If you're diving into PC gaming with the Wii U emulator Cemu , you'll quickly encounter mentions of "keys." Unlike traditional ROMs for older consoles, Wii U games are encrypted, and keys are the essential tools needed to unlock them. What Are Cemu Keys? Keys in Cemu are small pieces of cryptographic data that decrypt your legally obtained Wii U game files (typically in WUA, WUD, or WUX format). Without the correct keys, Cemu will see your game files as garbled, unreadable data.