Understanding the transfer process
While the system transfer process itself is very simple, there are a few important details to be aware of.
The length of time it takes to transfer content from a Wii console to a Wii U console varies depending on the volume of data being moved across. Please do not turn off the power to the Wii U console during the transfer process, or remove the SD Card unless instructed to do so.
Transferred content will be removed from the Wii console during the transfer process, and cannot be transferred back onto Wii after the process is finished. Transferred software cannot be re-downloaded onto the Wii console.
It is not possible to specify which data will be transferred.
If there is content on the Wii U console that is also present on the Wii console, the Wii U content will be deleted and overwritten by the Wii content.
It is possible to transfer the content from multiple Wii consoles to a single Wii U console. Each Wii requires an individual system transfer. Please bear in mind the point above.
If there are Wii Points on both the Wii console and Wii U console, these two accounts will be merged. A system transfer is not possible if the total account balance would exceed 10,000 Wii Points.