SharePoint 2019 to Online Migration Guide for 2026

SharePoint 2019 to SharePoint Online: The Complete Migration Guide

SharePoint Server 2019 entered extended support in 2024 and will reach end of support in October 2026. Organizations still running on-premises SharePoint 2019 face an urgent migration timeline. Beyond the support deadline, the feature gap between on-premises and online continues to widen, with Copilot, AI-powered search, Loop components, and Viva integration available only in SharePoint Online.

This guide provides a practical, phase-by-phase migration framework based on our experience migrating organizations with 1,000 to 50,000 users from on-premises SharePoint to Microsoft 365.

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Migration Assessment

Content Inventory

Before planning the migration, you need a complete picture of what exists in your on-premises environment. Run a comprehensive discovery using the SharePoint Migration Assessment Tool (SMAT) from Microsoft, third-party tools like ShareGate or Quest, or PowerShell scripts against the SharePoint farm.

What to inventory:

• Total number of site collections and sites
• Total content volume in gigabytes or terabytes
• Number of content databases and their sizes
• Custom solutions (WSPs, sandbox solutions, farm solutions)
• Custom workflows (SharePoint Designer, Visual Studio, Nintex)
• InfoPath forms and Form Library usage
• Custom master pages and page layouts
• Third-party add-ons and integrations
• External data connections (BCS, SQL, SAP)

Identity Assessment

The most complex part of any migration is identity mapping. On-premises SharePoint uses Active Directory domain accounts. SharePoint Online uses Azure Active Directory (now Microsoft Entra ID). Every user, group, and permission assignment must be mapped from on-premises AD to Azure AD.

Identity mapping steps:

• Export all users and groups referenced in SharePoint permissions
• Map each on-premises account to its Azure AD equivalent
• Identify accounts that do not exist in Azure AD (former employees, service accounts, external vendors)
• Decide how to handle unmapped accounts (create new Azure AD accounts, map to a placeholder, or remove permissions)
• Validate the mapping with a test migration of a sample site

Customization Assessment

Custom solutions are the highest-risk element of any migration. Categorize every customization by migration path.

Direct migration possible: Content types, columns, views, list templates, and site templates all migrate to SharePoint Online with standard migration tools.

Rebuild required: SharePoint Designer workflows must be rebuilt in Power Automate. InfoPath forms must be rebuilt in Power Apps. Custom web parts must be rebuilt as SPFx web parts. Custom master pages and page layouts are not supported in modern SharePoint.

Retire or replace: Some customizations should be retired rather than migrated. Evaluate each one for current business value before investing in rebuilding.

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Migration Tool Selection

SharePoint Migration Tool (SPMT)

Microsoft's free migration tool. Best for small to medium migrations up to 100 GB. Supports incremental migration. Limited scheduling and reporting capabilities. Runs on a Windows machine with access to both environments.

Migration Manager in SharePoint Admin Center

Cloud-based migration management. Supports scanning, scheduling, and monitoring. Better reporting than SPMT. Suitable for larger migrations with multiple administrators. Requires installing an agent on premises.

Third-Party Tools

For enterprise migrations exceeding 1 TB or with complex requirements, third-party tools provide superior capabilities.

ShareGate offers a desktop application with a drag-and-drop interface, pre-migration reports identifying issues, permission mapping and transformation, incremental migration support, and PowerShell automation for scripted migrations. It is our recommended tool for mid-size migrations.

Quest Metalogix provides enterprise-grade migration with granular scheduling, content transformation during migration, extensive pre-migration validation, and centralized management for distributed teams.

AvePoint delivers cloud-based migration management with strong compliance features, particularly suited for regulated industries where audit trails and chain-of-custody documentation are required.

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Migration Architecture

Hybrid Configuration

Before migrating content, establish hybrid connectivity between your on-premises farm and Microsoft 365. Hybrid search allows users to find content in both environments from a single search box. Hybrid sites provide a unified site list. Hybrid OneDrive redirects users to OneDrive for Business in the cloud.

```powershell

# Configure hybrid search (run on SharePoint Server)

New-SPAzureAccessControlServiceApplicationProxy -Name "ACS" -MetadataServiceEndpointUri "https://accounts.accesscontrol.windows.net/metadata/json/1"

```

Network Planning

Migration speed depends entirely on network bandwidth between your on-premises environment and Microsoft 365. Calculate your migration window based on content volume and available bandwidth.

Bandwidth calculation:

```

Content to migrate: 5 TB (5,120 GB)

Available bandwidth: 1 Gbps dedicated

Effective throughput: ~400 Mbps (50% of theoretical)

Transfer rate: 50 MB/s = 180 GB/hour

Migration time: 5,120 / 180 = ~28.5 hours of continuous transfer

```

Add overhead for metadata processing, permission mapping, and verification. A 5 TB migration typically takes 3-5 days with standard enterprise bandwidth. Plan migration windows during off-hours to minimize impact on network performance.

