines": {
1027 "runtime": {
1028 "name": "node",
1029 "onFail": "error"
1030 },
1031 "packageManager": {
1032 "name": "npm",
1033 "onFail": "error"
1034 }
1035 }
1036 }
1037 ```
1038
1039 ### private
1040
1041 If you set `"private": true` in your package.json, then npm will refuse to publish it.
1042
1043 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.
1044
1045 ### publishConfig
1046
1047 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.
1048
1049 See [`config`](/cli/v11/using-npm/config) to see the list of config options that can be overridden.
1050
1051 ### workspaces
1052
1053 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.
1054
1055 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.
1056
1057 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:
1058
1059 ```json
1060 {
1061 "name": "workspace-example",
1062 "workspaces": ["./packages/*"]
1063 }
1064 ```
1065
1066 See [`workspaces`](/cli/v11/using-npm/workspaces) for more examples.
1067
1068 ### DEFAULT VALUES
1069
1070 npm will default some values based on package contents.
1071
1072 - `"scripts": {"start": "node server.js"}`
1073
1074 If there is a `server.js` file in the root of your package, then npm will default the `start` command to `node server.js`.
1075
1076 - `"scripts":{"install": "node-gyp rebuild"}`
1077
1078 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.
1079
1080 - `"contributors": [...]`
1081
1082 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.
1083
1084 ### SEE ALSO
1085
1086 - [semver](https://github.com/npm/node-semver#versions)
1087 - [workspaces](/cli/v11/using-npm/workspaces)
1088 - [npm init](/cli/v11/commands/npm-init)
1089 - [npm version](/cli/v11/commands/npm-version)
1090 - [npm config](/cli/v11/commands/npm-config)
1091 - [npm help](/cli/v11/commands/npm-help)
1092 - [npm install](/cli/v11/commands/npm-install)
1093 - [npm publish](/cli/v11/commands/npm-publish)
1094 - [npm uninstall](/cli/v11/commands/npm-uninstall)