Microsoft Entra Connect Sync Upgrade: 2026 Planning Guide

Microsoft Entra Connect Sync remains an important component for organizations that operate a hybrid identity environment using on-premises Active Directory Domain Services (AD DS) and Microsoft Entra ID. It provides the directory synchronization layer that connects local directory identities with Microsoft’s cloud identity platform, helping organizations maintain consistent users, groups, and selected attributes across both environments.

For organizations still using Microsoft Entra Connect Sync, 2026 introduces an important version requirement. Microsoft has announced that Microsoft Entra Connect Sync versions below 2.5.79.0 will stop working on September 30, 2026. This means organizations should not treat the upgrade as a routine software update. It should be approached as a planned identity infrastructure change with documented prerequisites, validation procedures, and recovery planning.

The upgrade is also an opportunity to review whether the existing synchronization architecture continues to meet business requirements or whether Microsoft Entra Cloud Sync should be evaluated as part of a longer-term modernization strategy.

This guide explains how organizations can prepare for the 2026 requirement, validate their environment, safely upgrade Microsoft Entra Connect Sync, and evaluate their options for future hybrid identity management.

Microsoft Entra Connect Sync is an on-premises synchronization engine that connects Active Directory Domain Services with Microsoft Entra ID.

In a typical hybrid identity environment, it can synchronize:

This synchronization allows changes made in an organization’s local Active Directory environment to reflect in Microsoft Entra ID.

For example, when a user is created, updated, moved, or removed in Active Directory, synchronization determines how that change should be represented in the cloud directory.

This makes synchronization availability important to account provisioning, access continuity, group membership, and identity lifecycle processes.

For this reason, Microsoft Entra Connect Sync should be treated as part of the organization’s identity infrastructure.

The 2026 upgrade has two objectives:

Core components and data flow

Microsoft Entra Connect Sync contains several components that work together to process directory information.

The connector space represents information associated with a connected directory. The metaverse provides a central representation of objects and attributes after synchronization rules have been applied.

Synchronization rules determine how information is transformed and processed before being exported through the Microsoft Entra connector. When reviewing attribute flow, document how source values map to their intended destination attributes and which rules govern those mappings.

A simplified data flow is:

An error at any stage can prevent an expected change from reaching Microsoft Entra ID.

Common examples include duplicate attributes, connector errors, filtering issues, permission problems, and failed exports.

Understanding this flow helps administrators troubleshoot the specific object and synchronization stage rather than repeatedly forcing synchronization without identifying the root cause.

What synchronization does not do

Microsoft Entra Connect Sync is not a backup platform or complete identity security strategy.

It does not replace:

Authentication methods also require separate planning. Organizations should evaluate their authentication architecture, security controls, and licensing requirements independently from directory synchronization.

The first priority for organizations using Microsoft Entra Connect Sync should be determining whether their installation meets Microsoft’s 2026 version requirement.

Microsoft has stated that Microsoft Entra Connect Sync versions below 2.5.79.0 will stop working on September 30, 2026.

Organizations should therefore verify the installed version rather than assume that automatic updates or previous maintenance activities have brought the environment into compliance.

The assessment should include:

The upgrade should be treated as a change-controlled identity project. A proper plan should include configuration of documentation, validation criteria, recovery procedures, and communication with teams that depend on identity services.

Inventory the current installation

Before upgrading, document the current synchronization architecture.

Record the installed Microsoft Entra Connect version, Windows Server version, SQL Server deployment model, service account configuration, connector accounts, sign-in method, source anchor, filtering configuration, custom synchronization rules, and staging-server status.

Include attribute filtering in this inventory: record which attributes are selected for synchronization and the business requirements behind those choices. Review these selections alongside object-scoping rules, so the upgrade validation covers both the intended identities and their required data.

Also identify any modifications made to configuration files such as miiserver.exe.config.

This is particularly important because an upgrade can expose configuration changes that were made previously but were never formally documented.

The objective is to create a reliable baseline of the existing environment before making changes.

Review the release history and build a safe upgrade window

Choose a maintenance window that minimizes the impact of identity changes.

Before starting the upgrade:

Success should be measurable.

For example, the organization could require a successful import, synchronization, and export cycle, no unexpected deletion activity, correct scheduler operation, and successful testing of representative identities.

Installing the correct software version is only one part of upgrade readiness.

Administrators should verify supported Windows Server versions, .NET requirements, Microsoft Entra permissions, network connectivity, proxy requirements, and other prerequisites using Microsoft’s documentation for the target release. Record the installed .NET version alongside the server inventory rather than assuming the existing environment meets the target release’s requirements.

Active Directory health should also be reviewed before making synchronization changes.

Important checks include:

Connector and installation accounts should follow least-privilege principles where supported, and account ownership should be documented.

Prepare Active Directory and Microsoft Entra ID

Directory data quality has a direct effect on synchronization.

