This PowerShell script finds file extensions that are not shown even when Windows is set to show extensions, then outputs the results to a csv file spreadsheet

GetSuperHiddenExtensions.ps1

# This script will search through the Windows Registry to find file extensions that are not shown even when the "Hide extensions for known file types" option is disabled.
# It does this by looking for file types with the NeverShowExt property set, as well as any CLSID references associated with the file types.
# Author: ThioJoe
# Updated: 9/4/2024 (First Version)
#
# How to Use:
# 1. Open PowerShell and navigate to the path containing this script using the 'cd' command.
# 2. Run the following command to allow running scripts for the current session:
#        Set-ExecutionPolicy -ExecutionPolicy unrestricted -Scope Process
# 3. Without closing the PowerShell window, run the script by typing the name of the script file starting with  .\  for example:
#        .\GetSuperHiddenExtensions.ps1


# Arrays to store file types and CLSIDs with NeverShowExt property
$neverShowExtTypes = @()
$neverShowExtCLSIDs = @()

# Function to get the file extension for a given file type
function Get-FileExtension($fileType) {
    $extensions = Get-ChildItem -Path "Registry::HKEY_CLASSES_ROOT" |
        Where-Object { $_.GetValue("") -eq $fileType } |
        Select-Object -ExpandProperty PSChildName
    return $extensions
}

# Function to search for NeverShowExt in CLSID
function Search-CLSIDForNeverShowExt {
    Write-Host "Searching through HKEY_CLASSES_ROOT\CLSID for NeverShowExt..." -ForegroundColor Green
    $clsidPath = "Registry::HKEY_CLASSES_ROOT\CLSID"

    Get-ChildItem -Path $clsidPath | ForEach-Object {
        $key = $_
        $properties = $key.GetValueNames()
        if ($properties -contains "NeverShowExt") {
            $clsid = $key.PSChildName
            $friendlyName = $key.GetValue("")  # Get the (Default) value
            Write-Host "Found NeverShowExt property for CLSID $clsid" -ForegroundColor Yellow
            $script:neverShowExtCLSIDs += [PSCustomObject]@{
                CLSID = $clsid
                FriendlyName = $friendlyName
            }
        }
    }
}

# Function to search main HKEY_CLASSES_ROOT
function Search-HKCRForNeverShowExt {
    Write-Host "Searching through HKEY_CLASSES_ROOT for NeverShowExt and CLSID references..." -ForegroundColor Green

    Get-ChildItem -Path "Registry::HKEY_CLASSES_ROOT" | ForEach-Object {
        $key = $_
        $properties = $key.GetValueNames()
        if ($properties -contains "NeverShowExt") {
            $fileType = $key.PSChildName
            $friendlyName = $key.GetValue("")  # Get the (Default) value
            Write-Host "Found NeverShowExt property for $fileType" -ForegroundColor Yellow
            $script:neverShowExtTypes += [PSCustomObject]@{
                FileType = $fileType
                FriendlyName = $friendlyName
                Extensions = (Get-FileExtension $fileType) -join ', '
                CLSID = $null
            }
        }

        # Check for CLSID references
        $defaultValue = $null
        $defaultValue = $key.GetValue("")
        if ($defaultValue) {
            # The default value will look like:  CLSID\{9E56BE61-C50F-11CF-9A2C-00A0C90A90CE}  , so need to just get after CLSID\
            $clsidValue = $defaultValue -replace '.*CLSID\\', ''
            $match = $null
            if ($clsidValue -and ($match = $script:neverShowExtCLSIDs | Where-Object { $_.CLSID -eq $clsidValue })) {
                $friendlyName = $match.FriendlyName

                Write-Host "Found CLSID reference for $($key.PSChildName)" -ForegroundColor Magenta
                $extensions = $null
                $extensions = (Get-FileExtension $key.PSChildName) -join ', '
                if (-not $extensions -and $key.PSChildName.StartsWith('.')) {
                    $extensions = $key.PSChildName
                }

                $script:neverShowExtTypes += [PSCustomObject]@{
                    FileType = $key.PSChildName
                    FriendlyName = $match.FriendlyName
                    Extensions   = $extensions
                    CLSID = $clsidValue
                }
            }
        }
    }
}

# Main execution
Search-CLSIDForNeverShowExt
Search-HKCRForNeverShowExt

Write-Host "Registry search completed. Preparing output..." -ForegroundColor Green

# Prepare CSV output
$outputPath = "NeverShowExtTypes.csv"
$neverShowExtTypes | Export-Csv -Path $outputPath -NoTypeInformation

Write-Host "Script completed. Results have been saved to $outputPath" -ForegroundColor Green
Write-Host "Found $($neverShowExtTypes.Count) file types with NeverShowExt property or associated CLSID." -ForegroundColor Green

# Display a preview of the CSV content
Write-Host "`nPreview of CSV content:" -ForegroundColor Cyan
Import-Csv $outputPath | Select-Object -First 5 | Format-Table -AutoSize

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