Migrating from On-Premise Active Directory to Entra ID: What to Expect

The migration from on-premise Active Directory to Microsoft Entra ID (formerly Azure Active Directory) is one of the most consequential infrastructure transitions an IT organization can undertake. It touches identity, authentication, application access, device management, and the security architecture of the entire enterprise. Done well, it positions the organization for a cloud-first future with modern security capabilities — conditional access policies, passwordless authentication, continuous access evaluation, and rich integration with Microsoft 365 and thousands of SaaS applications — that on-premise AD simply cannot provide. Done poorly, it creates months of authentication failures, application outages, user frustration, and a credibility gap for the IT team managing the transition.

The challenge is that this migration is almost never a clean cutover. Most organizations have accumulated years of on-premise AD dependencies that don’t disappear when an organization decides to move to the cloud. Legacy applications authenticate via Kerberos or NTLM. Printers, file shares, and legacy devices are joined to the domain. Group Policy manages hundreds of workstation configurations. Third-party tools are integrated with AD via LDAP. Service accounts run on dozens of servers with domain-joined identities. Each of these dependencies must be individually assessed, migrated or replaced, or wrapped with compatibility layers that allow continued operation during the transition period — and there are always more dependencies than the initial assessment reveals.

This guide provides a realistic picture of what the migration from on-premise AD to Entra ID involves in practice: the assessment and planning work that determines success, the hybrid coexistence architecture that organizations run for anywhere from a few months at a small business to 12–36 months at a large enterprise, the application authentication migration challenges that are typically the longest workstream, the device management transition, and the organizational change management that determines whether the technical migration achieves its intended outcomes in the real world.

Start With a Thorough Environment Assessment

The foundation of a successful Entra ID migration is a thorough, honest assessment of the current on-premise AD environment. Most organizations discover during assessment that their AD environment is significantly more complex than they realized — not because it was poorly designed, but because it has been in production for a decade or more and accumulated integrations, customizations, and dependencies that were never centrally documented. The assessment needs to cover: the complete user and computer inventory and OU structure, the full Group Policy inventory with policy purposes documented, all application authentication dependencies (LDAP, Kerberos, NTLM, certificate-based), all trust relationships with other domains or forests, the complete service account inventory with associated applications, and the current device management approach including MDM enrollment status.

Microsoft provides tools to assist with this assessment — Microsoft Entra Connect Health to monitor your sync and AD FS infrastructure, the AD FS application migration dashboard in the Entra admin center to show which federated apps are in use and whether they can move to Entra ID, and the Microsoft Graph API to pull sign-in and directory data from Entra ID — but automated discovery is insufficient on its own. (The Active Directory Migration Tool, or ADMT, doesn’t belong on this list. It moves objects between AD domains and forests, not to Entra ID, and Microsoft has halted its development.) Interview the IT staff responsible for specific applications and infrastructure components. Talk to application owners, even for applications managed by external vendors. Check with the networking team for any RADIUS authentication dependencies. The dependencies you miss during assessment are the ones that cause the most disruptive failures during migration.

The output of the assessment should be a structured migration inventory: a complete catalog of AD dependencies categorized by migration approach (move to Entra ID native auth, wrap with App Proxy, replace with cloud-native alternative, retain on-premise permanently), business criticality, and migration complexity. This inventory drives the migration plan, resource estimates, and timeline projections that leadership needs to fund and support the project appropriately.

Design the Hybrid Architecture

For virtually all organizations beyond small businesses, the Entra ID migration is not a cutover event but a hybrid coexistence period, with its own rules for managing the identity lifecycle in a hybrid environment. During this period, on-premise AD and Entra ID operate simultaneously, connected by Microsoft Entra Connect (formerly Azure AD Connect), which synchronizes identities from on-premise AD to the cloud. Users have a single synchronized identity that works across both environments, authentication is handled by whichever system owns the resource being accessed, and the migration progresses workload by workload as dependencies are assessed and resolved.

The hybrid architecture design requires several key decisions before deployment. The first is the authentication method for synchronized users: Password Hash Synchronization (PHS) is the simplest and most resilient option, syncing password hashes to Entra ID so authentication can continue even if on-premise connectivity is lost; Pass-through Authentication (PTA) validates passwords against on-premise AD in real time without syncing hashes; Active Directory Federation Services (AD FS) is the most complex option and is now generally recommended only for organizations with specific federation requirements that PTA can’t meet. Microsoft now recommends PHS for most organizations due to its resilience and lower operational overhead.

