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Cemu does not use one file type. It works with several Wii U game formats and layouts, and which one applies depends on how your game data is packaged. The main options are a WUA archive, a WUD or WUX disc image, a Loadiine folder that contains an RPX executable, and, according to Cemu’s release history, NUS-style .app titles and .wuhb homebrew bundles.
The short answer: several formats, grouped by how they are packaged
Cemu is a Wii U emulator, and the project’s official repository says it can run most Wii U games and homebrew in a playable state. The Cemu Project repository lists Windows, Linux, and macOS as platforms, and it warns that the native macOS build is currently experimental and not stable enough for issue-free gameplay. Because Cemu is a platform for running game data rather than a source of it, the useful question is not “which single extension” but “which packaging does my existing data use.”
The formats fall into two practical groups. Single-file formats are archives and disc images. Folder layouts keep the game’s internal files separate. Separately, each format is either encrypted or decrypted, and that distinction determines whether you need a key file.
Supported formats at a glance
| Format or layout | Packaging | Encryption status | What the sources establish |
|---|---|---|---|
.wua |
Single-file archive | Decrypted | Identified as a Cemu ROM format in the EmuDeck Cemu setup guide, which is third-party guidance. |
.wud |
Single-file disc image | Encrypted | Title reads are mentioned in Cemu release notes; the EmuDeck guide groups it with encrypted formats. |
.wux |
Compressed disc image | Encrypted | Title reads are referenced in Cemu release history; the EmuDeck guide groups it with encrypted formats. |
| Loadiine folder | Folder with code, content, and meta subfolders |
Decrypted | Described in the EmuDeck guide, which also lists .rpx as a supported parser type. |
.rpx |
Executable inside a Loadiine-style folder | Not applicable as a standalone game | Not a complete game by itself; the surrounding folder holds the rest of the data. |
.app |
NUS title content | Not stated | Support was added in Cemu 2.1, according to the Cemu release notes. |
.wuhb |
Wii U homebrew bundle | Not stated | Support was added in Cemu 2.1, according to the Cemu release notes. |
Single-file formats
WUA archives
A WUA is a single-file Wii U archive. The EmuDeck Cemu guide classes it as a decrypted format, which means the setup guide does not require a key file for it. It is the simplest single-file option to describe, though the guide is a practical walkthrough and not a full specification of the file’s internal structure.
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WUD and WUX disc images
WUD and WUX are disc-image formats. WUD is an uncompressed disc image, and WUX is a compressed one. Both are grouped with encrypted formats in the EmuDeck guide, and encrypted ROMs need the correct keys.txt file for Cemu to read them. If you have a disc image in either format, a missing or mismatched key file is the most likely reason it fails to load, so check that first before assuming the image itself is damaged.
Folder layout: Loadiine and RPX
A Loadiine folder is a decrypted, extracted game. The EmuDeck guide describes three subfolders:
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code, which holds the executable files, including the.rpxfile that Cemu’s parser recognizescontent, which holds the game’s data filesmeta, which holds metadata about the title
The practical rule is that you point Cemu at the folder, not at the RPX inside it. An RPX file on its own does not contain a complete game, so a lone executable without the surrounding content and meta folders will not work as a full title.
Encrypted versus decrypted: what changes for setup
The main setup difference is the key file. Encrypted formats such as WUD and WUX require a matching keys.txt. Decrypted formats such as WUA and Loadiine folders do not, according to the EmuDeck guide. That guide recommends decrypted formats for a straightforward setup. This is a recommendation from a third-party setup guide, not an official Cemu requirement, so you can use an encrypted image if that is what you have.
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Base game versus updates and DLC
Cemu’s sources do not establish how updates or DLC content should be combined with a base game across the formats above. Treat that as an open question for your specific title and check the setup documentation for the format you are using before assuming an update will load automatically.
Which format fits what you already have
- A single archive: a WUA file is supported and does not need a key file.
- A disc image: a WUD or WUX file is supported, but it needs a valid
keys.txt. - An extracted game folder: a Loadiine layout with
code,content, andmetasubfolders is supported; point Cemu at the folder. - A homebrew bundle or NUS content:
.wuhband.appsupport was added in Cemu 2.1, per the release notes; check the release page for the version you run.
No format is universally best. The choice depends on which packaging your data already uses, and the sources here are about compatibility rather than quality or performance. For the current build and platform notes, see the Cemu release history.
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Platform caveat
File format support does not guarantee that a title will be playable. Cemu’s own repository describes most games as playable rather than all games, and the native macOS build is experimental.
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