Troubleshooting guide
How to fix the problem
A Mac can mirror the display of two docked monitors, either due to the dock's MST technology or the Mac's own external display limit. The limits depend on the exact chip, model, and sometimes lid mode.
Possible solutions
Choose the method that matches your situation. Start with the simplest suitable option and check the result. If the problem is fixed, you do not need to continue with the other methods.
Checking Mac and Dock capabilities
Determine how many independent displays are supported.
Steps to follow
- In the Apple menu > About This Mac, write down the exact model and chip, such as M1, M1 Pro, or other.
- Check Apple's technical specification for the number and conditions of external displays. Just saying "MacBook" isn't enough.
- Look in the dock specification to see if the two displays work via MST, separate Thunderbolt streams, or DisplayLink.
- Compare manufacturer-specified macOS support with your Mac. If a combination is not supported, changing the settings alone will not make it supported.
Comparison of single and dual screens
Check if the duplication can be changed in the system.
Steps to follow
- Leave one monitor and go to System Settings > Displays.
- Connect a second one and see if the system displays two separate external displays or one.
- If both are separate, choose the extended desktop, non-duplication option. The name depends on the macOS version.
- If only one common display is visible, check another connection method supported by the model or a compatible dock; do not start by overwriting the system.
If the problem persists
If the selected dock is for two independent displays via MST, its behavior may be different on macOS than on Windows. Choose based on specific Mac support, and in the case of DisplayLink, consider add-on, permissions, and storage image restrictions.
Request a repair