How to Adjust Screen Brightness on Windows, Mac, and Linux

The fastest way depends on your operating system and hardware

On Windows, use the keyboard shortcut Windows key + A to open the Quick Settings panel, then drag the brightness slider. On Mac, press F1 to dim or F2 to brighten, or open System Settings > Displays and adjust the slider. On Linux, the method varies by desktop environment — GNOME uses the system menu in the top-right corner, while KDE Plasma uses the system tray. If keyboard shortcuts do not work, your monitor may have physical buttons on the bezel that control brightness independently of your operating system.

Some laptops and external monitors also respond to brightness controls in their own software or settings menus. If you are using an external display connected via HDMI, DisplayPort, or USB-C, check whether the monitor manufacturer provides a control app or whether Windows and Mac detect the monitor as a smart display that responds to system brightness commands.

Key Takeaways

Windows brightness is fastest through Quick Settings (Windows key + A), while Mac uses F1 and F2 keys or the Displays settings panel.
Most monitors have physical buttons on the front bezel that control brightness independently of your computer's operating system.
Laptop brightness usually responds to keyboard shortcuts, but external monitors may require their own control software or physical buttons.
If system brightness controls do not affect your external monitor, check the monitor's manual or manufacturer website for a dedicated app.

Windows brightness controls

The quickest method on Windows 10 and Windows 11 is the Quick Settings panel. Press Windows key + A to open it, then drag the brightness slider left to dim or right to brighten. This works on most laptops and some external monitors that support DDC-CI (a standard that lets your computer communicate with the monitor).

If Quick Settings does not appear or the slider is missing, go to Settings > System > Display and scroll down to find the brightness slider. This method works on all Windows machines but takes slightly longer. Some laptops also have dedicated brightness keys on the keyboard — usually marked with a sun icon — that work without opening any menu. These physical keys often respond faster than software controls because they bypass the operating system.

If you have an older external monitor or one that does not support DDC-CI, the Windows brightness slider will not affect it. In that case, look for physical buttons on the monitor itself, usually on the bottom bezel or the right side. Consult the monitor's manual if the buttons are not obvious.

Mac brightness controls

On a Mac, the easiest method is the keyboard. Press F1 to dim the screen or F2 to brighten it. These keys work on all Macs with a built-in display and on many external monitors that support DDC-CI. If your keyboard does not have F1 and F2 (for example, on newer MacBook Pro models with Touch Bar), hold the fn key and press the brightness control icons on the Touch Bar.

For more precise control, open System Settings, click Displays, and drag the brightness slider. This method also shows you the current brightness percentage and lets you set it to a specific level. Some Macs also support automatic brightness adjustment — a toggle in the same Displays panel that dims the screen in low light and brightens it in bright environments.

External monitors connected to a Mac may not respond to the F1 and F2 keys or the system brightness slider. Check the monitor's manual or the manufacturer's website for a control app. Some newer monitors from brands like LG and Dell include apps that let you adjust brightness from your Mac, even if the monitor does not support DDC-CI.

Linux brightness controls

On GNOME (the default desktop on Ubuntu and Fedora), click the system menu in the top-right corner and look for a brightness slider. It usually appears near the volume control. Drag it to adjust brightness. If the slider does not appear, your monitor may not support DDC-CI or your graphics driver may not be fully configured.

On KDE Plasma (used by Kubuntu and other distributions), click the system tray in the bottom-right corner and find the brightness slider in the quick settings. Some KDE systems also respond to keyboard shortcuts like Fn + F5 and Fn + F6, depending on your laptop model and keyboard layout.

If the graphical controls do not work, you can adjust brightness from the command line using xrandr (for X11 displays) or brightnessctl (a tool that works across most Linux systems). Open a terminal and type brightnessctl set 50% to set brightness to 50 percent. This method requires some technical knowledge but works on almost any Linux setup.

