Microsoft has developed a Copilot OS prototype it calls by the codename 'Ion.'

Its existence was confirmed after 2024 materials were leaked, Windows Central reported on Thursday.

According to the report, Ion is a web technology-based interface that uses the Microsoft Edge browser. It offers desktop-style functions such as a Start menu, taskbar and window layering. It runs by replacing the desktop shell on top of Windows 11, or it also works on AOSP Android.

Leaked documents also mentioned a separate compatible OS called 'Win3.' Windows Central reported that it would be a lightweight version of Windows that reduces legacy code to improve boot speed, battery life and security, but would not support existing apps.

Ion runs only web apps and websites. When existing Windows apps are needed, it provides them through a cloud PC by linking with Windows 365.

Copilot sits at the center of the interface. The Start menu uses a Copilot icon instead of the Windows icon. Users handle starting tasks, browsing the web, searching files, AI chat and launching web apps at once through a multimodal omnibox.

It is unclear whether Project Ion will actually be released. Microsoft recently announced an agent-type OS, 'Project Solara,' based on Windows and Android codebases.