We often get issues like: "MonitorControl doesn't work with my monitor",
so here are some troubleshooting steps and general information to try and help you.

General Information

• MonitorControl doesn't work with every monitor, it all depends on how well your display/cable manufacturer implements the DDC/CI spec.
• Some displays will only support certain features well (for example, they work well with brightness but not volume).
• It also depends a lot on your hardware combination.

Troubleshooting

I can't control volume/brightness

Try a different ddc tool

First step you can try is a different ddc tool called ddcctl.
If your setup works with ddcctl it should also work with MonitorControl.
After installing ddcctl, try something like:

./ddcctl -d 1 -v 30

(tries to set the volume of display 1 to value 30) or

./ddcctl -d 1 -b 30

(tries to set the brightness of display 1 to value 30)

If these commands change your brightness or volume, you know that your display supports ddc (or at least the command that worked).

Try a different cable

If the first step didn't work for you, your next best bet is trying a different cable/connection.

Generally, people seem to have the highest succes rates with DisplayPort and the lowest with HDMI.

I can't get accurate read values from the monitor

If the monitor is unable to read values from the display, it will default to the last known values.

To try and fix this, you can try checking the Longer Delay option inside Preferences > Advanced.
See the Advanced Preferences wiki page for more information.

The app is slow on startup

This is usually because we poll the display to try and read its current volume/brightness on app launch.

You can lower or disable the Polling Mode inside Preferences > Advanced.
See the Advanced Preferences wiki page for more information.

I get screen flickering when launching MonitorControl

This can be caused due to trying to poll (read) values from your display multiple times. Try setting Polling Mode to none in Preferences > Advanced.