This is a short blog post with a PowerShell cmdlet that will return you the Azure AD tenant id for a given domain.
function Get-AzureADTenantId { [CmdletBinding()] [Alias()] [OutputType([string])] Param ( # Param1 help description [Parameter(Mandatory=$true, ValueFromPipelineByPropertyName=$true, Position=0)] $DomainName ) Begin { Load-Assembly System.Xml.Linq | Out-Null } Process { $FederationMetadata = Get-AzureADFederationMetadata -Domain $DomainName $FederationMetadata.EntityDescriptor.entityID -split "/" | where{$_ -match "^[a-zA-Z0-9]{8}-[a-zA-Z0-9]{4}-[a-zA-Z0-9]{4}-[a-zA-Z0-9]{4}-[a-zA-Z0-9]{12}$"} } End { } } Get-AzureADTenantId microsoft.com Get-AzureADTenantId microsoft.onmicrosoft.com