How to Find Duplicate Files with PowerShell and Export a Report

PowerShell can narrow a duplicate-file audit by grouping files with the same size and then calculating SHA-256 hashes only for those candidates. The script below exports matching-content groups and a separate scan-error report. It never deletes or moves a file.

Set the scan folder and report paths

$RootPath = "$env:USERPROFILE\Documents"
$ReportPath = "$env:USERPROFILE\Desktop\Duplicate_Audit_Report.csv"
$ErrorPath = "$env:USERPROFILE\Desktop\Duplicate_Scan_Errors.csv"

Use size grouping before hashing

$ScanErrors = @()

$allFiles = Get-ChildItem -LiteralPath $RootPath -File -Recurse -Force `
    -ErrorAction SilentlyContinue -ErrorVariable +ScanErrors

$sizeCandidates = $allFiles |
    Group-Object -Property Length |
    Where-Object { $_.Count -gt 1 } |
    ForEach-Object { $_.Group }

$hashedFiles = foreach ($file in $sizeCandidates) {
    try {
        $hash = Get-FileHash -LiteralPath $file.FullName `
            -Algorithm SHA256 -ErrorAction Stop

        [PSCustomObject]@{
            Hash          = $hash.Hash
            Path          = $file.FullName
            SizeBytes     = $file.Length
            LastWriteTime = $file.LastWriteTime
        }
    }
    catch {
        $ScanErrors += [PSCustomObject]@{
            Path  = $file.FullName
            Stage = "Hash"
            Error = $_.Exception.Message
        }
    }
}

$report = foreach ($group in (
    $hashedFiles |
    Group-Object -Property Hash |
    Where-Object { $_.Count -gt 1 }
)) {
    $ordered = $group.Group | Sort-Object -Property Path

    for ($index = 0; $index -lt $ordered.Count; $index++) {
        [PSCustomObject]@{
            GroupHash     = $group.Name
            GroupCount    = $ordered.Count
            CandidateRank = $index + 1
            Path          = $ordered[$index].Path
            SizeMB        = [math]::Round($ordered[$index].SizeBytes / 1MB, 2)
            LastWriteTime = $ordered[$index].LastWriteTime
            ReviewNote    = "Matching SHA-256 content; review purpose and path"
        }
    }
}

if ($report) {
    $report | Export-Csv -Path $ReportPath -NoTypeInformation -Encoding UTF8
    Write-Host "Duplicate candidate report: $ReportPath"
}
else {
    Write-Host "No matching SHA-256 groups were found in the files that were scanned."
}

if ($ScanErrors) {
    $ScanErrors | Export-Csv -Path $ErrorPath -NoTypeInformation -Encoding UTF8
    Write-Warning "Some paths could not be scanned. Review: $ErrorPath"
}

Understand what the report proves

A matching SHA-256 hash is a strong indication that the scanned file contents are identical. It does not show which path is the authoritative copy, whether both copies are required, or whether an application depends on a particular location. Scan errors also mean the audit was incomplete.

Run the script

1. Save it as find-duplicates.ps1.
2. Set $RootPath to a folder you own and understand.
3. Run it in PowerShell.
4. Open both CSV files if they were created.
5. Do not proceed to cleanup until scan errors and intentional backup locations are reviewed.

Review each duplicate group

• Open files from more than one path.
• Check project, shortcut, sync, and application dependencies.
• Identify intentional archive, backup, sidecar, or distribution copies.
• Do not treat CandidateRank 1 as “the original”; it is only sorted first.
• Use the Recycle Bin or a separate holding folder before permanent deletion.

Why automatic deletion is excluded

Identical content can be intentional. A project may require a local copy, an archive may preserve a release, or software may reference a fixed path. The decision requires context the hash cannot provide.

Reduce incomplete or misleading scans

• Close applications that lock active files.
• Avoid scanning system and package directories without a specific reason.
• Exclude known backup trees if you are auditing only working folders.
• Keep the error CSV with the duplicate report.
• Repeat the scan after moving candidates to confirm no unexpected group remains.

Completion checklist

• The root path was intentional.
• Any scan or hash errors were reviewed.
• Each planned deletion has another verified copy.
• Dependent projects and applications were checked.
• Files were held temporarily before permanent removal.
• A post-cleanup scan and backup verification were completed.

Official Microsoft reference

• Get-FileHash