NotProton enables the Steam Play experience from Linux Steam in the macOS Steam client.

This is done by forcibly enabling the Steam Play functionality in macOS Steam (which is present and inert) as well as by porting some components of Valve's Proton to macOS.

This tool is intended to be used with Steam Client 1788652215 or 1790121765 and CrossOver Preview 2026082. Both the FEX build and the Rosetta build are supported. The Rosetta build is the recommended version, as the FEX one is an early state.

The macOS app itself is located in the app folder. The core logic is in dylib. lsteamclient is a macOS port of Valve's lsteamclient. steam-shimis a port of Valve's steam-helper from Proton 9. ntdll-patch patches the copy of CrossOver that the app makes/places in the ~/Library/Application Support/notproton/runners/ folder so that lsteamclient is loaded.

This release is coming several days past when I wanted to release it, so the documentation is quite sparse. Sorry about that, I'll improve it over the next day or two.

Please read NOTICE for license information.

Please open issue reports with any issues. PRs are welcome and encouraged.