1FOLDERS(5) FOLDERS(5)
2
6 folders - Folder Structures Used by npm
7 Description
9 npm puts various things on your computer. That's its job.
10 This document will tell you what it puts where.
12 tl;dr
14 • Local install (default): puts stuff in ./node_modules of the current
15 package root.
16 • Global install (with -g): puts stuff in /usr/local or wherever node
18 is installed.
19 • Install it locally if you're going to require() it.
21 • Install it globally if you're going to run it on the command line.
23 • If you need both, then install it in both places, or use npm link.
25 prefix Configuration
28 The prefix config defaults to the location where node is installed. On
29 most systems, this is /usr/local. On Windows, it's %AppData%\npm. On
30 Unix systems, it's one level up, since node is typically installed at
31 {prefix}/bin/node rather than {prefix}/node.exe.
32 When the global flag is set, npm installs things into this prefix.
34 When it is not set, it uses the root of the current package, or the
35 current working directory if not in a package already.
36 Node Modules
38 Packages are dropped into the node_modules folder under the prefix.
39 When installing locally, this means that you can require("packagename")
40 to load its main module, or require("packagename/lib/path/to/sub/mod‐
41 ule") to load other modules.
42 Global installs on Unix systems go to {prefix}/lib/node_modules.
44 Global installs on Windows go to {prefix}/node_modules (that is, no lib
45 folder.)
46 Scoped packages are installed the same way, except they are grouped to‐
48 gether in a sub-folder of the relevant node_modules folder with the
49 name of that scope prefix by the @ symbol, e.g. npm install @my‐
50 org/package would place the package in {prefix}/node_modules/@my‐
51 org/package. See npm help scope for more details.
52 If you wish to require() a package, then install it locally.
54 Executables
56 When in global mode, executables are linked into {prefix}/bin on Unix,
57 or directly into {prefix} on Windows. Ensure that path is in your ter‐
58 minal's PATH environment to run them.
59 When in local mode, executables are linked into ./node_modules/.bin so
61 that they can be made available to scripts run through npm. (For exam‐
62 ple, so that a test runner will be in the path when you run npm test.)
63 Man Pages
65 When in global mode, man pages are linked into {prefix}/share/man.
66 When in local mode, man pages are not installed.
68 Man pages are not installed on Windows systems.
70 Cache
72 See npm help cache. Cache files are stored in ~/.npm on Posix, or %Ap‐
73 pData%/npm-cache on Windows.
74 This is controlled by the cache configuration param.
76 Temp Files
78 Temporary files are stored by default in the folder specified by the
79 tmp config, which defaults to the TMPDIR, TMP, or TEMP environment
80 variables, or /tmp on Unix and c:\windows\temp on Windows.
81 Temp files are given a unique folder under this root for each run of
83 the program, and are deleted upon successful exit.
84 More Information
86 When installing locally, npm first tries to find an appropriate prefix
87 folder. This is so that npm install foo@1.2.3 will install to the sen‐
88 sible root of your package, even if you happen to have cded into some
89 other folder.
90 Starting at the $PWD, npm will walk up the folder tree checking for a
92 folder that contains either a package.json file, or a node_modules
93 folder. If such a thing is found, then that is treated as the effec‐
94 tive "current directory" for the purpose of running npm commands.
95 (This behavior is inspired by and similar to git's .git-folder seeking
96 logic when running git commands in a working dir.)
97 If no package root is found, then the current folder is used.
99 When you run npm install foo@1.2.3, then the package is loaded into the
101 cache, and then unpacked into ./node_modules/foo. Then, any of foo's
102 dependencies are similarly unpacked into ./node_modules/foo/node_mod‐
103 ules/....
104 Any bin files are symlinked to ./node_modules/.bin/, so that they may
106 be found by npm scripts when necessary.
107 Global Installation
109 If the global configuration is set to true, then npm will install pack‐
110 ages "globally".
111 For global installation, packages are installed roughly the same way,
113 but using the folders described above.
114 Cycles, Conflicts, and Folder Parsimony
116 Cycles are handled using the property of node's module system that it
117 walks up the directories looking for node_modules folders. So, at ev‐
118 ery stage, if a package is already installed in an ancestor node_mod‐
119 ules folder, then it is not installed at the current location.
120 Consider the case above, where foo -> bar -> baz. Imagine if, in addi‐
122 tion to that, baz depended on bar, so you'd have: foo -> bar -> baz ->
123 bar -> baz .... However, since the folder structure is: foo/node_mod‐
124 ules/bar/node_modules/baz, there's no need to put another copy of bar
125 into .../baz/node_modules, since when it calls require("bar"), it will
126 get the copy that is installed in foo/node_modules/bar.
127 This shortcut is only used if the exact same version would be installed
129 in multiple nested node_modules folders. It is still possible to have
130 a/node_modules/b/node_modules/a if the two "a" packages are different
131 versions. However, without repeating the exact same package multiple
132 times, an infinite regress will always be prevented.
133 Another optimization can be made by installing dependencies at the
135 highest level possible, below the localized "target" folder.
136 Example
138 Consider this dependency graph:
139 foo
141 +-- blerg@1.2.5
142 +-- bar@1.2.3
143 | +-- blerg@1.x (latest=1.3.7)
144 | +-- baz@2.x
145 | | `-- quux@3.x
146 | | `-- bar@1.2.3 (cycle)
147 | `-- asdf@*
148 `-- baz@1.2.3
149 `-- quux@3.x
150 `-- bar
151 In this case, we might expect a folder structure like this:
153 foo
155 +-- node_modules
156 +-- blerg (1.2.5) <---[A]
157 +-- bar (1.2.3) <---[B]
158 | `-- node_modules
159 | +-- baz (2.0.2) <---[C]
160 | | `-- node_modules
161 | | `-- quux (3.2.0)
162 | `-- asdf (2.3.4)
163 `-- baz (1.2.3) <---[D]
164 `-- node_modules
165 `-- quux (3.2.0) <---[E]
166 Since foo depends directly on bar@1.2.3 and baz@1.2.3, those are in‐
168 stalled in foo's node_modules folder.
169 Even though the latest copy of blerg is 1.3.7, foo has a specific de‐
171 pendency on version 1.2.5. So, that gets installed at [A]. Since the
172 parent installation of blerg satisfies bar's dependency on blerg@1.x,
173 it does not install another copy under [B].
174 Bar [B] also has dependencies on baz and asdf, so those are installed
176 in bar's node_modules folder. Because it depends on baz@2.x, it cannot
177 re-use the baz@1.2.3 installed in the parent node_modules folder [D],
178 and must install its own copy [C].
179 Underneath bar, the baz -> quux -> bar dependency creates a cycle.
181 However, because bar is already in quux's ancestry [B], it does not un‐
182 pack another copy of bar into that folder.
183 Underneath foo -> baz [D], quux's [E] folder tree is empty, because its
185 dependency on bar is satisfied by the parent folder copy installed at
186 [B].
187 For a graphical breakdown of what is installed where, use npm ls.
189 Publishing
191 Upon publishing, npm will look in the node_modules folder. If any of
192 the items there are not in the bundledDependencies array, then they
193 will not be included in the package tarball.
194 This allows a package maintainer to install all of their dependencies
196 (and dev dependencies) locally, but only re-publish those items that
197 cannot be found elsewhere. See npm help package.json for more informa‐
198 tion.
199 See also
201 • npm help package.json
202 • npm help install
204 • npm help pack
206 • npm help cache
208 • npm help config
210 • npm help npmrc
212 • npm help config
214 • npm help publish
216 January 2022 FOLDERS(5)