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 panel can be dimmed from Settings > System > Display > Brightness, or with the slider in the action center. That part is easy and Windows handles it natively.
External monitors are a different story. Windows generally has no control over them at all, so you are reaching for the physical buttons or on-screen display (OSD) menu on the monitor itself every time you want to adjust it. Some monitor vendors ship their own utility for this, but it only works with that one brand, and there is no single Windows setting that controls brightness across every monitor you have plugged in.
The faster way with AppRig
AppRig’s Brightness sub-tool auto-detects both built-in panels and any external monitor that supports DDC/CI, the protocol most monitors use to accept software brightness commands. Each display gets its own slider, plus an “All monitors” master that adjusts every screen together while preserving the brightness offset between them.
It also handles a few rough edges that plain DDC/CI control does not: it can calibrate a monitor whose panel saturates before it hits 100 percent, remember your preferred levels across restarts, and automatically adjust brightness by time of day. None of it requires reaching for the monitor’s buttons.
See the full AppRig how-to in the docs →
Related questions
AppRig does this and more, all in one local-first Windows app. See what AppRig does →