In post we will see how to get the sub site details in a site collection in SharePoint online using  power shell and save the details in .csv file

Make sure the SDK  SharePoint Online Client Components SDK was installed in the system
1) Create a folder( with name Get all Site Collection Info)  in  one of the local drive.

2) copy the Microsoft.SharePoint.Client.dll and  Microsoft.SharePoint.Client.Runtime.dll to that folder. we will find the dlls in the location C:\Program Files\Common Files\microsoft shared\Web Server Extensions\16\ISAPI    after installing the SDK

3) copy the below  script to notepad and save the file  with  Get all Site Collection Info.ps1

#Add - PSSnapin Microsoft.SharePoint.PowerShell  

$host.Runspace.ThreadOptions = "ReuseThread" 

#Definition of the function that allows to create a new view in a SharePoint Online list 

function Get-SubSiteCollectionInfo
{
    param ($sCSOMPath,$sSiteUrl,$sUserName,$sPassword,$sWeburl,$FileName)
    try
    {
        #Adding the Client OM Assemblies
        $sCSOMRuntimePath=$sCSOMPath +  "\Microsoft.SharePoint.Client.Runtime.dll"
        $sCSOMPathdll=$sCSOMPath +  "\Microsoft.SharePoint.Client.dll"
        Add-Type -Path $sCSOMPathdll
        Add-Type -Path $sCSOMRuntimePath        

        #SPO Client Object Model Context
        $spoCtx = New-Object Microsoft.SharePoint.Client.ClientContext($sSiteUrl)
        $spoCredentials = New-Object Microsoft.SharePoint.Client.SharePointOnlineCredentials($sUserName, $sPassword)
        $spoCtx.Credentials = $spoCredentials       

		$web = $spoCtx.Web
		$spSites = $web.Webs 

		$spoCtx.Load($web)
		$spoCtx.Load($spSites)
		$spoCtx.ExecuteQuery() 

		$AllSites = @()

		foreach ($webitem in $spSites)
		{
			$AllSites = New-Object -TypeName PSObject -Property @{
								  SiteID = $webitem.ID
								  SiteName = $webitem.Title
								  SiteUrl = ($sWeburl+$webitem.ServerRelativeUrl)
								 } | Select  SiteID,SiteName,SiteUrl
			$AllSites| Export-CSV ($sCSOMPath+"\"+$FileName+".csv") -NoTypeInformation -Append
			Get-SubSiteCollectionInfo -sCSOMPath $sCSOMPath -sSiteUrl ($sWeburl+$webitem.ServerRelativeUrl) -sUserName $sUserName -sPassword $sPassword  -sWeburl $sWeburl -FileName $FileName
		} 

        $spoCtx.Dispose()
    }
    catch [System.Exception]
    {
		$FailedSite = @()
		$FailedSite += New-Object -TypeName PSObject -Property @{
								SiteUrl =$sSiteUrl
								Exception=$_.Exception.Message
            					} | Select  SiteUrl,Exception

		$FailedSite| Export-CSV ($sCSOMPath+"\"+$FileName+"_Failed.csv") -NoTypeInformation -Append #-Encoding UTF8

        Write-Host -ForegroundColor Red $_.Exception.ToString()
		#Read-Host -Prompt "Operation failed..! Press any key to close this"
    }
} 

function Get-SiteCollectionInfo
{
    param ($sCSOMPath,$sSiteUrl,$sUserName,$sPassword,$sWeburl,$FileName)
    try
    {
        #Adding the Client OM Assemblies
        $sCSOMRuntimePath=$sCSOMPath +  "\Microsoft.SharePoint.Client.Runtime.dll"
        $sCSOMPathdll=$sCSOMPath +  "\Microsoft.SharePoint.Client.dll"
        Add-Type -Path $sCSOMPathdll
        Add-Type -Path $sCSOMRuntimePath        

