Stop your Mac screen changing brightness by itself

Why it happens

Your Mac has a small light sensor near the camera. With automatic brightness on, it brightens the screen in a sunny room and dims it in a dark one, and even a hand or a passing shadow can set it off. Separate battery settings can also dim the screen when you unplug.

How to fix it

1. Click the Apple menu, choose System Settings and click Displays. If you have more than one screen, click your Mac's built-in display at the top.

2. Turn Automatically adjust brightness off.

   Displays›Automatically adjust brightness

3. Drag the Brightness slider to a level that feels right. It will now stay there.

   Displays›Brightness

Still not fixed?

1. If the screen dims only when you unplug a MacBook, open Battery, click Options… and turn off Slightly dim the display on battery.

   Battery›Options…›Slightly dim the display on battery

2. Low Power Mode lowers brightness to save energy. In Battery, set Low Power Mode to Never. If you see Energy Mode instead, choose Automatic in the On battery and On power adapter pop-ups.

   Battery›Low Power Mode

3. A screen that dims after you stop using it for a minute is getting ready to turn off. Choose longer times for Turn display off on battery when inactive and the power adapter option in Lock Screen.

   Lock Screen

4. If you don't see Automatically adjust brightness, your screen has no light sensor. External monitors usually change brightness with their own buttons.

5. Still flickering or jumping with all of these off? That points to the display or its sensor. Contact Apple Support or book an Apple repair.