A WUD file is a disk image file dumped from a Wii U game disc. It contains information about a Wii U game that can be run by an emulator, such as Cemu, on a computer. WUD files are typically split into segments because of the large amount of information in a Wii U game.

WUD files are most often created using Homebrew for Wii U. A user dumps the the game information from the Wii U game to the WUD file. Since the game information is large in size (over 20 GB), multiple WUD files are created to store segments (around 2 GB) of the game. Therefore, the files must be merged into one WUD file before the game can be opened and played by an emulator. To open a WUD file in Cemu, select File → Load and choose the WUD file you want to open. You can compress a WUD file to save space on your computer using the Wii U image compression tool. Compressed WUD files become .WUX files.