        #SPO Client Object Model Context
        $spoCtx = New-Object Microsoft.SharePoint.Client.ClientContext($sSiteUrl)
        $spoCredentials = New-Object Microsoft.SharePoint.Client.SharePointOnlineCredentials($sUserName, $sPassword)
        $spoCtx.Credentials = $spoCredentials
        Write-Host "Getting All Sub Sites in a Site Collection "
		Write-Host "-------------------------------------------"

		$web = $spoCtx.Web
		$spSites1 = $web.Webs 

		$spoCtx.Load($web)
		$spoCtx.Load($spSites1)
		$spoCtx.ExecuteQuery() 

		$AllSites1 = @()

		foreach ($webitem in $web)
		{
			$AllSites1 = New-Object -TypeName PSObject -Property @{
								  SiteID = $webitem.ID
								  SiteName = $webitem.Title
								  SiteUrl = $sSiteUrl
             					 } | Select  SiteID,SiteName,SiteUrl
		}
		$AllSites1| Export-CSV ($sCSOMPath+"\"+$FileName+".csv") -NoTypeInformation -Append 

		foreach ($webitem1 in $spSites1)
		{
			$AllSites1 = New-Object -TypeName PSObject -Property @{
								  SiteID = $webitem1.ID
								  SiteName = $webitem1.Title
								  SiteUrl = ($sWeburl+$webitem1.ServerRelativeUrl)
             					 }  | Select  SiteID,SiteName,SiteUrl

			$AllSites1| Export-CSV ($sCSOMPath+"\"+$FileName+".csv") -NoTypeInformation -Append 

			Get-SubSiteCollectionInfo -sCSOMPath $sCSOMPath -sSiteUrl ($sWeburl+$webitem1.ServerRelativeUrl) -sUserName $sUserName -sPassword $sPassword  -sWeburl $sWeburl -FileName $FileName
		} 

		Read-Host -Prompt "file created Successfull..! in the following path $sCSOMPath, Press any key to close this window"
        $spoCtx.Dispose()
    }
    catch [System.Exception]
    {
        Write-Host -ForegroundColor Red $_.Exception.ToString()
		Read-Host -Prompt "Operation failed..! Press any key to close this"
    }
} 

$scriptpath = $MyInvocation.MyCommand.Path
$dir = Split-Path $scriptpath

$FileName= "Source_SiteCollection"          #Read-Host -Prompt "Enter File Name to write (eg: XXXXX)"
$sWeburl = "https://tarun.sharepoint.com"        #Read-Host -Prompt "Enter Root Site URL (eg: http://Server:port/)"
$sUserName = "admin@tarun.onmicrosoft.com"            #Read-Host -Prompt "Enter User Name"
$sPassword = ConvertTo-SecureString "XXXX" -AsPlainText -Force                #Read-Host -Prompt "Enter your password" -AsSecureString
$sSiteUrl = "https://tarun.sharepoint.com/sites/sharepointmates"    #Read-Host -Prompt "Enter Site Collection URL (eg: http://Server:port/Sites/Dev)" 

Get-SiteCollectionInfo -sCSOMPath $dir -sSiteUrl $sSiteUrl -sUserName $sUserName -sPassword $sPassword  -sWeburl $sWeburl -FileName $FileName

Note: please update the  $sWeburl,$sUserName,$sPassword  and $sSiteUrl  variables with your SharePoint online  environment.

6)Now the folder will look like this

5)Now Right click on the Get all Site Collection Info Power shell script on  select Run with PowerShell

6) After Successful execution of the  scripts we will get the below message

7) Now go to the folder, we will find the  excel file.

8) Open the excel, We will  find all the details  of the sub sites in the excel file as below

On Premises:

For On premises we need to slightly change  $spoCredentials  and $sUserName    variables in the above script.

$spoCredentials = New-Object System.Net.NetworkCredential($sUserName, $sPassword)

We need to give the user name along with domain name as below

$sUserName = "2013dev\spadmin"

Please change the  on premises site  collection url , web url  and password as well.