Physical monitor buttons and on-screen menus

Most external monitors have physical buttons on the bezel — usually on the bottom edge or the right side — that control brightness without any software. Press the button marked with a sun icon or a plus sign to brighten, or the minus sign to dim. These buttons work regardless of your operating system or whether the monitor is connected via HDMI, DisplayPort, or USB-C.

Some monitors also have an on-screen menu (OSD) that appears when you press a button on the bezel. Navigate to the brightness or backlight option using the arrow buttons, then adjust it with the plus and minus buttons. The exact location of these controls varies by manufacturer — check the monitor's manual if the buttons are not labeled clearly.

Physical buttons are often more reliable than software controls because they do not depend on your computer recognizing the monitor or having the right drivers installed. If your monitor is very old or uses an unusual connection type, the physical buttons may be your only option.

Troubleshooting when brightness controls do not work

If the keyboard shortcuts or system settings do not change your screen brightness, first check whether you are trying to control an external monitor or a laptop display. Laptop brightness usually responds to system controls, while external monitors often require physical buttons or dedicated software.

On Windows, make sure your graphics driver is up to date. Open Device Manager, expand Display adapters, right-click your graphics card, and select Update driver. Outdated drivers sometimes prevent Windows from communicating with external monitors. On Mac, brightness controls usually work out of the box, but restarting your computer can fix connection issues with external displays.

If an external monitor has a brightness slider in Windows or Mac settings but it does not actually change the screen, the monitor may not support DDC-CI. Check the monitor's manual or the manufacturer's website to confirm. Some monitors require you to enable DDC-CI in their on-screen menu before the computer can control brightness remotely.

When to use automatic brightness

Both Windows and Mac offer automatic brightness adjustment, which uses a light sensor to dim the screen in dark rooms and brighten it in bright environments. This can reduce eye strain and save battery power on laptops. On Windows, go to Settings > System > Display and toggle Adaptive brightness on. On Mac, open System Settings > Displays and check Automatically adjust brightness.

Automatic brightness works best if you spend time in different lighting conditions throughout the day. If you work in a consistent environment or prefer full control over your screen, you can leave it off and adjust brightness manually. Some people find automatic adjustment distracting, especially if the light sensor is sensitive and the screen flickers when lighting changes.

Frequently Asked Questions

Why does my brightness slider not affect my external monitor?

External monitors often do not support DDC-CI, the standard that lets your computer control brightness remotely. Check the monitor's manual to confirm support. If it does not have DDC-CI, use the physical buttons on the monitor bezel instead. Some monitors require you to enable DDC-CI in their on-screen menu before it works.

Can I adjust brightness on a monitor connected via HDMI?

Yes, if the monitor supports DDC-CI. The connection type (HDMI, DisplayPort, USB-C) does not matter — what matters is whether the monitor supports the standard. Try the system brightness controls first. If they do not work, use the physical buttons on the monitor or check the manufacturer's website for a control app.

What if my laptop keyboard does not have brightness keys?

Use the system settings instead. On Windows, press Windows key + A and drag the brightness slider. On Mac, press F1 and F2, or open System Settings > Displays. Some newer laptops use touch-sensitive controls or function keys that require holding the fn key.

Does adjusting brightness save battery power?

Yes, lowering brightness reduces power consumption on laptops and can extend battery life by 10 to 20 percent depending on how much you lower it. The display is usually one of the biggest power consumers on a laptop, so dimming it has a noticeable effect. Enabling automatic brightness adjustment can help optimize battery life without requiring manual adjustment.

Can I set different brightness levels for different apps?

No, brightness is a system-wide setting that affects your entire screen. Some apps let you adjust their own contrast or background color (for example, enabling dark mode), but that is different from monitor brightness. If you need different brightness levels for different tasks, you will have to adjust the system brightness manually when you switch between them.

This guide is for general information only and is not medical, financial, legal, or other professional advice. For decisions specific to your situation, consult a qualified professional. See our Editorial Policy.