If you own a physical Wii U, you can modify it using custom firmware (like Aroma or Tiramisu) to run backups directly from an SD card or external USB hard drive.
A compressed format that saves space while maintaining functionality, often preferred for emulation.
A (or more accurately for disc-based systems, an ISO or WUX/WUD file) is a digital copy of the game's data extracted from a physical Wii U retail disc. For the Wii U, these files generally come in three formats:
Unpacked game files. Highly accessible for modding and asset editing, but less organized than single files. .app , .h3 files inside a folder Modded Wii U Consoles