Chosen Solution
When I’m at school the keyboard light on my MacBook Air turns off and won’t let me turn it back on; it shows the x symbol. It doesn’t just happen to me, it happens to some of my friends as well. Why is that? I’m just curious.
So on the macbook air, there is an ambient light sensor (Photo detector). when the room is bright you can see the keys, so the backlight is not needed and turned off to save power. when its dark, it turns on so you can see the keyboard. you can also manually change it by pressing these keys:
typically, (at least for my macbook air and laptops I’ve seen) its somewhere in the red box.
If you cover it with your finger, you should see the screen brightness go lower and the keyboard up. What is a Photodetector?
Apple has documented this feature on their website: Adjust the brightness of your backlit keyboard https://support.apple.com/kb/HT202310 If you can’t adjust your keyboard’s brightness manually, it’s likely because you’re in a very bright environment and you have your Mac set to automatically adjust the brightness. In this case, the backlit keyboard turns off. When you move to a location with less light, you can once again adjust the keyboard’s brightness.
