Can I run a virtual screen at 120 Hz?

You can add a 120 Hz mode to a virtual screen, but selecting it does not guarantee that a mirrored or streamed image delivers 120 distinct frames per second. The advertised virtual rate and the image actually presented on the physical monitor are separate parts of the display path.

Open Settings > Displays > [virtual screen], enable Custom refresh rate list, and use Add Refresh Rate to enter 120. This configuration requires Pro. Keep a 60 Hz entry as a fallback, apply the requested virtual-screen reconnect, then select the intended resolution and refresh rate in the app menu. Reconnecting temporarily removes that virtual desktop.

The default list supplies 60 Hz modes. Custom entries can range from 24 to 240 Hz, but macOS and the Mac's virtual-display support determine which modes work. The physical monitor and its connection must also support the desired output rate. Changing the virtual list does not upgrade that connection.

If motion stutters, frames repeat or the picture develops artifacts, compare 60 Hz at the same desktop size. A reported 120 Hz value or a browser timing counter alone does not establish that the complete mirror or stream path is presenting 120 different frames each second. Results can differ with the Mac, macOS, desktop size and presentation method.

Mirroring can also change the physical target’s refresh-rate choices, including VRR. To expose its separate mode menus, enable Settings > Menu > Allow resolution change for mirror target displays, then inspect the target’s Refresh Rate menu. This permits low-level changes and lets resolution/refresh-rate protection apply to mirror targets. It does not create a missing VRR mode or guarantee stable mirroring. Verify the resulting physical mode and its behavior after reconnecting.

See Virtual Screen refresh rates for mode configuration, and virtual-screen performance for scaling and presentation tradeoffs.