Wii U ROMs work by using an emulator to mimic the functionality of the Wii U console. The emulator reads the ROM file, which contains the game's data, and translates it into a format that can be played on a computer or other device. This allows gamers to play Wii U games on devices other than the original console, often with improved performance and graphics.

The Nintendo Wii U was, by traditional sales metrics, a commercial failure. Sandwiched between the explosive success of the Wii and the hybrid phenomenon of the Switch, the Wii U sold barely over 13 million units. Yet, for those who owned one, the console was a treasure trove of hidden gems—from Super Mario 3D World to Xenoblade Chronicles X and The Legend of Zelda: Breath of the Wild (the definitive version before the Switch port).

The most popular format for modern emulation and homebrew is the decrypted folder structure, often referred to as the "Loadiine format" or "NUS format" (Nintendo Update Server). Instead of a single massive file, the game is broken down into three distinct folders: