Press the F5 key to decrease keyboard backlight until it turns off
Use the Control Center in the menu bar
Open Control Center
Click Keyboard Brightness
Drag the slider all the way down
Go to System Settings
Click Keyboard
Turn off Adjust keyboard brightness in low light if available
On MacBook Pro with Touch Bar, use the keyboard brightness controls in Control Center or the Function row
If your Mac has an ambient light sensor, cover the sensor briefly to test automatic backlight behavior