If your MacBook screen is stuck too dim (or too bright) and the brightness keys, slider, or auto-brightness will not respond, it is almost always a setting or a stuck sensor — not a broken screen. Work through these fixes in order and stop as soon as one works.
First: which problem do you actually have?
- Keys do nothing: F1/F2 (or the brightness keys on the Touch Bar) do not change anything → jump to fix 2 and 3.
- Screen dims by itself: brightness drops when you are not touching it → that is auto-brightness or Low Power Mode (fix 1).
- Slider is grayed out: the Displays slider will not move → fix 4 and 5.
- Whole screen is nearly black but you can faintly see it under a flashlight → that is a backlight/hardware issue, skip to the hardware section.
1. Turn off automatic brightness
The most common cause of "my brightness changes on its own" is the ambient light sensor. Go to System Settings > Displays and turn off Automatically adjust brightness. On older macOS it lives under System Preferences > Displays. Also check Battery > Low Power Mode — Low Power Mode intentionally dims the screen; set it to Never (or Only on Battery) while you test.
2. Make sure a dark cover, sensor, or Night Shift is not fooling it
The ambient sensor sits near the camera at the top of the screen. A case flap, sticker, or even a shadow can trick it into dimming. Uncover it and wave your hand away. Then rule out color shifts: System Settings > Displays — toggle Night Shift and True Tone off to confirm the screen is not just looking dim or warm. If that fixes the look, see our guide on Night Shift and True Tone.
3. Fix brightness keys that do nothing
If F1/F2 do not change brightness:
- Try the on-screen slider instead (Control Center > Display in the menu bar). If the slider works but the keys do not, it is a keyboard-function setting.
- Go to System Settings > Keyboard > Keyboard Shortcuts > Function Keys and make sure "Use F1, F2, etc. keys as standard function keys" is off (when it is on, you must hold fn + F1/F2 to change brightness).
- On a Touch Bar MacBook Pro, the brightness control may be collapsed — tap the arrow to expand the Control Strip.
4. Restart the display service (grayed-out slider)
If the Displays brightness slider is completely grayed out, the display service has usually hung. Restart the Mac fully (do not just close the lid). If that does not restore it, the graphics or logic board may be dropping the panel — continue to fix 6 and the hardware section.
5. Reset the display firmware (SMC / settings)
On Apple Silicon Macs (M1, M2, M3), there is no SMC reset — a full shutdown for 30 seconds and restart does the same job. On Intel MacBooks, reset the SMC (which controls the backlight): shut down, hold Shift-Control-Option + power for 10 seconds, release, then power on. This fixes a surprising number of stuck-brightness cases on Intel machines.
6. Update macOS
Brightness and auto-brightness bugs are a common target of macOS point updates. Go to System Settings > General > Software Update and install anything pending, then re-test.
External monitor brightness will not change
macOS cannot always control an external display’s brightness — many monitors only respond to their own physical buttons. If the MacBook’s built-in screen adjusts but the external one does not, that is normal; use the monitor’s buttons or a utility like the display’s own menu. If the external screen is also flickering, see MacBook screen flickering fixes.
When it is hardware, not a setting
If none of the above works and the screen is very dark even at "full" brightness — especially if you can only see the image under a bright flashlight — the backlight or display cable has likely failed. On 2016–2018 13-inch MacBook Pros this is often flexgate (stage-light or dead backlight). We break down repair-vs-replace math in MacBook flexgate: repair it or sell it?
A dead-backlight repair often costs more than the machine is worth. If yours is out of warranty, it is frequently cheaper to move to a known-good refurbished Mac. A refurbished MacBook Air M1 starts at $569.99 and the 14-inch MacBook Pro M1 Pro from $899.99 — both with a bright, healthy display and our one-year warranty. You can also browse current Apple clearance deals for the lowest prices.
Not worth fixing? We buy broken and dim-screen MacBooks. Get a fast quote on our broken MacBook trade-in page and put the credit toward an upgrade.
FAQ
Why does my MacBook screen keep dimming on its own?
Almost always automatic brightness (the ambient light sensor) or Low Power Mode. Turn off "Automatically adjust brightness" in Displays and set Low Power Mode to Never while you test.
Why do my brightness keys not work?
Either the function-key setting is forcing you to hold fn, or the display service has hung. Check Keyboard > Function Keys, then restart. If the on-screen slider works but the keys do not, it is a keyboard setting, not the screen.
How do I reset brightness settings on a Mac?
On Apple Silicon, shut down fully for 30 seconds and restart. On Intel, reset the SMC (Shift-Control-Option + power for 10 seconds while off). This clears most stuck-brightness states.
My brightness slider is grayed out — is my screen broken?
Not necessarily. A grayed-out slider usually means the display service hung and a full restart restores it. If it stays grayed out and the screen is very dark, it points to a backlight or logic-board fault.