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Get duplicate Intune devices by serialnumber

Sometimes it happens that there are several devices with the same serial number in Intune. This can happen for example when switching from AD/SCCM built clients to Intune only clients.

This script helps to find the duplicate entries. At the end a CSV is output, which can be cleaned manually or with another script.

This script fetches all Intune Devices and then goes through and, if there are multiple devices per serial number, stores the device information in an array.

PowerShell Script

Add your own access token and app name in the corresponding PowerShell variables.

$Global:MicrosoftEntraIDAccessToken = ""

# Get All Intune Windows Devices
$uri = "`$filter=startswith(operatingSystem,'windows')"
$Results = Invoke-RestMethod -Method GET -Uri $uri -ContentType "application/json" -Headers @{Authorization = "Bearer $($Global:MicrosoftEntraIDAccessToken)"; ConsistencyLevel = "eventual" }
$IntuneDevices = $results.value
if ($results."@odata.nextLink" -ne $null) {
    $NextPageUri = $results."@odata.nextLink"
    While ($NextPageUri -ne $null) {
        $NextPageRequest = (Invoke-RestMethod -Headers @{Authorization = "Bearer $($Global:MicrosoftEntraIDAccessToken)" } -Uri $NextPageURI -Method Get)
        $NxtPageData = $NextPageRequest.Value
        $NextPageUri = $NextPageRequest."@odata.nextLink"
        $IntuneDevices += $NxtPageData

# Get all devices by SerialNumber
$DuplicateDevices = @()
foreach($IntuneDevice in $IntuneDevices){
    $Results = Invoke-RestMethod -Method GET -Uri "`$filter=contains(serialNumber,'$($IntuneDevice.serialnumber)')" -ContentType "application/json" -Headers @{Authorization = "Bearer $($Global:MicrosoftEntraIDAccessToken)"}
    if($Results.value.count -gt 1){
        if($DuplicateDevices.serialnumber -contains $Results.value.serialnumber){
            $DuplicateDevices += $Results.value
            $DuplicateDevices += $Results.value

# Output all duplicate Devices
$DuplicateDevices | Export-CSV "<yourpathtocsv>" -NoTypeInformation