Windows 11 in S mode is a version of Windows 11 that is designed for security and performance, while providing a familiar Windows experience. It is available only in the Windows 11 Home edition. S mode is much more energy-efficient than standard Windows because it runs fewer background processes and services, which can burn energy. The main feature of S mode is that it only allows apps from the Microsoft Store to be installed, ensuring that all apps are secure and up-to-date. This mode takes advantage of the built-in security capabilities of Windows 11, such as Windows Defender and Windows Hello, to provide users with an extra layer of protection. If you want to install an app that isnt available in the Microsoft Store, youll need to switch out of S mode. Switching out of S mode is one-way, and if you make the switch, you wont be able to go back to Windows 11 in S mode. To switch out of S mode, you need to go to Settings > System > Activation, and in the Switch to Windows 11 Pro section, select Go to the Store. It is important to note that switching out of S mode is free of charge.