BetterDummy

Dummy Display for Apple Silicon/Intel Macs to Have Custom HiDPI Resolutions - an app from one of the makers of MonitorControl.

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About

M1 macs tend to have issues with custom resolutions. Notoriously they don't allow sub-4K resolution displays to have HiDPI ("Retina") resolutions even though (for example) a 24" QHD 1440p display would greatly benefit from having an 1920x1080 HiDPI "Retina" mode.

To fix this issue, some resort to buying a 4K HDMI dummy dongle to fool macOS into thinking that a 4K display is connected and then mirror the contents of this dummy display to their actual monitor in order to have HiDPI resolutions available. Others use the built in screens of their MacBooks to mirror to the external display. These approaches have obvious drawbacks and cannot solve all problems.

To fix this problem, BetterDummy creates a virtual dummy display which you can then utilize as a mirror main.

Advantages of BetterDummy over a physical 4K HDMI dummy plug or mirroring your internal display:

• Your HDMI port will remain usable for an other display on the Mac Mini.
• Your internal screen will be available as an extended space on a MacBook (or you can use clamshell mode).
• Does not suffer from issues that prevalent with the physical dummy (like jittery mouse cursor).
• Offers a much wider variety of HiDPI and standard resolutions.
• Works with all aspect ratios, does not depend on what resoluations are recorded in the dummy's EDID/firmware.
• Does not utilize graphics hardware in vain so it is somewhat faster.
• Available instantly.
• It is free (donations humbly accepted). :)

Some other possible uses:

• The app is also useful for anybody who is not satisfied with the offered default HiDPI resolutions offered by macOS - as in some cases this could be rather limiting - especially on Wide or UltraWide displays.
• Use headless Macs (servers) with any resolution and HiDPI mode for remote access (tested on Intel Mac with Intel UHD 630 - please note that the app runs in user space after login).
• Scale Sidecar resolutions.
• Better quality zooming (System Preferences»Accessibility»Zoom) or High Quality screenshots even on Full HD displays.
• You can use it instead of or alongside other apps that create custom native resolutions.

Usage

1. Start the app
2. In the app menu choose Create New Dummy and select your desired aspect ratio

3. In System Preferences -> Displays you'll see the new Dummy display (for example Dummy 16:9)
4. Activate mirroring. The Main display should be the Dummy display
5. Set the Dummy display as Optimize for
6. Set Resolution as Scaled - you should hold the Option key while clicking on the Scaled option for a fuller list of resolutions!
7. You can also click Show all resolutions for even more resolutions

9. Select the desired mode.

The app saves the dummy display configuration and automatically restores it upon next restart.

Notes:

• The tutorial was compiled on an Apple Silicon Mac running macOS Monterey (the app works on Intel and Big Sur as well - steps are slightly differnt, see this article on how to customize mirroring on Big Sur).
• For most configurations, you'll see HiDPI 'Retina' resolutions in the list by default and see and additional non-HiDPI resolutions marked with a (low resolution) tag in the resolution list if Show all resolutions is toggled. On some configurations however, you might see HiDPI (high resolution) display modes marked with a (HiDPI) tag and standard resolutions without a tag.
• You might have to fight a bit with macOS Monterey's new Displays tab in Preferences as the Optimize for setting tends to reset at random times to the physical display for unknown reasons during changing settings. If this happens, you can set it back to the Dummy.
• You may want to enable the System Preferences»Notifications & Focus»Allow Notifications»When mirroring or sharing the display option to allow notifications when mirroring is turned on.
• Please note that the app cannot "magically" increase the number of pixels on your display and is unable to make a 1080p display look like a 4K display (the only benefit for a 1080p display is better clarity in zooming or the ability to make high resolution screenshots).

Installation

• Download the latest release
• Move the app to Applications
• Start the app
• Use the app menu bar item to interact.

Compatibility

• The app should be compatible with all M1 class machines running macOS Monterey (MacBook Air, Mini, 2020 and 2021 MacBook Pros).
• The app is also compatible with Intel and macOS Big Sur (testing was limited to a single Intel Mac with Intel UHD 630 running Big Sur).
• The app is compatible with headless mode as well (this was tested on Intel).

Known issues

There are some issues which are related to limitations/issues in macOS itself:

• High refresh displays (refresh rates above 60Hz) are not supported.
• Only SDR content is supported.
• Mirroring any content to the internal display of the 2021 MacBook Pros will force the mirror under the notch.
• Due to a bug present in the current macOS versions, mirroring virtual displays (Sidecar, BetterDummy, etc) might cause sleep issues on some configurations. The app has some workarounds for this issue but these might not work on all configurations.
• Due to a bug present in the current macOS versions, swiping or keyboard shortcuts to switch spaces do not work on extended (secondary) mirror sets that involve virtual displays.

Some of these issues affect physical dummy mirrors as well.

How can I help?

Some of the options:

• You can contribute to the code (via Pull Requests)
• If you like the app, you can support the developer. :)
• Don't forget to star the GitHub page!
• Spread the word.

Thank you for your help, it is really appreciated! :)

Don't forget to check out

If you like this app, you'll like MonitorControl as well! Control the brightness, volume of your external display like it would be a native Apple display!

Discord channel

You can join the (mostly self help) discussion on the new BetterDummy discord channel.

Thanks

• @tml1024! - FluffyDisplay + reused adapted CGVirtualDisplay headers reverse engineered by @w0lfschild
• @JoniVR - MonitorControl + sparkle scripts
• @the0neyouseek - MonitorControl + sparkle scripts