Frequently Asked Questions

Why does my `node_modules` folder use disk space if packages are stored in a global store?

pnpm creates hard links from the global store to project's node_modules folders. Hard links point to the same place on the disk where the original files are. So, for example, if you have foo in your project as a dependency and it occupies 1MB of space, then it will look like it occupies 1MB of space in the project's node_modules folder and the same amount of space in the global store. However, that 1MB is the same space on the disk addressed from two different locations. So in total foo occupies 1MB, not 2MB.

For more on this subject:

Does it work on Windows? It is harder to create symlinks on Windows

Using symlinks on Windows is problematic indeed. That is why pnpm uses junctions instead of symlinks on Windows OS.

Does it work on Windows? Nested `node_modules` approach is basically incompatible with Windows

Early versions of npm had issues because of nesting all node_modules (see Node's nested node_modules approach is basically incompatible with Windows). However, pnpm does not create deep folders, it stores all packages flatly and uses symlinks to create the dependency tree structure.

What about circular symlinks?

Although pnpm uses symlinks to put dependencies into node_modules folders, circular symlinks are avoided because parent packages are placed into the same node_modules folder in which their dependencies are. So foo's dependencies are not in foo/node_modules but foo is in node_modules/foo, together with its own dependencies.

Why have hard links at all? Why not symlink directly to the global store?

One package can have different sets of dependencies on one machine.

In project A foo@1.0.0 can have dependency resolved to bar@1.0.0 but in project B the same dependency of foo might resolve to bar@1.1.0. So pnpm hard links foo@1.0.0 to every project where it is used, in order to create different sets of dependencies for it.

Direct symlinking to the global store would work with Node's --preserve-symlinks flag. But --preserve-symlinks comes with a bunch of different issues, so we decided to stick with hard links. For more details about why this decision was made, see: https://github.com/nodejs/node-eps/issues/46.

Does pnpm work across multiple hard drives or filesystems?

The package store should be on the same disk as installations. Otherwise packages will be copied, not linked. This is due to a OS limitation in hard-linking. See Issue #712 for more details.

pnpm functions differently based on the 2 cases below:

Store path is specified

If the store path is specified via the store config, then copying occurs between the store and any projects that are on a different disk.

If you run pnpm install on disk D:, then the pnpm store must be on disk D:. If the pnpm store is located on disk C:, then all required packages will be directly copied to the project location. This severely reduces the benefits of pnpm.

Store path is NOT specified

If the store path is not set, then multiple stores are created (one per each drive or filesystem).

If installation is run on disk D:, the store will be created in D:\.pnpm-store. If later the installation is run on disk C:, an independent store will be created in C:\.pnpm-store. The projects would still maintain the benefits of pnpm, but each drive may have redundant packages.

What does `pnpm store prune` do? Is it harmful?

The command pnpm store prune removes unreferenced packages.

Unreferenced packages are packages that are not used by any projects on the system. Packages can become unreferenced after most installation operations.

For example: during pnpm install, package foo@1.0.0 is updated to foo@1.0.1. pnpm will keep foo@1.0.0 in the store, as it does not automatically remove packages. If package foo@1.0.0 is not used by any other project on the system, it becomes unreferenced. Running pnpm store prune would remove foo@1.0.0 from the store.

Running pnpm store prune is not harmful and has no side effects on your projects. If future installations require removed packages, pnpm will download them again.

It is best practice to run pnpm store prune occasionally to clean up the store, but not too frequently. Sometimes, unreferenced packages become required again. This could occur when switching branches and installing older dependencies. Then pnpm would need to re-download all removed packages, briefly slowing down the installation process.

What does `pnpm` stand for?

pnpm stands for performant npm. Rico Sta. Cruz came up with the name.

`pnpm` does not work with <YOUR-PROJECT-HERE>?

In most cases it means that one of the dependencies require packages not declared in package.json. It is a common mistake caused by flat node_modules. If this happens, this is an error in the dependency and the dependency should be fixed. That might take time though, so pnpm supports workarounds to make the buggy packages work.

Solution 1

In the following example, a dependency does not have the iterall module in its own list of deps.

The easiest solution to resolve missing dependencies of the buggy packages is to add iterall as a dependency to our project's package.json.

You can do so, by installing it via:

pnpm i iterall

It will be automatically added to your project's package.json.

  "dependencies": {
    ...
    "iterall": "^1.2.2",
    ...
  }

Solution 2

One of the solutions is to use hooks for adding the missing dependencies to the package's package.json.

An example was Webpack Dashboard which wasn't working with pnpm. It has since been resolved such that it works with pnpm now.

It used to throw an error:

Error: Cannot find module 'babel-traverse'
  at /node_modules/.registry.npmjs.org/inspectpack/2.2.3/node_modules/inspectpack/lib/actions/parse

The problem was that babel-traverse was used in inspectpack library which was used by webpack-dashboard. But babel-traverse wasn't specified in inspectpack's package.json. It still worked with npm and yarn because they create flat node_modules.

Solution was to create a pnpmfile.js with the following contents:

module.exports = {
  hooks: {
    readPackage (pkg) {
      switch (pkg.name) {
        case 'inspectpack':
          pkg.dependencies['babel-traverse'] = '^6.26.0'
          break
      }
      return pkg
    }
  }
}

After creating pnpmfile.js, delete pnpm-lock.yaml only. No need to delete node_modules. Then install the dependencies & it should be working.

Solution 3

In case there are too many issues, you can use the shamefully-hoist config. This creates a flat node_modules structure similar to the one created by npm or yarn.

To use it, try pnpm install --shamefully-hoist.

Why does my node_modules folder use disk space if packages are stored in a global store?