Key'n'Stroke is described as 'displays keystrokes in an overlay window. (Windows 8+)'. There are eight alternatives to Key'n'Stroke for Windows and Linux. The best alternative is Carnac, which is both free and Open Source. Other great apps like Key'n'Stroke are PointerFocus (Paid), Pen Attention (Free), SpotOnTheMouse (Freemium) and PainterMouse (Free Personal).
SpotOnTheMouse is a mouse pointer and keyboard action visualization software. It makes mouse clicks visible ,it improves the perceptibility of the mouse pointer & it shows the special keys and combinations of keys pressed on the keyboard.