How do I adjust the brightness on my monitor?

I have a MacBook Air and it is connected to a monitor from Acer. I tried adjusting the brightness on both screens but it only changes the brightness on my MacBook.

Solution 1:

Unfortunately, there is no native way to change the brightness on the (non-Apple) monitor without using the OSD on the monitor. However, there do exist various third-party apps that can do this for you!

I personally use Lunar, which will allow you to change the brightness/contrast on the monitor from your MacBook. Instead of changing the display output (effectively dimming each individual pixel before sending it to the monitor), it uses a feature called DDC, which is on nearly every modern monitor. This allows it to directly change the brightness and contrast, same as you would using the monitor's OSD.

You can map Lunar's brightness and contrast controls to function keys, so you can control the brightness from your keyboard. It also has some more advanced features like syncing the brightness to the brightness on the MacBook's display or change it based on sunrise/sunset times, but it looks like those features are now paid unfortunately.

There are other options out there, like MonitorControl, but I don't have any personal experience with them.