The second key decision is the device join target state — Microsoft Entra hybrid joined (maintains on-premise domain join while also registering with Entra ID, required for applications that depend on on-premise domain join), Entra ID Joined (no on-premise dependency, the target state for most new devices), or a mixed fleet during the transition. Getting these architectural decisions right before deployment is dramatically cheaper than changing them mid-migration. Engage Microsoft FastTrack or a qualified Microsoft partner for architectural review before committing to a design.

Migrate Applications to Modern Authentication

Application authentication migration is typically the longest, most complex, and most business-impactful workstream in an Entra ID migration. Applications using Kerberos or NTLM authentication work seamlessly with on-premise AD but have no direct path to cloud-native authentication. Applications using LDAP for user lookup or bind authentication have similar on-premise dependencies. The migration paths for these applications are: modernize the application to support SAML 2.0 or OIDC (the cloud-native protocols natively supported by Entra ID), replace the application with a cloud-native SaaS equivalent that already supports modern auth, or use Microsoft Entra Application Proxy to provide Entra ID-managed access to the on-premise application without requiring the application itself to change.

For SaaS applications, migration is usually the most straightforward workstream. Configure SAML or OIDC federation between the SaaS application and Entra ID, test with a small pilot group, address any attribute mapping issues, and cut over users from direct authentication to federated SSO. Most modern SaaS applications support this well, and the Entra ID application gallery includes pre-configured integration templates for thousands of common SaaS tools that significantly reduce the configuration work.

For on-premise legacy applications, particularly those built on older platforms that haven’t been updated in years, the migration path is more complex and requires per-application decision-making. Some applications can be modernized through vendor-provided updates; others require custom development work to add SAML support; others are best replaced with cloud-native alternatives in a parallel workstream. Plan for this assessment and decision process to take longer than expected — application owners often overestimate their application’s migration readiness and underestimate the testing required to validate that modernization hasn’t broken existing functionality.

Manage the Device and Endpoint Transition

Device management is the other major workstream that runs in parallel with application migration. On-premise domain-joined devices managed through Group Policy and SCCM need to transition to a cloud-managed model. The typical path is through Microsoft Entra hybrid join as an intermediate state — the device maintains its on-premise domain join (preserving compatibility with any applications that require it) while also registering with Entra ID (enabling conditional access, Intune enrollment, and cloud-managed policies). As application dependencies are resolved, devices can be re-provisioned as purely Entra ID Joined, eliminating the on-premise domain dependency entirely.

The management tooling transition — from Group Policy and SCCM to Microsoft Intune — typically runs as a parallel project. Intune provides cloud-based configuration profiles, compliance policies, app deployment, and device health monitoring that replace most Group Policy and SCCM functions for modern managed devices. The Group Policy inventory from the assessment phase drives the Intune configuration profile design: each significant GPO needs a corresponding Intune policy. This mapping work is time-consuming but necessary, and it often surfaces GPOs that have outlived their purpose and can be retired rather than migrated.

Organizational Change Management Is Not Optional

The technical components of an Entra ID migration are well-documented and achievable with proper planning. The organizational change management component is where migrations more often struggle. Users will encounter changes in their authentication experience — new login prompts, MFA requirements for cloud applications, different SSO behavior — that they didn’t expect and weren’t prepared for. IT help desk volume spikes during each migration wave as users encounter these changes. If communication and training haven’t been done proactively, the user experience degradation generates organizational resistance that can slow or derail the migration.

Invest in user communication before each migration wave: what is changing, when, what the new experience will look like, and who to contact with issues. For significant changes like MFA enrollment, provide self-service enrollment tools and grace periods rather than forcing enrollment at login time. Build help desk playbooks for the most common post-migration issues so that support staff can resolve them quickly and consistently. Treat the user experience as a migration success criterion alongside the technical milestones.

Conclusion

Migrating to Entra ID can take a few months at a small business and several years at a large enterprise. Either way, it requires careful upfront planning, sustained organizational commitment, and patience with complexity that doesn’t resolve itself quickly. The organizations that succeed invest in thorough assessment before starting (application dependency mapping, device readiness, and GPO translation in particular), design a realistic hybrid architecture for the coexistence period, sequence the migration thoughtfully based on dependency analysis and business risk, and maintain clear communication with business stakeholders about progress, timeline, and what each migration wave will change for end users.

