About PSModulePath

The $env:PSModulePath environment variable contains a list of folder locations that are searched to find modules and resources.

By default, the effective locations assigned to $env:PSModulePath are:

  • System-wide locations: These folders contain modules that ship with PowerShell. These modules are store in the $PSHOME\Modules folder. This is also the location where the Windows management modules are installed.

  • User-installed modules: These are modules installed by the user. Install-Module has a Scope parameter that allows you to specify whether the module is installed for the current user or for all users. For more information, see Install-Module.

    • On Windows, the location of the user-specific CurrentUser scope is the $HOME\Documents\PowerShell\Modules folder. The location of the AllUsers scope is $env:ProgramFiles\PowerShell\Modules.
    • On non-Windows systems, the location of the user-specific CurrentUser scope is the $HOME/.local/share/powershell/Modules folder. The location of the AllUsers scope is /usr/local/share/powershell/Modules.

In addition, setup programs that install modules in other directories, such as the Program Files directory, can append their locations to the value of $env:PSModulePath.

Note

On Windows, the user-specific location is the PowerShell\Modules folder located in the Documents folder in your user profile. The specific path of that location varies by version of Windows and whether or not you are using folder redirection. Microsoft OneDrive can also change the location of your Documents folder. You can verify the location of your Documents folder using the following command: [Environment]::GetFolderPath('MyDocuments').

Modifying PSModulePath

To change the default module directories for the current session, use the following command format to change the value of the PSModulePath environment variable.

For example, to add the C:\Program Files\Fabrikam\Modules directory to the value of the PSModulePath environment variable, type:

$Env:PSModulePath = $Env:PSModulePath+";C:\Program Files\Fabrikam\Modules"

The semi-colon (;) in the command separates the new path from the path that precedes it in the list. On non-Windows platforms, the colon (:) separates the path locations in the environment variable.

To change the value of PSModulePath in every session, add the previous command to your PowerShell profile or use the SetEnvironmentVariable method of the Environment class.

The following command uses the GetEnvironmentVariable method to get the machine setting of PSModulePath and the SetEnvironmentVariable method to add the C:\Program Files\Fabrikam\Modules path to the value.

$path = [Environment]::GetEnvironmentVariable('PSModulePath', 'Machine')
$newpath = $path + ';C:\Program Files\Fabrikam\Modules'
[Environment]::SetEnvironmentVariable('PSModulePath', $newpath, 'Machine')

To add a path to the user setting, change the target value to User.

$path = [Environment]::GetEnvironmentVariable('PSModulePath', 'User')
$newpath = $path + ';C:\Program Files\Fabrikam\Modules'
[Environment]::SetEnvironmentVariable('PSModulePath', $newpath, 'User')

For more information about the methods of the System.Environment class, see Environment Methods.

PowerShell PSModulePath construction

The value of $env:PSModulePath is constructed each time PowerShell starts. The value varies by version of PowerShell and how it is launched.

Windows PowerShell startup

Windows PowerShell uses the following logic to construct the PSModulePath at startup:

  • If PSModulePath doesn't exist, combine CurrentUser, AllUsers, and the $PSHOME modules paths
  • If PSModulePath does exist:
    • If PSModulePath contains $PSHOME modules path:
      • AllUsers modules path is inserted before $PSHOME modules path
    • else:
      • Just use PSModulePath as defined since the user deliberately removed the $PSHOME location

The CurrentUser module path is prefixed only if User scope $env:PSModulePath doesn't exist. Otherwise, the User scope $env:PSModulePath is used as defined.

PowerShell Core 6 startup

PowerShell Core 6 doesn't use contents of $env:PSModulePath if it detects it was started from PowerShell. It overwrites it with:

  • CurrentUser modules path + AllUsers modules path + $PSHOME modules path + Windows PowerShell $PSHOME modules path.

PowerShell 7 startup

In Windows, for most environment variables, if the User-scoped variable exists, a new process uses that value only even if a Machine-scoped variable of the same name exists.

In PowerShell 7, PSModulePath is treated similar to how the Path environment variable is treated on Windows. On Windows, Path is treated differently from other environment variables. When a process is started, Windows combines the User-scoped Path with the Machine-scoped Path.

  • Retrieve the User-scoped PSModulePath
  • Compare to process inherited PSModulePath environment variable
    • If the same:
      • Append the AllUsers PSModulePath to the end following the semantics of the Path environment variable
      • The Windows System32 path comes from the machine defined PSModulePath so does not need to be added explicitly
    • If different, treat as though user explicitly modified it and don't append AllUsers PSModulePath
  • Prefix with PS7 User, System, and $PSHOME paths in that order
    • If powershell.config.json contains a user scoped PSModulePath, use that instead of the default for the user
    • If powershell.config.json contains a system scoped PSModulePath, use that instead of the default for the system

Unix systems don't have a separation of User and System environment variables. PSModulePath is inherited and the PS7-specific paths are prefixed if not already defined.

Starting Windows PowerShell from PowerShell 7

For this discussion, Windows PowerShell means both powershell.exe and powershell_ise.exe.

The value of $env:PSModulePath is copied to WinPSModulePath with the following modifications:

  • Remove PS7 the User module path
  • Remove PS7 the System module path
  • Remove PS7 the $PSHOME module path

The PS7 paths are removed so that PS7 modules don't get loaded in Windows PowerShell. The WinPSModulePath value is used when starting Windows PowerShell.

Starting PowerShell 7 from Windows PowerShell

The PowerShell 7 startup continues as-is with the addition of inheriting paths that Windows PowerShell added. Since the PS7-specific paths are prefixed, there is no functional issue.

Starting PowerShell 6 from PowerShell 7

PowerShell Core 6 overwrites $env:PSModulePath. No changes are made.

Starting PowerShell 7 from PowerShell 6

The PowerShell 7 startup continues as-is with the addition of inheriting paths that PowerShell Core 6 added. Since the PS7-specific paths are prefixed, there is no functional issue.

See also