SharePoint Online: Find All Large Lists and Generate Report using PowerShell

#Load SharePoint CSOM Assemblies
Add-Type -Path "C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\16\ISAPI\Microsoft.SharePoint.Client.dll"
Add-Type -Path "C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\16\ISAPI\Microsoft.SharePoint.Client.Runtime.dll"

#Config Parameters
$SiteURL="https://crescent.sharepoint.com"
$ReportOutput="C:\temp\LargeLists.csv"
$Threshold=5000

#Exclude system lists
$ExcludedLists = @("App Packages","appdata","appfiles","Apps in Testing","Cache Profiles","Composed Looks","Content and Structure Reports","Content type publishing error log","Converted Forms",
 "Device Channels","Form Templates","fpdatasources","Get started with Apps for Office and SharePoint","List Template Gallery", "Long Running Operation Status","Maintenance Log Library"
 ,"Master Docs","Master Page Gallery","MicroFeed","NintexFormXml","Quick Deploy Items","Relationships List","Reusable Content","Search Config List", "Solution Gallery",
 "Suggested Content Browser Locations","TaxonomyHiddenList","User Information List","Web Part Gallery","wfpub","wfsvc","Workflow History","Workflow Tasks")

#Delete the Output Report, if exists
if (Test-Path $ReportOutput) {  Remove-Item $ReportOutput }

#Setup Credentials
$Cred= Get-Credential
$Credentials = New-Object Microsoft.SharePoint.Client.SharePointOnlineCredentials($Cred.Username, $Cred.Password)

Function Get-SPOLargeLists($SiteURL)
{
    Write-host "Processing Web:"$SiteURL
    Try {
            #Setup the context
            $Ctx = New-Object Microsoft.SharePoint.Client.ClientContext($SiteURL)
            $Ctx.Credentials = $Credentials

            #Get the web from given URL and its subsites
            $Web = $Ctx.web
            $Ctx.Load($Web)
            $Ctx.Load($web.Webs)
            $Ctx.executeQuery()

            #Get all lists from the web
            $Lists = $Ctx.Web.Lists
            $Ctx.Load($Lists)
            $Ctx.ExecuteQuery()

            $LargeListsResult = @()
            #Loop through each list and get items count
            Foreach($List in $Lists)
                {
                    if($ExcludedLists -NotContains $List.Title) #Exclude certain Lists
                       {
                        if($List.ItemCount -gt $Threshold)
                              {
                                #Get the Result to a psobject
                                $Result = New-Object PSObject
                                $Result | Add-Member NoteProperty Title($List.Title)
                                $Result | Add-Member NoteProperty URL($web.URL)
                                $Result | Add-Member NoteProperty Count($List.ItemCount)
                    
                                #Add the result to an Array
                                $LargeListsResult += $Result

                                Write-host "Found List '$($List.Title)' with $($List.ItemCount) Items" -f Yellow
                                }
                        }
                }

                #Export the result Array to CSV file
                $LargeListsResult | Export-CSV $ReportOutput -NoTypeInformation -Append

                #Iterate through each subsite of the current web and call the function recursively
                foreach ($Subweb in $web.Webs)
                {
                    #Call the function recursively to process all subsites underneaththe current web
                    Get-SPOLargeLists($Subweb.url)
                }
    }
    Catch {
        write-host -f Red "Error Finding Large Lists!" $_.Exception.Message
    }
}

#Call the function with Root site URL
Get-SPOLargeLists -SiteURL $SiteURL 

#Parameters
$TenantAdminURL = "https://crescent-admin.sharepoint.com"
$CSVFile = "C:\Temp\LargeLists.csv"
$Threshold = 5000
$LargeListsInventory = @()

#Function to Audit Larger lists
Function Find-PnPLargeLists($Web)
{
    Write-host "Auditing Site:"$Web.Url
    
    #Get All Lists from the Web
    Get-PnPList -web $Web | ForEach-Object {
        If($_.ItemCount -gt $Threshold)
        {
            Write-host "`tFound a Larger list '$($_.Title)' with Items:"$_.ItemCount

            $LargeListsInventory += New-Object -TypeName PSObject -Property @{
                SiteURL = $Web.Url
                ListName = $_.Title
                ItemCount = $_.ItemCount
                LastModified = $_.LastItemUserModifiedDate
            }
        }
    }
    #Export Data to CSV File
    $LargeListsInventory | Export-Csv $CSVFile -NoTypeInformation -Append
}
$Cred = Get-credential
#Connect to Tenant Admin Site
Connect-PnPOnline -url $TenantAdminURL -credential $Cred

#Delete the CSVFile if exists 
If (Test-Path $CSVFile) { Remove-Item $CSVFile }

#Get All Site collections and Iterate through
$SiteCollections = Get-PnPTenantSite
ForEach($Site in $SiteCollections)
{
    #Connect to Site Collection
    $SiteConn =  Connect-PnPOnline -url $Site.URL -credential $Cred -ReturnConnection

    #Get the Root web of the Site Collection
    $RootWeb = Get-PnPWeb

    #Call function to Find Large Lists in the Web
    Find-PnPLargeLists -Web $RootWeb

    #Get All Subsites of the site collection and call the function to find large lists
    Get-PnPSubWebs -Web $RootWeb -Recurse | ForEach-Object {Find-PnPLargeLists -Web $_}

    Disconnect-PnPOnline -Connection $SiteConn
}