Types of Active Directory Synchronization with Microsoft Entra ID

Before configuring hybrid identity, understand the difference between the synchronization tool and the user sign-in method. Your choice affects security, availability, administration, and user experience.

1. Microsoft Entra Connect Sync

Microsoft Entra Connect Sync is the traditional on-premises synchronization tool. It runs on a Windows Server and supports advanced hybrid environments, including multiple AD forests, Exchange hybrid deployments, device synchronization, and selected writeback features.

Best for: Organizations with complex AD environments or advanced hybrid requirements.

2. Microsoft Entra Cloud Sync

Microsoft Entra Cloud Sync uses lightweight provisioning agents installed on one or more on-premises servers. Configuration is managed mainly from the Microsoft Entra admin center, reducing the need to manage a full synchronization engine server.

Best for: Simpler environments, new deployments, and organizations that want cloud-managed configuration. Check feature compatibility before choosing it, because some advanced Entra Connect capabilities may not be available.

3. Password Hash Synchronization (PHS)

Password Hash Synchronization sends a securely transformed version of each user’s password hash to Microsoft Entra ID. Users sign in to cloud services using the same password they use on-premises.

• Pros: Simple, resilient, low maintenance, and continues to support cloud sign-in if the on-premises network is unavailable.
• Cons: Some organizations may have policy requirements that prevent cloud password-hash storage.

4. Pass-Through Authentication (PTA)

With Pass-Through Authentication, Microsoft Entra ID validates a sign-in request against an on-premises authentication agent. Password validation stays connected to the on-premises AD environment.

• Pros: Password validation occurs on-premises and no password hash is synchronized to the cloud.
• Cons: Requires healthy, available authentication agents and reliable connectivity to on-premises AD.

5. Federation with AD FS or a Third-Party Identity Provider

Federation redirects sign-in requests to an on-premises federation service, such as Active Directory Federation Services (AD FS), or a third-party identity provider.

• Pros: Supports highly customized authentication policies and specialized compliance requirements.
• Cons: Most complex option; requires more infrastructure, monitoring, certificates, and disaster-recovery planning.

6. Writeback Synchronization

Writeback is a reverse synchronization feature that sends selected cloud changes back to on-premises Active Directory. Examples can include password writeback and, in supported configurations, group or device writeback.

Important: Writeback features should be enabled only when there is a clear business need, because they introduce additional permissions and operational risk.

Recommended option for most businesses: Use Microsoft Entra Connect Sync with Password Hash Synchronization. It is generally the easiest hybrid identity model to operate, offers strong resilience, and reduces dependence on on-premises authentication infrastructure.