A successful Microsoft 365 migration is not simply a copy job. You need to decide where content belongs, which permissions survive, what cannot be translated, how users will work after cutover and how you will prove that the destination matches the approved scope.
Start with the workload, not the migration product.
1. Define the destination before moving data
Decide which material belongs in SharePoint team sites, SharePoint communication sites, OneDrive, Teams, an archive or a disposal process.
Avoid recreating an old folder estate without examining ownership, sensitivity and use. Microsoft recommends asking people to review content before migration so obsolete material can be deleted or archived. See Microsoft's migration planning guidance for SharePoint and OneDrive.
2. Build an inventory and evidence baseline
For every source, record:
- business owner and technical owner
- volume, file count and largest items
- permissions and external sharing
- versions, metadata, workflows and customisations
- regulated, sensitive or legally held content
- unsupported names, paths or file types reported by the chosen tool
Take a dated source inventory before the pilot and again before final cutover. Without a baseline, “the tool completed” can be mistaken for “everything arrived correctly”.
3. Choose the tool for the source
Microsoft's SharePoint Migration Tool supports specified SharePoint Server sources and can migrate content to SharePoint, OneDrive and Teams. It also provides assessment, scanning and reports.
Migration Manager is managed from the SharePoint admin centre and uses agents for file shares and supported cloud sources.
Third-party tools may add scheduling, restructuring, reporting or broader source support. Do not choose from a feature table alone. Run a representative pilot and obtain current written answers about the exact source, metadata, permissions, versions and workflow types you need.
Required roles differ by tool and source. Microsoft's tools require source read access and an appropriate SharePoint, OneDrive or Global Administrator role at the destination. Use a dedicated migration account and least privilege where the tool supports it.
4. Map identity and permissions explicitly
Create a mapping for users, groups, guests and accounts that no longer exist.
Decide what happens when a source account has no destination identity, a nested group appears, unique item permissions have grown without an owner, a guest should lose access or a site needs a new owner.
Permission success means testing as ordinary destination users, not merely seeing group names in a report.
5. Run a representative pilot
Choose content that includes long paths, large files, metadata, versions, unusual permissions, pages, links and business processes.
Record the tool version, settings, filters, source snapshot and output reports. After migration, verify:
- counts and sizes within the documented scope
- a sample of file contents and versions
- metadata and dates that matter to the business
- access and denial for representative users
- navigation, links, search and connected workflows
Fix the mapping or process, then repeat the pilot. Do not explain away errors that will multiply in a later wave.
6. Plan coexistence and cutover
Specify when the source becomes read-only, how final changes are captured and where users should work during the transition.
Communicate destination links, changed behaviours, ownership and the support route. Adoption is a separate outcome from data transfer. A migration report cannot prove that people know where to work.
7. Reconcile and retain evidence
Keep migration reports, approved exceptions and validation results for each wave. Give unresolved items an owner and deadline.
Rollback usually has a boundary. You may be able to reopen the old source, but changes made in both systems will not reconcile themselves. State that limit before cutover.
This plan proves that the agreed sample and reconciliation checks passed. It does not prove regulatory compliance, complete semantic equivalence between platforms or future user adoption.
For practical help with SharePoint destinations, permissions and migration decisions, join the SharePoint & Teams Admins Space.