Exclude lists in search result from sites and subsites in SharePoint using PowerShell

Requirement : 

Loop Through All Subsites in a Site Collection using PowerShell and exclude lists from search results (set property NoCrawl = True)

Manual approach to exclude lists from search index:

List Settings -> Advanced Settings -> set 'Allow items from this document library to appear in search results' to No

PowerShell Script to Iterate Through All Subsites in a Site Collection in SharePoint Online:

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$Username = "ABC@domain-name.com"

$Password = ConvertTo-SecureString -String "*******" -AsPlainText -Force

$Credentials = New-Object System.Management.Automation.PSCredential ($Username, $Password)

$targetWeb = "https://abc.sharepoint.com/sites/sitecollection" ## URL of the site you are uploading to

$clientid = "abc-abc-abc-abc-abc" #Add client id of site

$clientsecret = "abcdefghijklmnopq=" #Add client secret of site

$ListsNametoKeep = @("Employee","Students") #Skip list name from array where we want to keep list in search result

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try {

Connect-PnPOnline -Url $targetWeb -AppId $clientid -AppSecret $clientsecret

Write-Host "Connection to site established: " $targetWeb

}

catch {

Write-Error $_

}

 Get-RootSiteList

 Get-SubSiteList

  Function Get-RootSiteList()  

{  

    $rootWeb=Get-PnPWeb  

    write-host -ForegroundColor Magenta "Getting information from the website - " $rootWeb.Title " - " $rootWeb.Url  

    Get-AllLists($rootWeb);  

} 

 Function Get-AllLists($web)  

{  

 $Lists=Get-PnPList -Web $web 

    try{

          foreach($list in $Lists)  

            {  

                if(-not($list.Title -in $ListsNametoKeep))

                {

                    

                    $list.NoCrawl = $True

                    $list.Update()

                    $list.Context.ExecuteQuery()

                    Write-host $list.Title -ForegroundColor Yellow -NoNewline; Write-Host  ' - '  -ForegroundColor Cyan -NoNewline; Write-Host ' List has been Excluded from Search Index!' -f Green 

                 } 

             }

        }

     catch

         {

           write-host -f Red 'Error Excluding List ' $list.Title 'from Search Index!' $_.Exception.Message 

         }

}  

Function Get-SubSiteList()  

{  

    $websites=Get-PnPSubWebs -Recurse  

    foreach($web in $websites)  

    {      $Count++ #Print subsite count if required

        write-host -ForegroundColor Magenta "Getting information from the website - " $web.Title " - " $web.Url  

        Get-AllLists($web);  

    } 

 } 

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