The quickest way to change brightness

Most monitors have physical buttons on the front or side that control brightness directly. Look for a button labeled with a sun symbol, a plus and minus pair, or sometimes just marked "Menu." Press the button to open an on-screen menu, then use the arrow buttons to find brightness (often called "Brightness" or sometimes "Luminance"), and adjust it up or down.

If your monitor has no visible buttons, check the bottom bezel or the back panel — some monitors hide controls there. A few newer monitors use touch-sensitive areas instead of physical buttons, which work the same way but respond to your finger rather than a press.

The brightness adjustment you make on the monitor itself overrides anything your computer is set to, so this is the first place to check if your screen suddenly looks too dark or too bright.

Key Takeaways

  • Physical buttons on your monitor (usually marked with a sun symbol or plus/minus) are the fastest way to adjust brightness and work independently of your computer settings.
  • If your monitor has no buttons, look for a menu control on the back panel or check your monitor's manual to find where controls are located.
  • Windows and Mac both have brightness controls in their system settings, but these work only if your monitor supports DDC-CI communication with your computer.
  • Brightness and contrast are separate controls — brightness affects how dark or light the overall image is, while contrast affects the difference between light and dark areas.
  • If brightness controls do nothing, your monitor may not support computer-based brightness adjustment, and you will need to use the physical buttons instead.

Using Windows brightness controls

Windows 10 and 11 both have brightness sliders in the Quick Settings menu. On Windows 11, swipe in from the right edge of the screen or press Windows key + A, then look for the brightness slider near the top. Drag it left to darken or right to brighten.

On Windows 10, the same slider appears in the Action Center (bottom right corner, or Windows key + A). However, this control only works if your monitor supports DDC-CI, a communication standard that lets your computer talk to your monitor. Many older monitors and some budget monitors do not support it, in which case the slider will have no effect.

If the slider does nothing, your monitor likely does not support DDC-CI. Switch to using the physical buttons on your monitor instead. You can also check your monitor's manual or the manufacturer's website to confirm whether DDC-CI is supported.

Using Mac brightness controls

On a Mac, brightness is controlled through the menu bar at the top of the screen. Click the Control Center icon (usually in the top right), then look for the brightness slider. Drag it left to darken or right to brighten. On older Macs, you may see a dedicated brightness icon in the menu bar instead.

Like Windows, Mac brightness controls require your monitor to support DDC-CI. If you are using an external monitor and the slider does nothing, the monitor does not support this feature. Built-in Mac displays (on MacBooks and iMacs) always respond to the brightness control, but external third-party monitors may not.

If your external monitor does not respond, use its physical buttons instead. Some Mac users also use third-party apps like Lunar or MonitorControl to adjust external monitor brightness, but these are optional tools — the physical buttons on your monitor will always work.

Understanding brightness versus contrast

Brightness and contrast are two separate controls, and adjusting one does not change the other. Brightness controls how light or dark the entire image appears — turning it up makes everything lighter, turning it down makes everything darker. Think of it like dimming a light bulb.

Contrast controls the difference between the brightest and darkest parts of the image. High contrast makes blacks darker and whites brighter, creating a sharper-looking image. Low contrast makes the image look washed out or flat. Most people leave contrast at the factory setting (usually 50%), but if your image looks dull or too harsh, adjusting contrast can help.

If your screen looks too dark, start by raising brightness. If it looks washed out even after brightness is up, try raising contrast slightly. If it looks too harsh or has crushed blacks (dark areas with no detail), lower contrast a bit. Both controls are in your monitor's menu, accessed the same way as brightness.

Finding the right brightness for your space

The right brightness depends on your room's lighting. In a bright room with lots of natural light, you may need higher brightness to see the screen clearly. In a dim room or at night, high brightness can cause eye strain and make it harder to see details. A good starting point is to set brightness so the screen is noticeably brighter than the wall behind it, but not so bright that it looks like a light source.

If you spend long hours at your monitor, consider using your computer's built-in blue light filter or night mode in the evening. Windows calls this "Night Light," and Mac calls it "Night Shift." These reduce blue light in the evening, which can help reduce eye strain and sleep disruption. You can find these in your display settings and set them to turn on automatically at sunset.

Some monitors also have an eco mode or low-power mode that reduces brightness automatically. Check your monitor's menu to see if this option exists — it can save energy and reduce eye strain if you find the default brightness too high.

What to do if brightness controls are not working

If your monitor's physical buttons do nothing, the monitor may be in a locked state or the buttons may be broken. Some monitors have a physical lock switch that disables the buttons to prevent accidental changes. Check the back or side of your monitor for a small switch labeled "Lock" or similar, and make sure it is in the unlocked position.

If the buttons still do not work, try unplugging the monitor for 30 seconds and plugging it back in. This resets the monitor's internal controls and sometimes fixes unresponsive buttons. If that does not help, the buttons may be physically broken, and you will need to contact the monitor manufacturer or consider replacing the monitor.

If your computer's brightness slider does nothing but the monitor's physical buttons work fine, your monitor straightforward does not support DDC-CI. This is normal for many monitors — it just means you will always adjust brightness using the physical buttons instead of the computer's settings. This is not a problem; it just means one extra step when you want to change brightness.

Frequently Asked Questions

Why does my brightness slider in Windows or Mac not work?

Your monitor likely does not support DDC-CI, a communication standard that lets your computer control brightness. This is common on older monitors and budget models. Use your monitor's physical buttons instead — they work independently of your computer and will always function.

Is it bad to keep brightness very high all the time?

Very high brightness can cause eye strain, especially in dim rooms or at night. It also uses more power. Set brightness high enough to see clearly in your room's lighting, but not so high that the screen looks like a light source. In the evening, lower brightness or use your computer's night mode to reduce strain.

What is the difference between brightness and backlight?

Brightness is the overall lightness or darkness of the image. Backlight is the light source behind the screen that makes the image visible. On most monitors, adjusting brightness actually adjusts the backlight. The terms are often used interchangeably, and you do not need to worry about the distinction — just use the brightness control.

Can I adjust brightness separately for different windows or programs?

No. Brightness is a monitor-wide setting that affects everything displayed on that monitor. You cannot make one window brighter and another dimmer. However, some programs (like photo editing software) have their own contrast and brightness tools for the image you are working on, which is different from monitor brightness.

Why does my monitor brightness keep changing on its own?

Some monitors have an auto-brightness feature that adjusts brightness based on ambient light. Check your monitor's menu for an option called "Auto Brightness," "Adaptive Brightness," or "Eco Mode," and turn it off if you prefer manual control. On Windows, also check if Night Light is turning on automatically at sunset, which can make the screen appear dimmer in the evening.