Microsoft Office 365's SharePoint Online Migration Tool

With Microsoft's SharePoint Migration Tool, users or administrators can automate the migration of files from file servers and on-premises SharePoint document libraries to Office 365.

Migrate from either on-premises SharePoint Server 2013 site or from a local file share or network path.

Features include:

• Incremental migrations
• Migrate hidden files...or not
• Migrate all, none, or limit the number of file versions
• Bulk migrate from multiple sources with CSV file

• Exclude:
• Specific file extensions
• files and folders with invalid characters

Permissions Migration

The location of your on-premises data and whether you have synchronized your Active Directory accounts to Azure Active Directory (AAD), can affect the permission settings on your files after they have been migrated to SharePoint Online.

To maintain existing on-premises file permissions, there must be a corresponding user in SPO. Although you can upload a custom user mapping file to the SharePoint Migration Tool, the simplest  way is to synchronize your Active Directory accounts to Azure Active Directory (AAD).

Migrating from a File Share

• There are only two types of permissions that will be migrated; Read and Write, which will be converted to contribute and read.

Migrating SharePoint On Premise Files

• All the unique permissions on a file will be migrated to SPO.  
• Inherited permissions will not be migrated.

For more info see: Introducing the SharePoint Migration Tool