File with a .MIG extension contains data which are a backup copy of users of a Windows system – their accounts, application’s settings and system settings, folders, files and registry entries. MIG files are used in the process of migration of user’s data between Microsoft systems or during their change.

The Windows Easy Transfer software and the USMT (Microsoft User State Migration Tool) saves data into MIG files on the local level and remotely. The first tool is used in migration of data from a single computer while the other one to perform a transfer of a large amount of accounts.