Fission

Fission

Developer(s)	Microsoft
Latest version	Patch-based
Active	No
Platform(s)	Xbox One Xbox Series X/S Windows 11
Emulates	Xbox Xbox 360 (One & Series only)
License	Proprietary

Codename Fission is the official Xbox and Xbox 360 emulator made by Microsoft to allow for backwards compatibility on the Xbox One, Xbox Series X/S and for Windows 11 PCs. Microsoft stopped supporting its development in 2021, but the emulator itself it still entirely usable with supported games.

Overview

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. It supports 632 Xbox 360 games and 63 original Xbox games.

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.

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.

In July 2026, Microsoft ported Fission for Windows 11 PCs, albeit being limited just for original Xbox titles. It features more customizable options than its "console" counterparts. These games can also be played on non-Xbox devices through Xbox Game Pass Ultimate tier, which is powered by cloud technology. In less than a day, it was revealed that there is code for Xbox 360 emulation in the PC version of Fission, although it is currently unused, as there was no games from the system that were been re-released by Microsoft yet.