Setup-FnmWindows.ps1

A PowerShell script to install and configure Fast Node Manager (fnm) on Windows.

This script is intended to make it easy to set up fnm on a user’s machine. It handles detection of existing Node.js managers, installation via winget, and configuration of shell startup files so that fnm works automatically.

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Features

• Detects and warns if nvm-windows is installed (recommends uninstalling to avoid conflicts).
• Detects and warns if a system Node.js install is present (if fnm isn’t installed yet).
• Installs fnm via winget if not already installed.
• Configures fnm env for:
  • PowerShell (Windows PowerShell 5.x and PowerShell 7+ profiles, OneDrive-aware).
  • Command Prompt (via profile.cmd + registry AutoRun).
  • Git Bash (~/.bashrc).
• Adds the flag --version-file-strategy=recursive to fnm env for project-based version resolution.
• Reloads the current PowerShell profile so fnm is available immediately in the same session.
• Optionally installs and sets a default Node.js version (e.g. 22, lts, or latest).
• Supports DryRun and DetectOnly modes.

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Parameters

-Shells

Which shells to configure. Accepts one or more of:

• pwsh – PowerShell (Windows PowerShell 5.x and PowerShell 7+)
• cmd – Command Prompt
• gitbash – Git Bash

Default: pwsh,cmd,gitbash

-Shells pwsh,cmd

-NodeVersion

Install and set a default Node.js version using fnm.

-NodeVersion 22
-NodeVersion lts

-DetectOnly

Only check for nvm, fnm, and Node.js. Print findings and exit.
No installations, file edits, or registry changes are made.

-DetectOnly

-DryRun

Preview what changes would be made (file writes, registry edits, installs).
No actual modifications are made.

-DryRun

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Usage Examples

Detect environment only

.\Setup-FnmWindows.ps1 -DetectOnly

Preview changes for PowerShell and cmd

.\Setup-FnmWindows.ps1 -Shells pwsh,cmd -DryRun

Install fnm, configure all shells, and install Node.js 22

.\Setup-FnmWindows.ps1 -Shells pwsh,cmd,gitbash -NodeVersion 22

Configure only PowerShell (no Node install)

.\Setup-FnmWindows.ps1 -Shells pwsh

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After Running

• For PowerShell, the script reloads your profile, so you can run fnm --version immediately.
• For cmd and Git Bash, you must open a new terminal window after running the script.

Validate installation with:

fnm --version
node --version

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Notes

• If nvm-windows is detected, you should uninstall it before using fnm (they conflict in how they manage Node.js).
• If a system Node.js is detected and fnm is not installed yet, the script recommends uninstalling system Node to avoid conflicts.
• Requires winget (App Installer) to install fnm. If missing, install App Installer from the Microsoft Store.
• Requires the ability to executes scripts on your local machine, Set-Execution Policy.

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License

MIT – use at your own risk. Contributions welcome!