SharePoint Online: Copy List Items between Site Collections using PowerShell

Requirement: Copy List Items between Site Collections in SharePoint Online using PowerShell

PowerShell to Copy List Items between SharePoint Online Site Collections
Just set parameters accordingly and run the script. Make sure your target list is already created with the same structure (either by creating a new list from existing list or save the list as a template and create a new list instance, so that the internal names are intact!).

#Function to copy attachments between list items
Function Copy-SPOAttachments()
{
    param
    (
        [Parameter(Mandatory=$true)] [Microsoft.SharePoint.Client.ListItem] $SourceItem,
        [Parameter(Mandatory=$true)] [Microsoft.SharePoint.Client.ListItem] $DestinationItem
    )
    Try {
        #Get All Attachments from Source list items
        $Attachments = Get-PnPProperty -ClientObject $SourceItem -Property "AttachmentFiles"
        $Attachments | ForEach-Object {
            #Download the Attachment to Temp
            $File  = Get-PnPFile -Connection $SourceConn -Url $_.ServerRelativeUrl -FileName $_.FileName -Path $Env:TEMP -AsFile -force
            #Add Attachment to Destination List Item
            $FileStream = New-Object IO.FileStream(($Env:TEMP+"\"+$_.FileName),[System.IO.FileMode]::Open)  
            $AttachmentInfo = New-Object -TypeName Microsoft.SharePoint.Client.AttachmentCreationInformation
            $AttachmentInfo.FileName = $_.FileName
            $AttachmentInfo.ContentStream = $FileStream
            $AttachFile = $DestinationItem.AttachmentFiles.Add($AttachmentInfo)
            Invoke-PnPQuery -Connection $DestinationConn
      
            #Delete the Temporary File
            Remove-Item -Path $Env:TEMP\$($_.FileName) -Force
        }
    }
    Catch {
        write-host -f Red "Error Copying Attachments:" $_.Exception.Message
    }
}
 
#Function to copy list items from one list to another
Function Copy-SPOListItems()
{
    param
    (
        [Parameter(Mandatory=$true)] [Microsoft.SharePoint.Client.List] $SourceList,
        [Parameter(Mandatory=$true)] [Microsoft.SharePoint.Client.List] $DestinationList
    )
    Try {
        #Get All Items from the Source List in batches 
        Write-Progress -Activity "Reading Source..." -Status "Getting Items from Source List. Please wait..."
        $SourceListItems = Get-PnPListItem -List $SourceList -PageSize 500 -Connection $SourceConn
        $SourceListItemsCount= $SourceListItems.count
        Write-host "Total Number of Items Found:"$SourceListItemsCount      
  
        #Get fields to Update from the Source List - Skip Read only, hidden fields, content type and attachments
        $SourceListFields = Get-PnPField -List $SourceList -Connection $SourceConn | Where { (-Not ($_.ReadOnlyField)) -and (-Not ($_.Hidden)) -and ($_.InternalName -ne  "ContentType") -and ($_.InternalName -ne  "Attachments") }

        #Loop through each item in the source and Get column values, add them to Destination
        [int]$Counter = 1
        ForEach($SourceItem in $SourceListItems)
        {  
            $ItemValue = @{}
            #Map each field from source list to Destination list
            Foreach($SourceField in $SourceListFields)
            {
                #Check if the Field value is not Null
                If($SourceItem[$SourceField.InternalName] -ne $Null)
                {
                    #Handle Special Fields
                    $FieldType  = $SourceField.TypeAsString                    
  
                    If($FieldType -eq "User" -or $FieldType -eq "UserMulti") #People Picker Field
                    {
                        $PeoplePickerValues = $SourceItem[$SourceField.InternalName] | ForEach-Object { $_.Email}
                        $ItemValue.add($SourceField.InternalName,$PeoplePickerValues)
                    }
                    ElseIf($FieldType -eq "Lookup" -or $FieldType -eq "LookupMulti") # Lookup Field
                    {
                        $LookupIDs = $SourceItem[$SourceField.InternalName] | ForEach-Object { $_.LookupID.ToString()}
                        $ItemValue.add($SourceField.InternalName,$LookupIDs)
                    }
                    ElseIf($FieldType -eq "URL") #Hyperlink
                    {
                        $URL = $SourceItem[$SourceField.InternalName].URL
                        $Description  = $SourceItem[$SourceField.InternalName].Description
                        $ItemValue.add($SourceField.InternalName,"$URL, $Description")
                    }
                    ElseIf($FieldType -eq "TaxonomyFieldType" -or $FieldType -eq "TaxonomyFieldTypeMulti") #MMS
                    {
                        $TermGUIDs = $SourceItem[$SourceField.InternalName] | ForEach-Object { $_.TermGuid.ToString()}                    
                        $ItemValue.add($SourceField.InternalName,$TermGUIDs)
                    }
                    Else
                    {
                        #Get Source Field Value and add to Hashtable                        
                        $ItemValue.add($SourceField.InternalName,$SourceItem[$SourceField.InternalName])
                    }
                }
            }
            #Copy Created by, Modified by, Created, Modified Metadata values
            $ItemValue.add("Created", $SourceItem["Created"]);
            $ItemValue.add("Modified", $SourceItem["Modified"]);
            $ItemValue.add("Author", $SourceItem["Author"].Email);
            $ItemValue.add("Editor", $SourceItem["Editor"].Email);

            Write-Progress -Activity "Copying List Items:" -Status "Copying Item ID '$($SourceItem.Id)' from Source List ($($Counter) of $($SourceListItemsCount))" -PercentComplete (($Counter / $SourceListItemsCount) * 100)
            
            #Copy column value from Source to Destination
            $NewItem = Add-PnPListItem -List $DestinationList -Values $ItemValue
  
            #Copy Attachments
            Copy-SPOAttachments -SourceItem $SourceItem -DestinationItem $NewItem
  
            Write-Host "Copied Item ID from Source to Destination List:$($SourceItem.Id) ($($Counter) of $($SourceListItemsCount))"
            $Counter++
        }
    }
    Catch {
        Write-host -f Red "Error:" $_.Exception.Message 
    }
}
  
#Set Parameters
$SourceSiteURL = "https://crescentintranet.sharepoint.com/sites/Marketing/"
$SourceListName = "Projects"
 
$DestinationSiteURL = "https://crescentintranet.sharepoint.com/sites/Sales"
$DestinationListName = "Projects"
 
#Connect to Source and destination sites
$SourceConn = Connect-PnPOnline -Url $SourceSiteURL -UseWebLogin -ReturnConnection
$SourceList = Get-PnPList -Identity $SourceListName -Connection $SourceConn
 
$DestinationConn = Connect-PnPOnline -Url $DestinationSiteURL -UseWebLogin -ReturnConnection
$DestinationList = Get-PnPList -Identity $DestinationListName -Connection $DestinationConn
  
#Call the Function to Copy List Items between Lists
Copy-SPOListItems -SourceList $SourceList -DestinationList $DestinationList

If you are copying list items between sites, make sure all parent lookup lists are already created in the target site first!