PACKAGE-LOCK.JSON

NAME

package-lock.json

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.

•

Facilitate greater visibility of tree changes through readable source

control diffs.

•

Optimize the installation process by allowing npm to skip repeated

metadata resolutions for previously-installed packages.

•

As of npm v7, lockfiles include enough information to gain a complete

picture of the package tree, reducing the need to read package.json
files, and allowing for significant performance improvements.

package-lock.json vs npm-shrinkwrap.json

Both of these files have the same format, and perform similar functions in
the root of a project.

The difference is that package-lock.json cannot be published, and it will
be ignored if found in any place other than the root project.

In contrast, npm-shrinkwrap.json allows
publication, and defines the dependency tree from the point encountered.
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 project, npm-shrinkwrap.json will take precedence and
package-lock.json will be ignored.

Hidden Lockfiles

In order to avoid processing the node_modules folder repeatedly, npm as
of v7 uses a "hidden" lockfile present in
node_modules/.package-lock.json. This contains information about the
tree, and is used in lieu of reading the entire node_modules hierarchy
provided that the following conditions are met:

	•		All package folders it references exist in the node_modules hierarchy.
	•		No package folders exist in the node_modules hierarchy that are not

listed in the lockfile.

•

The modified time of the file is at least as recent as all of the package

folders it references.

That is, the hidden lockfile will only be relevant if it was created as
part of the most recent update to the package tree. If another CLI mutates
the tree in any way, this will be detected, and the hidden lockfile will be
ignored.

Note that it is possible to manually change the contents of a package
in such a way that the modified time of the package folder is unaffected.
For example, if you add a file to node_modules/foo/lib/bar.js, then the
modified time on node_modules/foo will not reflect this change. If you
are manually editing files in node_modules, it is generally best to
delete the file at node_modules/.package-lock.json.

As the hidden lockfile is ignored by older npm versions, it does not
contain the backwards compatibility affordances present in "normal"
lockfiles. That is, it is lockfileVersion: 3, rather than
lockfileVersion: 2.

Handling Old Lockfiles

When npm detects a lockfile from npm v6 or before during the package
installation process, it is automatically updated to fetch missing
information from either the node_modules tree or (in the case of empty
node_modules trees or very old lockfile formats) the npm registry.

File Format

name

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

version

The version of the package this is a package-lock for. This will 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.

Note that the file format changed significantly in npm v7 to track
information that would have otherwise required looking in node_modules or
the npm registry. Lockfiles generated by npm v7 will contain
lockfileVersion: 2.

•

No version provided: an "ancient" shrinkwrap file from a version of npm

prior to npm v5.

	•		1: The lockfile version used by npm v5 and v6.
	•		2: The lockfile version used by npm v7, which is backwards compatible

to v1 lockfiles.

•

3: The lockfile version used by npm v7, without backwards

compatibility affordances. This is used for the hidden lockfile at
node_modules/.package-lock.json, and will likely be used in a future
version of npm, once support for npm v6 is no longer relevant.

npm will always attempt to get whatever data it can out of a lockfile, even
if it is not a version that it was designed to support.

packages

This is an object that maps package locations to an object containing the
information about that package.

The root project is typically listed with a key of "", and all other
packages are listed with their relative paths from the root project folder.

Package descriptors have the following fields:

	•		version: The version found in package.json
	•		resolved: The place where the package was actually resolved from. In

the case of packages fetched from the registry, this will be a url to a
tarball. In the case of git dependencies, this will be the full git url
with commit sha. In the case of link dependencies, this will be the
location of the link target. registry.npmjs.org is a magic value meaning
"the currently configured registry".

•

integrity: A sha512 or sha1 Standard Subresource

Integrity
string for the artifact that was unpacked in this location.

•

link: A flag to indicate that this is a symbolic link. If this is

present, no other fields are specified, since the link target will also
be included in the lockfile.

•

dev, optional, devOptional: If the package is strictly part of the

devDependencies tree, then dev will be true. If it is strictly part
of the optionalDependencies tree, then optional will be set. If it
is both a dev dependency and an optional dependency of a non-dev
dependency, then devOptional will be set. (An optional dependency of
a dev dependency will have both dev and optional set.)

	•		inBundle: A flag to indicate that the package is a bundled dependency.
	•		hasInstallScript: A flag to indicate that the package has a preinstall,

install, or postinstall script.

•

hasShrinkwrap: A flag to indicate that the package has an

npm-shrinkwrap.json file.

•

bin, license, engines, dependencies, optionalDependencies: fields from

package.json

dependencies

Legacy data for supporting versions of npm that use lockfileVersion: 1.
This is a mapping of package names to dependency objects. Because the
object structure is strictly hierarchical, symbolic link dependencies are
somewhat challenging to represent in some cases.

npm v7 ignores this section entirely if a packages section is present,
but does keep it up to date in order to support switching between npm v6
and npm v7.

Dependency objects have the following fields:

•

version: a specifier that varies depending on the nature of the package,

and is 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: A sha512 or sha1 Standard Subresource

Integrity
string for the artifact that was unpacked in this location. For git
dependencies, this is the commit sha.

•

resolved: 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. registry.npmjs.org is a magic
value meaning "the currently configured registry".

•

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.

•

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

	•		npm shrinkwrap
	•		npm-shrinkwrap.json
	•		package.json
	•		npm install