How to disable rounded corners in Windows 11?

Solution 1:

yes you can.. https://github.com/valinet/Win11DisableRoundedCorners/releases

doesn't work on start menu, but it works

Solution 2:

Windows 11 will revert to square corners if you turn off hardware graphics acceleration, which will unfortunately also turn off other visual features like transparency.

Another (unrecommended) option is to ... disable entirely your graphics hardware. In Device Manager, expand Display Adapters, right-click your display adapter and Select "Disable Device". The screen will flicker a moment but, when Windows returns, the rounded corners will be gone. But so may also be gone the video performance.