Understanding Password Synchronization Methods: Password-Through vs. Password Hash Synchronization
Temesghen Shama

Understanding Password Synchronization Methods: Password-Through vs. Password Hash Synchronization

In today’s hybrid IT environments, where both on-premises and cloud services are used, managing user authentication securely and reliably is essential. Two common methods of syncing passwords from on-prem Active Directory (AD) to Azure Active Directory (Azure AD) are Password-Through Synchronization (also known as Pass-through Authentication) and Password Hash Synchronization.

This article breaks down the difference between the two in simple terms and explains what happens when your AD server goes down.


🟦 What Is Password-Through Synchronization?

Password-through synchronization means that when a user logs into a cloud service like Microsoft 365, Azure AD checks the password by contacting your on-premises AD in real-time.

  • The user enters their password.
  • Azure AD sends the password securely to your local AD.
  • Your on-prem AD verifies it and sends back a response.

✅ Pros:

  • Centralized password validation using local policies (like lockout, smart card, etc.)
  • Password is not stored in Azure AD.

❌ Cons:

  • Requires your AD to be online all the time.
  • If AD is down, users cannot log in to cloud services.


🟩 What Is Password Hash Synchronization?

Password hash synchronization works differently. It copies a scrambled version (hash) of the password from your on-prem AD to Azure AD.

  • The password is never sent in plain text.
  • Only the hash is stored in Azure AD.
  • Azure AD can verify login attempts on its own.

✅ Pros:

  • Users can log in even if on-prem AD is down.
  • Simpler and more resilient for cloud authentication.
  • No real password is stored — just a non-reversible hash.

❌ Cons:

  • Local policies like smart card or account lockout won’t apply in Azure AD.
  • Some organizations prefer not to sync hashes for compliance reasons.


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🧠 Final Thoughts

Choosing between password-through and password-hash synchronization depends on your organization’s needs:

  • If you require real-time policy enforcement and strong local control, go with password-through.
  • If you want cloud reliability and offline AD backup, password hash sync is your friend.

For many, a hybrid setup using both methods (with password hash sync as a backup to pass-through) gives the best of both worlds.

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