Your laptop screen is brighter than your external monitor because each display has its own separate backlight and brightness control. The laptop panel is set by the operating system, while the external monitor is controlled mainly by its own buttons or on-screen menu. Raise the external monitor's brightness with its physical controls, and check that it is not in a power saving mode.
Why this happens
- The two screens are independent. The laptop panel and the external monitor each have their own backlight set to different levels.
- The Windows and Mac brightness keys usually control only the built in laptop screen, not the external monitor.
- External monitors are adjusted through their own on-screen menu, and that brightness may simply be set low.
- An eco or power saving mode on the monitor can cap its brightness.
- Different panel types and ages have different maximum brightness, so one can look dimmer even at full setting.
Is this normal?
Yes. It is completely normal for two separate displays to have different brightness, since they are controlled independently.
Does it cause any problems?
No damage, but a big brightness gap between screens is tiring on the eyes as you look back and forth, so matching them is worth it.
How to fix or check it
- Use the physical buttons on the external monitor to open its on-screen menu and raise the Brightness setting.
- Turn off any Eco, power saving, or automatic brightness mode in that menu.
- On Windows, the built in brightness slider may not affect the external monitor, so rely on the monitor buttons.
- To control an external monitor from Windows, some monitors support DDC/CI, which lets certain tools or Windows adjust brightness, so enable DDC/CI in the monitor menu.
- On a Mac, System Settings, Displays offers a brightness slider that works with many external monitors, so try that first.
- Compare both at full brightness. If the monitor is still much dimmer, its panel may simply have a lower maximum, which is a hardware limit.
Frequently asked questions
Why do my brightness keys not change the external monitor?
The keyboard brightness keys usually control only the laptop's built in screen. External monitors are adjusted through their own buttons and on-screen menu.
Can I control external monitor brightness from my computer?
Sometimes. If the monitor supports DDC/CI, macOS and some Windows tools can adjust it. Otherwise you use the monitor's physical controls.
Why is my monitor dim even at 100 percent?
It may be in an eco or power saving mode, or its panel simply has a lower maximum brightness than your laptop screen. Disable eco mode first.