Report-CustomActionUsage.ps1

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<#
 .SYNOPSIS
  Scan all site collections within the tenant to generate a report on every site-scoped custom action.
  Generates a CSV report containing details about every custom action that was found. 

 .DESCRIPTION
  Scan all site collections within the tenant to generate a report on every site-scoped custom action.
  Generates a CSV report containing details about every custom action that was found. 

  NOTE: This script requires the PowerShell module 'SharePointPnPPowerShellOnline' to be installed. If it is missing, the script will attempt to install it.

  RECOMMENDATION: Add administrator username and password for your tenant to Windows Credential Manager before running script. 
  https://github.com/SharePoint/PnP-PowerShell/wiki/How-to-use-the-Windows-Credential-Manager-to-ease-authentication-with-PnP-PowerShell

  .PARAMETER TenantRootSiteUrl
  SharePoint Tenant Root Site URL

 .EXAMPLE
  .\Report-CustomActionUsage.ps1 -TenantRootSiteUrl "https://tenant.sharepoint.com"

  Scan all site collections within the tenant and generate a CSV report containing every site-scoped custom action.
#>

param(
  [parameter(Mandatory = $true)]$TenantRootSiteUrl
)

#############################################

$module = Get-Module -Name SharePointPnPPowerShellOnline -ListAvailable
if ($null -eq $module) {
  Write-Output "Installing PowerShell Module: SharePointPnPPowerShellOnline"
  Install-Module -Name SharePointPnPPowerShellOnline -Force -AllowClobber -Confirm:$false
}

Import-Module -Name SharePointPnPPowerShellOnline -WarningAction Ignore

#############################################

Write-Host "Connecting to Tenant Root Site URL: $TenantRootSiteUrl"
Connect-PnPOnline -Url $TenantRootSiteUrl 

$excludedTemplates = @("SPSMSITEHOST#0")        #MySite Host
$excludedTemplates += "GROUP#0"                 #Modern Group Site
$excludedTemplates += "SITEPAGEPUBLISHING#0"    #Modern Communication Site
$excludedTemplates += "STS#3"                   #Modern Team Site (not group connected)

Write-Host "Fetching list of all Site Collections"
$sites = Get-PnPTenantSite | Where-Object { $excludedTemplates -notcontains $_.Template }

Write-Host "Found $($sites.Count) Site Collections"
$timestamp = (Get-Date).ToString("yyyyMMdd.HHmm")
$csvName = "CustomActionUsage-$timestamp.csv"

foreach ($site in $sites) {
  Write-Host " SITE: $($site.Url)"
  Connect-PnPOnline -Url $site.Url
    
  $customActions = @(Get-PnPCustomAction -Scope Site)

  if ($customActions.Count -gt 0) {
    Write-Host "   Found $($customActions.Count) custom actions"
  
    foreach ($customAction in $customActions) {
      $reportRow = @{
        SiteUrl       = $site.Url
        CALocation    = $customAction.Location
        CAId          = $customAction.Id
        CAName        = $customAction.Name
        CADescription = $customAction.Description
        CAScriptBlock = $customAction.ScriptBlock
        CAScriptSrc   = $customAction.ScriptSrc
        CASequence    = $customAction.Sequence
        CAGroup       = $customAction.Group
      }
    
      ([PSCustomObject]$reportRow) | Export-Csv -Path $csvName -NoTypeInformation -Append
    }
  }
}