Migration Waves

Break the migration into waves of 50-200 GB each. This approach allows validation between waves, reduces risk of catastrophic failures, enables user testing and feedback, and supports a phased communication plan.

Recommended wave structure:

• Wave 0 (Pilot): 2-3 non-critical sites, 10-50 users. Validate tools, process, and identity mapping.
• Wave 1: Low-complexity sites with minimal customization. Build team confidence and refine the process.
• Wave 2-N: Progressively more complex sites. Each wave incorporates lessons from previous waves.
• Final Wave: Most complex sites with critical customizations, highest user counts, and tightest uptime requirements.

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Content Migration Execution

Pre-Migration Content Cleanup

Every terabyte you do not migrate saves days of migration time and gigabytes of cloud storage cost. Before migrating, delete files older than the retention period that have no legal hold, remove duplicate files using duplicate detection tools, archive large media files that do not need daily access, delete orphaned content in sites with no active users, and clean up version history to keep only the most recent 50-100 versions.

Permission Migration

Permissions are the most error-prone aspect of content migration. Follow these steps in order: validate the identity mapping against a sample site, run a test migration of one site with full permission mapping, compare source and target permissions using a permissions audit script, resolve any mapping failures before proceeding, and document the permission migration results for compliance audit.

Large File Handling

SharePoint Online has a 250 GB file size limit, up from 15 GB in earlier years. However, files larger than 15 GB require special handling by migration tools and may take significantly longer to transfer. Identify files over 10 GB before migration and plan for extended transfer times.

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Post-Migration Validation

Content Integrity Checks

After each migration wave, validate that the correct number of files migrated (source count equals target count), file sizes match between source and target, metadata values transferred correctly, permissions are correctly applied, and version history is preserved as expected.

User Acceptance Testing

Assign UAT testers from each department to verify their content is accessible and correct. Provide a checklist covering file access, search results, permission validation, workflow functionality, and navigation.

DNS and URL Redirects

Users will have bookmarks and links pointing to on-premises URLs. Configure URL redirects from old on-premises URLs to new SharePoint Online URLs. Use Azure Front Door or a reverse proxy to handle redirect mapping during the transition period.

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Cutover Planning

Communication Plan

Notify users at least two weeks before their content migrates. Provide clear information on what is changing, when it is changing, where to find their content after migration, who to contact for support, and training resources for SharePoint Online.

Cutover Weekend

For the final cutover of each wave, set SharePoint on-premises to read-only on Friday evening, run the final incremental migration sync overnight, validate content integrity Saturday morning, update DNS and redirects Saturday afternoon, and open SharePoint Online for users Monday morning.

Rollback Plan

Document a rollback procedure for each wave. If critical issues are discovered, you need the ability to revert users to the on-premises environment while issues are resolved. Keep the on-premises environment available in read-only mode for at least 30 days after cutover.

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Decommissioning On-Premises

After all content is migrated and validated, and users have operated successfully in SharePoint Online for 30-90 days, begin decommissioning the on-premises farm. Export a final backup of all content databases, archive the backup to long-term storage for legal hold compliance, remove the SharePoint farm servers from Active Directory, release the server resources (VMs, storage, licenses), and update documentation to reflect the new architecture.

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Frequently Asked Questions

Can I migrate directly from SharePoint 2019 to SharePoint Online without hybrid?

Yes, hybrid is optional but recommended. It provides a better user experience during the transition period by unifying search and navigation. Direct migration without hybrid works fine for smaller organizations willing to do a hard cutover.

What about Nintex workflows?

Nintex offers a migration path from Nintex for SharePoint to Nintex for Microsoft 365. Alternatively, you can rebuild workflows in Power Automate. Evaluate each workflow individually to determine the best path.

How long does a typical enterprise migration take?

For a 5,000-user organization with 10 TB of content and moderate customization, plan for 12-16 weeks from assessment to decommissioning. Larger or more complex environments can take 6-12 months.

Will search behavior change after migration?

Yes. SharePoint Online uses Microsoft Search, which provides AI-powered relevance, natural language queries, and personalized results. Most users find it superior to on-premises search, but custom search configurations (result sources, query rules, display templates) must be rebuilt.

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For help planning and executing your SharePoint 2019 to Online migration, [contact our migration team](/contact) for an assessment. We have migrated organizations with up to 50,000 users and petabytes of content. Explore our [SharePoint migration services](/services/sharepoint-migration) for details on our proven migration methodology.