Administrators should look for duplicate or conflicting values involving attributes such as userPrincipalName and proxyAddresses.

User principal name suffixes should be reviewed to ensure they correspond with domains that are properly configured and verified in Microsoft Entra ID.

Source anchor configuration should also be documented.

This becomes particularly important for organizations expecting future mergers, acquisitions, tenant changes, or other identity restructuring. A source of anchor decision should support the organization’s long-term identity strategy rather than simply solving an immediate synchronization requirement.

Size the server for resilience

Microsoft’s hardware recommendations provide a useful baseline for synchronization server sizing, but organizations should consider the actual characteristics of their environment.

Factors include:

Where possible, organizations should avoid placing the synchronization engine directly on a domain controller.

The server should also be incorporated into normal infrastructure operations, including security patching, monitoring, administrative access controls, and recovery planning.

Before starting the upgrade, capture the current synchronization baseline.

Record the current version, last successful synchronization, connector status, import results, synchronization results, export results, and existing errors.

Then follow the supported upgrade path for the target release.

Avoid combining the upgrade with unrelated identity configuration changes. If multiple changes are introduced simultaneously, troubleshooting becomes significantly more difficult.

After installation, validate the environment in stages.

First verify the server and synchronization service. Then review connector operations and finally confirm that expected directory changes are appearing correctly in Microsoft Entra ID.

Post-upgrade validation checklist

After the upgrade, confirm:

Synchronization Service Manager should be reviewed for connector errors, pending exports, attribute conflicts, and other warnings.

Test with representative identities

Testing should include more than one standard user.

Create a controlled test group representing the organization’s common identity scenarios.

Consider testing:

Verify expected attributes and group memberships in Microsoft Entra ID. Compare the observed attribute flow with your documented baseline, including any custom transformations and attribute filtering decisions.

Where password hash synchronization is used, validate appropriate password-change behavior using a controlled test account.

The upgrade is not the end of the project.

Organizations should establish ongoing monitoring for synchronization errors, failed exports, connector health, unexpected deletions, attribute conflicts, and scheduler failures.

Synchronization monitoring is also relevant to identity security.

For example, if an employee is removed from Active Directory, but the change does not synchronize correctly, their cloud identity could remain in an unexpected state.

Clear operational ownership is therefore essential.

Organizations should document:

Use staging mode for high availability

Staging mode provides a way to maintain a secondary Microsoft Entra Connect Sync server that can process synchronization information without exporting changes to Microsoft Entra ID.

This can provide a controlled recovery option if the primary server becomes unavailable.

A failover procedure should include:

The process should be documented and tested rather than assumed to work during an emergency.

Investigate common synchronization failures

Common synchronization problems include:

When troubleshooting, identify the affected connector, object, and synchronization stage before changing configuration or repeatedly triggering full synchronization.

Microsoft Entra Cloud Sync provides an alternative cloud-managed approach to hybrid identity synchronization.

Cloud Sync uses lightweight provisioning agents and a cloud-managed service model, while Microsoft Entra Connect Sync uses a more traditional synchronization engine installed within the organization’s environment.

The two technologies should not automatically be treated as interchangeable.

The appropriate architecture depends on:

Organizations should compare their existing requirements against Microsoft’s current supported feature set before planning a migration.

When Entra Connect Sync may remain appropriate

Connect Sync may remain appropriate when an organization depends on synchronization capabilities or configurations that do not fit its intended Cloud Sync architecture.

Potential considerations include complex synchronization requirements, custom rules, specific transformations, or certain Exchange-related dependencies.

Organizations should document each customization and determine whether the corresponding requirement is supported by Cloud Sync before planning a transition.

Regardless of the long-term direction, organizations continuing to use Connect Sync must keep it on a supported version.

When Cloud Sync may be a better fit

Cloud Sync may fit organizations that prefer a more cloud-managed synchronization architecture.

Potential fit signals include:

However, migration should be based on testing rather than assumptions.

A pilot can use a controlled organizational unit to compare object synchronization, attributes, group membership, provisioning behavior, filtering, latency, and error handling.

A structured roadmap makes it easier to manage the 2026 requirement.

Example upgrade decision path

The two organizations may therefore require different long-term strategies even though they face the same 2026 version deadline.

Common mistakes to avoid

Organizations should avoid waiting until the deadline to begin planning.

Other common mistakes include:

The safest approach is to make the upgrade measurable, controlled, and well documented.

The September 30, 2026 deadline makes Microsoft Entra Connect Sync version compliance an immediate priority for organizations still using the service.

The key considerations are:

For organizations planning broader Microsoft 365 or hybrid identity modernization, the 2026 Connect Sync requirement can also provide an opportunity to review the overall identity architecture.

The immediate objective is to remain on a supported version before the September 30, 2026 deadline. The longer-term objective is to maintain an identity environment that is resilient, supportable, secure, and aligned with the organization’s technical and business requirements.