The Libretro Citra core documentation lists seven file extensions the core can load: .3ds, .3dsx, .elf, .axf, .cci, .cxi, and .app. A file with one of these extensions is a candidate, not a guarantee. Whether it actually runs depends on whether its contents are encrypted, whether the game needs extra files, and whether that specific title is known to work.
The extensions the Libretro Citra core can load
The Libretro documentation for Nintendo 3DS (Citra) is the primary reference for this list. It applies to the Libretro Citra core specifically, as documented when it was last checked on 8 October 2026. The seven listed extensions are:
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| Extension | Status in Libretro Citra core documentation |
|---|---|
.3ds |
Listed as loadable |
.3dsx |
Listed as loadable |
.elf |
Listed as loadable |
.axf |
Listed as loadable |
.cci |
Listed as loadable |
.cxi |
Listed as loadable |
.app |
Listed as loadable |
The list is a statement about what the core accepts by extension. It does not confirm that a given file is valid, decrypted, or compatible with a particular game. Standalone Citra builds and other frontends are not covered by this list, and their handling of these extensions is not established by the same documentation.
Encrypted games need AES keys
The same Libretro page states that encrypted games require AES keys. A supported extension therefore tells you nothing about whether a file’s contents are encrypted. A file can have a recognized suffix and still fail to load if the core lacks the keys it needs. Check the core’s documentation for how to supply AES keys in your setup, since the documentation consulted here does not describe the configuration steps.
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Some games need files dumped from a 3DS
The archived Citra compatibility list, preserved by the Azahar Emulator team and dated March 4, 2024, states that some games require additional files dumped from a 3DS and integrated into Citra. A game file alone may not be enough for these titles. The archived page does not list which games need extra files in the excerpt consulted, so check the compatibility entry for your specific game. The archived Citra compatibility list is the reference for that check.
File support and game compatibility are separate checks
Readers often treat “the emulator accepts this extension” and “this game works” as one question. They are two. When you are comparing a candidate file, check these four points in order:
- Whether the extension appears in the documentation for your exact core or frontend.
- Whether the game content is encrypted, and if so whether AES keys are configured.
- Whether the title needs additional system files dumped from a 3DS.
- Whether the particular game is listed as compatible in the compatibility list.
Failing any one of these can stop a game from loading even when the file type is correct.
CIA packages
The Libretro list does not include .cia. That absence does not prove that no Citra build can install or open CIA packages. The sources consulted do not establish whether standalone Citra accepts CIA files directly, or how that behavior differs between builds and operating systems. Confirm the handling of CIA files in the documentation for the exact build and frontend you use, and do not assume that “loading a game file” and “installing a package” work the same way.
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Troubleshooting a file that will not load
- Confirm the file’s extension is one of the seven listed for the Libretro Citra core. If it is
.cia, follow the CIA guidance above rather than treating it as a standard game file. - Check whether the game is encrypted. If it is, confirm the core has the AES keys it requires.
- Check whether the title needs additional files dumped from a 3DS. If it does, those files must be integrated into Citra before the game can run.
- Look up the game in the archived compatibility list. Note that the archive reflects the March 4, 2024 snapshot and may not match the behavior of current builds.
- If the game is listed but still fails, consult the compatibility list’s FAQ, which the archived page directs readers to for listed games that have trouble.
Working through these checks in order separates a format problem from an encryption problem, a missing-file problem, and a compatibility problem, which is usually the fastest way to find the cause.
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