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Developer(s) Microsoft
Latest version Patch based
Active No
Platform(s) Xbox One
Xbox Series X/S
Emulates Xbox
Xbox 360

Codename Fission is the official Xbox and Xbox 360 emulator made by Microsoft to allow for backwards compatibility on the Xbox One and Xbox Series X/S.

However with November 2021 update Microsoft ends the program and said: "This latest and final addition of 70+ titles to the backwards compatibility program was only possible through the passion and feedback from the community," Microsoft said. "Your constant requests for specific titles and enhancements encouraged the Backwards Compatibility team to partner with the original creators to preserve thousands of games from over four generations of Xbox. While we continue to stay focused on preserving and enhancing the art form of games, we have reached the limit of our ability to bring new games to the catalog from the past due to licensing, legal and technical constraints. Thank you for being part of this journey with us."[1]


Its development was announced in June 2015 and the first batch of games were released on November 12. It was originally released as an Xbox 360 only emulator, but original Xbox emulation was later added in 2017 due to popular demand. The last batch of games were added to the emulator on November 15, 2021, due to licensing and technical issues.[2]. It supports 632 Xbox 360 games and 63 original Xbox games[3].

Most backwards compatible games can be purchased and downloaded through the Microsoft store, or inserted via the disc drive. Unlike the previous Fusion emulator for the 360, games do not run directly from the disc, and the Xbox One or Series X/S must be connected to the internet for DRM purposes. When a disc is inserted, a prompt saying an update is required to start the game will appear, accepting the prompt will download a repackaged version of the game to fit the Xbox One or Series X/S format.

Several original Xbox and Xbox 360 games are enhanced for the Xbox One X. The enhancements include improved graphics, new visual effects, higher framerates, and upgraded resolutions up to 4K[4][5].

Two select original Xbox games do not download as the original versions when their discs are inserted. Battlefield 2: Modern Combat and Grand Theft Auto: San Andreas will instead download as the 360 versions of these games.

The emulator has actually been dumped from the Xbox One's OS, see this page.