SharePoint Online: Unique Permissions Report using PowerShell

Requirement: Get unique permissions report in SharePoint Online using PowerShell

PowerShell for SharePoint Online Unique Permissions Report
Here is the SharePoint Online PowerShell to get unique permissions:

#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"
  
#To call a non-generic Load Method
Function Invoke-LoadMethod() {
    Param(
            [Microsoft.SharePoint.Client.ClientObject]$Object = $(throw "Please provide a Client Object"), [string]$PropertyName
         )
   $Ctx = $Object.Context
   $Load = [Microsoft.SharePoint.Client.ClientContext].GetMethod("Load") 
   $Type = $Object.GetType()
   $ClientLoad = $Load.MakeGenericMethod($Type)
   
   $Parameter = [System.Linq.Expressions.Expression]::Parameter(($Type), $Type.Name)
   $Expression = [System.Linq.Expressions.Expression]::Lambda([System.Linq.Expressions.Expression]::Convert([System.Linq.Expressions.Expression]::PropertyOrField($Parameter,$PropertyName),[System.Object] ), $($Parameter))
   $ExpressionArray = [System.Array]::CreateInstance($Expression.GetType(), 1)
   $ExpressionArray.SetValue($Expression, 0)
   $ClientLoad.Invoke($Ctx,@($Object,$ExpressionArray))
}

#Function to Get Unique Permission from a Web and its contents - recursively
Function Get-SPOUniquePermissionReport([Microsoft.SharePoint.Client.Web]$Web)
{
    Write-host -f Yellow "`nSearching Unique Permissions on the Site:"$web.Url

    #Check if the given site is using unique permissions
    Invoke-LoadMethod -Object $Web -PropertyName "HasUniqueRoleAssignments"
    $Ctx.ExecuteQuery()
     
    #Get the Root Web
    $RootWeb = $ctx.site.RootWeb
    $Ctx.Load($RootWeb)
    $Ctx.ExecuteQuery()
 
    ### Check if the web has broken inheritance
    If($Web.HasUniqueRoleAssignments -and $Web.ID -ne $RootWeb.ID)
    {
        #Get Object Details and Send the Data to Report file
        $ObjectName = $Web.Title ;$ObjectType = "Sub Site" ; $ObjectURL = $Web.URL
        "$($ObjectName) `t $($ObjectURL) `t $($ObjectType)" | Out-File $CSVFile -Append
        Write-host -f Green "`t Unique Permissions Found on Site:" $Web.URL
    }
         
    ### Get unique permission in Lists
    Write-host -f Yellow "`t Searching Unique Permissions on the Lists..."
    $Lists =  $Web.Lists
    $Ctx.Load($Lists)
    $Ctx.ExecuteQuery()
 
    #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", "Style Library",
     ,"Master Docs","Master Page Gallery","MicroFeed","NintexFormXml","Quick Deploy Items","Relationships List","Reusable Content","Search Config List", "Solution Gallery", "Site Collection Images",
     "Suggested Content Browser Locations","TaxonomyHiddenList","User Information List","Web Part Gallery","wfpub","wfsvc","Workflow History","Workflow Tasks", "Preservation Hold Library")
     
    #Iterate through each list
    ForEach($List in $Lists)
    {
        $Ctx.Load($List)
        $Ctx.ExecuteQuery()
 
        If($ExcludedLists -NotContains $List.Title -and $List.Hidden -eq $false)
        {
            #Check if the given site is using unique permissions
            Invoke-LoadMethod -Object $List -PropertyName "HasUniqueRoleAssignments"
            $Ctx.ExecuteQuery()
  
            #Check if List has unique permissions
            If($List.HasUniqueRoleAssignments)
            {
                #Send Data to CSV File
                $ObjectTitle = $List.Title
                $ObjectURL = $("{0}{1}" -f $Web.Url.Replace($Web.ServerRelativeUrl,''), $List.RootFolder.ServerRelativeUrl)                
                $ObjectType = "List/Library"
                "$($ObjectTitle) `t $($ObjectURL) `t $($ObjectType)" | Out-File $CSVFile -Append

                Write-host -f Green "`t`tUnique Permissions Found on the List: '$($List.Title)'"
            }
 
            Write-host -f Yellow "`t`t Searching Unique Permissions on the Lists Items of '$($List.Title)'"
            
            ### Get unique permission on List items
            Do {  
                #Get all items from the list
                $Query = New-Object Microsoft.SharePoint.Client.CamlQuery
                $Query.ViewXml = "<View Scope='RecursiveAll'><RowLimit>500</RowLimit></View>"
                $ListItems = $List.GetItems($Query)
                $Ctx.Load($ListItems)
                $Ctx.ExecuteQuery()
            
                $Query.ListItemCollectionPosition = $ListItems.ListItemCollectionPosition
   
                #Loop through each List item
                ForEach($ListItem in $ListItems)
                {
                    Invoke-LoadMethod -Object $ListItem -PropertyName "HasUniqueRoleAssignments"
                    $Ctx.ExecuteQuery()
                    If ($ListItem.HasUniqueRoleAssignments -eq $true)
                    {
                        #Send Data to CSV File
                        $ObjectType = "List Item/Folder"
                        #Get the URL of the List Item
                        Invoke-LoadMethod -Object $ListItem.ParentList -PropertyName "DefaultDisplayFormUrl"
                        $Ctx.ExecuteQuery()
                        $DefaultDisplayFormUrl = $ListItem.ParentList.DefaultDisplayFormUrl
                        $ObjectURL = $("{0}{1}?ID={2}" -f $Web.Url.Replace($Web.ServerRelativeUrl,''), $DefaultDisplayFormUrl,$ListItem.ID)
                        $ObjectTitle = $ListItem["Title"]
                        "$($ObjectTitle) `t $($ObjectURL) `t $($ObjectType)" | Out-File $CSVFile -Append

                        Write-host  -ForegroundColor Green "`t`t`t Unique Permissions Found on Item ID:" $ListItem.ID
                    }
                }
            } While ($Query.ListItemCollectionPosition -ne $null)
        }
    }
 
    #Process each subsite in the site
    $Subsites = $Web.Webs
    $Ctx.Load($Subsites)
    $Ctx.ExecuteQuery()        
    Foreach ($SubSite in $Subsites)
    {
        #Call the function Recursively
        Get-SPOUniquePermissionReport($Subsite)
    }
}
 
#Config Parameters
$SiteURL= "https://crescent.sharepoint.com/sites/marketing"
$CSVFile = "C:\Temp\UniquePermissionsRpt.csv"

#Get Credentials to connect
$Cred = Get-Credential
  
Try {
    #Setup the context
    $Ctx = New-Object Microsoft.SharePoint.Client.ClientContext($SiteURL)
    $Ctx.Credentials = New-Object Microsoft.SharePoint.Client.SharePointOnlineCredentials($Cred.UserName,$Cred.Password)
      
    #Get the Web
    $Web = $Ctx.Web
    $Ctx.Load($Web)
    $Ctx.ExecuteQuery()

    #Write CSV (TAB Separated) File Header
    "Title `t URL `t Object" | Out-File $CSVFile
     
    #Call the function to get unique permissions from the site collection
    Get-SPOUniquePermissionReport $Web
}
Catch {
    write-host -f Red "Error:" $_.Exception.Message
}

This PowerShell script gets you the list of objects such as site, list or library, list items which are having broken permission inheritance in a given site collection. If you want to get a report on who has access to what, use my another PowerShell script: SharePoint Online: Site Collection Permission Report using PowerShell.

If you need to find subsites, lists and libraries or list items with unique permissions, use below scripts: