How to adjust external monitor brightness on Windows
Short answer
Most external monitors only change brightness through the physical buttons on the monitor itself, because Windows cannot dim them by default. Monitors that support DDC/CI can be controlled in software, though. A tray app like AppRig detects DDC/CI displays and gives every monitor, external or built-in, its own brightness slider you can reach without touching the hardware buttons.
The manual way
A laptop’s built-in screen can be dimmed from Settings > System > Display > Brightness, or with the slider in Quick Settings. Windows handles that part natively.
External monitors are a different story. On most desktop setups the Settings slider simply is not there, and Microsoft’s own advice is to use the buttons on the monitor. So every adjustment means reaching for the physical buttons or joystick and digging through the on-screen display (OSD) menu. Some monitor makers ship their own utility, but it only works with that one brand.
What Windows does not tell you is that most modern monitors can take brightness commands from the PC over DDC/CI, the same cable that carries the picture. It is usually on by default; if not, it is a one-time switch in the monitor’s OSD menu, often under Setup or System. Windows just has no built-in slider for it.
The faster way with AppRig
AppRig’s Brightness tool detects your built-in screen and every external monitor that supports DDC/CI, and gives each one its own slider in the system tray. There is also an “All monitors” master slider that adjusts every screen together while keeping the difference between them, so a side monitor can stay dimmer than your main one.
It remembers each monitor’s level across restarts, and AppRig Pro smooths out two more rough edges of plain DDC/CI control: calibrating a monitor that stops getting brighter before 100 percent, and dimming and brightening your screens automatically by time of day. None of it needs the monitor’s buttons.
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Common questions
Why is there no brightness slider for my external monitor in Windows?
The brightness slider in Windows Settings is built for laptop screens, which Windows controls directly. Microsoft's own help page says you might not see the slider on devices that have an external monitor and tells you to use the monitor's buttons. An external monitor takes brightness commands over a separate channel called DDC/CI, so you need a tool that speaks DDC/CI to get a slider back.
Can I change monitor brightness without using the buttons on the monitor?
Yes, if the monitor supports DDC/CI, which most monitors made in the last decade do. It is usually switched on by default. If software cannot see your monitor, open the monitor's on-screen menu once, find the DDC/CI option (often under Setup or System) and turn it on. After that, brightness can be set from Windows without touching the buttons again.
What if my monitor does not support DDC/CI?
Then no software can change its backlight, and the physical buttons are the only true brightness control. As a fallback, the NVIDIA, AMD or Intel graphics control panel can lower the picture brightness or gamma, and Windows Night light can warm the colours in the evening. These darken the image rather than the backlight, but they help in a dark room.
How do I dim one monitor but not the other?
Give each monitor its own brightness control. With DDC/CI, every monitor is addressed separately, so you can dim a side screen while the main one stays bright. AppRig shows one slider per monitor plus an All monitors slider that moves every screen together while keeping the difference between them.
Related questions
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