It's easy — once you know how. To adjust the brightness of a backlit keyboard on a Chromebook you need to press the Alt key and tap the screen brightness up/screen brightness down keys. This will increase/decrease the intensity of your keyboard backlight.Aug 8, 2021
How do I know if my Chromebook has a backlit keyboard?
Since most Chromebooks don't have a dedicated backlight key, you'll need to use Alt with the regular screen dimming key. Press the screen brightness key. You can usually find this key above the 7, 8, and 9 keys. It looks like a large circle and the key to make the brightness dimmer looks like a smaller circle.