The destination — a cloud-first identity architecture with modern security capabilities, reduced on-premise infrastructure overhead, and native integration with the cloud services the business increasingly depends on — is genuinely worth the journey. The organizations that complete this migration are measurably better positioned to enforce Zero Trust security, support remote and hybrid work, and respond to identity-related security incidents than those still running entirely on-premise AD. The path is well traveled, and a structured approach that doesn’t rush the technical execution avoids most surprises. Plan well, execute carefully, and the investment pays dividends for years.

How ezOnboard Supports Azure AD Environments

ezOnboard integrates with both on-premises Active Directory and Azure AD (Microsoft Entra ID), supporting organizations at any point in their migration journey. Whether you’re managing identities on-premises, in hybrid mode, or fully in the cloud, ezOnboard’s provisioning workflows create accounts in the right identity system automatically—without requiring IT to reconfigure the onboarding process as your infrastructure evolves. For teams mid-migration, ezOnboard’s flexible integration layer ensures that onboarding and offboarding automation works correctly throughout the transition and beyond.

Frequently Asked Questions

What’s the difference between a migration to Azure AD and a hybrid AD deployment?

A full migration to Azure AD (now Microsoft Entra ID) means decommissioning your on-premises domain controllers and managing identities entirely in the cloud. A hybrid deployment keeps your on-premises AD as the source of identity truth while synchronizing accounts to Entra ID using Microsoft Entra Connect—enabling cloud services like Microsoft 365 while maintaining local authentication for on-premises resources. For most SMBs, hybrid is the realistic intermediate state; full cloud-only is the long-term target for organizations that have eliminated on-premises infrastructure entirely. The right choice depends on whether you still have on-premises applications that require Kerberos or NTLM authentication.

What are the biggest risks in an on-premises to Azure AD migration?

The primary risks are: authentication gaps for applications still relying on on-premises AD (including line-of-business apps, print servers, and file shares), user disruption if devices aren’t prepared for Microsoft Entra join before on-premises AD is decommissioned, synchronization errors that result in duplicate or mismatched accounts, and loss of Group Policy enforcement for devices that were managed through on-premises GPOs. Each of these risks is manageable with proper planning and a phased approach, but they require thorough application dependency mapping before migration begins.

How long does an AD to Azure AD migration typically take for an SMB?

For a 50 to 500 user SMB with few legacy on-premises applications, a well-planned migration runs 3 to 6 months from kickoff to full decommission of on-premises domain controllers. Larger organizations, or SMBs with many applications that depend on Kerberos, NTLM, or LDAP, should expect a longer hybrid period, often 12 to 36 months at enterprise scale. This timeline includes an assessment phase (identify dependencies, application inventory, device audit), a preparation phase (deploy Microsoft Entra Connect, configure hybrid join, test SSO for cloud apps), a migration phase (move devices to Microsoft Entra join, migrate workloads off on-premises AD), and a decommission phase (remove DC dependency from remaining services, retire domain controllers). Organizations that try to compress this timeline without thorough preparation almost always encounter the application dependency issues in the most disruptive way possible.

What happens to Group Policy after migrating to Azure AD?

Microsoft Entra ID (formerly Azure AD) does not support traditional Group Policy Objects. This is one of the most significant operational differences between on-premises AD and Entra ID. The equivalent in Entra ID is Microsoft Intune with Configuration Profiles and Compliance Policies, which replicate most GPO functionality for cloud-managed devices. Before migrating, conduct a full GPO inventory and map each setting to its Intune equivalent. Settings without a direct Intune analog require either an alternative management approach or an assessment of whether they’re still needed. This GPO-to-Intune translation is often the most labor-intensive part of the migration project.

Can you roll back an Azure AD migration if something goes wrong?

Rolling back from Azure AD to on-premises AD is technically possible but practically disruptive—it requires re-joining devices to the domain, reconfiguring application authentication, and potentially rebuilding trust relationships. The best risk mitigation is a phased migration with clear rollback criteria defined at each phase gate, not a plan to roll back the entire migration after the fact. Keep on-premises domain controllers operational and healthy throughout the migration rather than decommissioning them early; this preserves the option to reverse course at any phase without catastrophic impact.