Your Mac automatically adjusts its display brightness to ensure a comfortable screen experience regardless of the lighting environment.
However, you might have encountered situations where your Mac’s screen dims or brightens out seemingly at random. Not only can it be annoying, but it can also strain your eyes and make it difficult to focus on your work.
In this guide, we will go over practical solutions to prevent your iMac, MacBook Air, MacBook Pro, or the external Apple Studio Display from dimming the screen brightness or increasing it randomly.
Wait a short while for the screen to warm up
After you boot up your Mac, its display may take a while to warm up and slowly reach full brightness. So, immediately after turning on your Mac, it’s normal to see a gradual increase or shift in screen brightness for a short while.
Clean the ambient light sensor area
This is the most important solution if your MacBook Air or MacBook Pro is randomly changing the screen brightness without you touching the brightness key or modifying the light in your room!
Like iPhone, iPad, and most other smartphones, your Mac laptop, iMac, and Studio Display have an ambient light sensor, which adjusts the display brightness based on the light in your environment.
Here’s the location of ambient light sensors on Mac:
- MacBook, MacBook Air, MacBook Pro, and old iMacs: Near the top FaceTime web camera
- New iMac with Apple silicon and Apple Studio Display: Top left bezel area of the screen (See video)
Since the ambient light sensor is in the middle of the top bezel of the MacBook, body oils and dust from your finger may smudge this sensor when you open and close the lid. This regularly causes the ambient light sensor to work improperly, as it can’t gather the light information correctly due to the layer of dirt blocking it.
To address this, wipe the ambient light sensor area using a soft cloth, and your Mac will undoubtedly stop changing the screen brightness automatically/randomly.
Remove the tape, cover, or webcam
If you have put a piece of tape or a cover over the camera for privacy or mounted a webcam to your Mac that partially blocks the ambient light sensor, then remove it to prevent your Mac from changing the brightness irregularly.
Restart your Mac
It’s also possible that screen brightness is malfunctioning due to temporary glitches, and the quickest way to fix this is by restarting your Mac from the Apple menu  > Restart.
Turn off automatic screen brightness
Disabling auto-screen brightness can ensure a uniform experience if your work, like video editing or image color correction, involves using the screen at a fixed brightness. It can also help if you’re constantly annoyed by your Mac adjusting the screen brightness to a level it thinks is best.
Here’s how to disable automatic screen brightness on Mac:
- Click the Apple icon  and choose System Settings.
- Select Displays.
- Turn off the switch for ‘Automatically adjust brightness.’
On macOS Monterey and earlier: Go to System Preferences > Displays and uncheck the box for Automatically adjust brightness.
Note: You won’t see the option to automatically adjust the brightness if your Mac doesn’t have an ambient light sensor. Mac mini, Mac Studio, and Mac Pro fall into this category unless they are connected to a compatible monitor like the Apple Studio Display.
Play around with True Tone
True Tone automatically makes the screen a bit warmer or cooler based on your lighting condition. Now, this should not affect the brightness, but the shift in display colors may give the impression that your screen is changing. So, go to System Settings > Displays and see if you prefer the display with True Tone enabled or disabled.
Note: True Tone and HDR aren’t available on all Macs.
Turn off HDR
Your Mac can automatically adjust the display when it’s connected to an HDR display, and you view HDR content. This can cause a change in brightness as showing HDR content in the best quality has a certain brightness level requirement. However, if you would prefer your display to not change its appearance, go to System Settings > Displays and turn off High Dynamic Range.
Stop your MacBook from lowering screen brightness on battery
When you remove your Mac notebook from charging, its brightness is dimmed slightly to save battery, but if it hinders your workflow, you can quickly stop your MacBook from doing that.
Turn off Mac’s Low Power Mode
To extend the battery backup, your MacBook reduces the screen brightness when it’s in Low Power Mode. But if it leads to random display problems, you can turn off Low Power Mode from System Settings > Battery.
Quit or uninstall third-party brightness apps
Some people use third-party apps like Lunar or ExternalDisplayBrightness to control Mac’s built-in or connected monitor brightness. If you’re also using one and facing brightness issues, consider quitting or uninstalling these apps.
In case the problem gets fixed, you can be sure that it was caused by these apps.
Are you using an iPad or Mac as a second display?
You may momentarily notice a slight shift in screen brightness when you connect or disconnect your iPad or another Mac as the second display. It’s normal.
Still, you can go to System Settings > Displays > select your main display and make sure that your main screen’s Color profile is the standard one or the one you had set earlier. Usually, it’s your monitor’s name or Color LCD.
Turn off Night Shift
Night Shift filters blue light from the display. If you use it on your Mac, go to System Settings > Displays > Night Shift and turn it off.
Update your Mac and Studio Display
Update your Mac if it is running an outdated version of macOS
- On macOS Ventura and later: System Settings > General > Software Update.
- On macOS Monterey and earlier: System Preferences > Software Update.
Apple Studio Display and Pro Display XDR also receive updates. So, make sure it’s on the latest firmware.
Disconnect the Studio Display and reconnect it
If you’re facing brightness issues on Apple’s Studio Display, disconnect it from your Mac and connect it again. While at it, ensure the Thunderbolt cable isn’t damaged.
Reset NVRAM
Macs with an Intel processor have an additional tiny memory called NVRAM or PRAM, which stores quick system settings like startup-disk selection, time zone, display resolution, sound settings, etc. If your Mac’s display is not working perfectly, reset its NVRAM.
Note: This doesn’t apply if your Mac has an Apple silicon (M1, M2, or its successors).
Related: How to know if your Mac has Apple silicon or Intel processor
Reset SMC
Resetting the System Management Controller (SMC) is one of the last resorts to fix power-related issues on Macs with an Intel processor. So, if your Intel Mac’s display is misbehaving, go ahead and reset its SMC. If you have a Mac with Apple silicon, simply turn off your computer and turn it back on.
Reinstall macOS
In case nothing helps, reinstall macOS without deleting your data, and it should solve the irritating screen brightness problem.
Finally, if you can’t fix the problem, contact Apple Support and set up a repair request at your nearest Apple Service Center for hardware inspection of your Mac or Studio Display.
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