List of all users alerts in SharePoint 2013

Get the site collection level users alerts:-

 Add-PSSnapin microsoft.sharepoint.powershell

 $site = Get-SPSite "http://test/sites/spalerts/"

 $alertResultsCollection = @()

 foreach ($web in $site.AllWebs) {  

     foreach ($alert in $web.Alerts){

         $alertURL = $web.URL + "/" + $alert.ListUrl

         $alertResult = New-Object PSObject

         $alertResult | Add-Member -type NoteProperty -name "List URL" -value $alertURL

         $alertResult | Add-Member -type NoteProperty -name "Alert Title" -value $alert.Title

         $alertResult | Add-Member -type NoteProperty -name "Alert Type" -value $alert.AlertType

         $alertResult | Add-Member -type NoteProperty -name "Subscribed User"-value $alert.User

         $alertResultsCollection += $alertResult

      }

  }

  $site.Dispose()

  $alertResultsCollection

  

  ## Export to CSV

  $alertResultsCollection | Export-CSV "Alerts.csv"