hidpi-scale

Free flexible HiDPI scaling for external monitors on Apple-silicon Macs.

macOS caps most 1080p (and many other) monitors at their native "looks like" resolution, so everything is big and there's no smaller option in System Settings. Apps like BetterDisplay fix this behind a paid "flexible scaling" feature. hidpi-scale does the same thing for free: pick a scale step and get smaller UI and more screen space on the monitors you choose.

Here it is running on a 1080p DELL P2422H — macOS happily offering 2304×1296 and 2560×1440:

Setup

Requires macOS on Apple silicon, Homebrew, and Xcode Command Line Tools (xcode-select --install).

npx github:ankithans/hidpi-scale

or manually:

git clone https://github.com/ankithans/hidpi-scale.git
cd hidpi-scale
./install.sh

Out of the box it targets the DELL P2422H. For other monitors, add a line to models.conf (see below), then restart the daemon.

Usage

~/.hidpi-scale/set-scale.sh medium   # 20% more space (default)
~/.hidpi-scale/set-scale.sh large    # 33% more space, smallest UI
~/.hidpi-scale/set-scale.sh small    # ~7% more space
~/.hidpi-scale/set-scale.sh native   # panel's normal size
~/.hidpi-scale/set-scale.sh 1296     # or a "looks like" height; snaps to a step

The size you pick is remembered and re-applied automatically.

Choosing which monitors it affects

models.conf lists the monitors to scale, one per line, as vendor:model:panel-resolution (decimal EDID ids):

4268:41413:1920x1080   # DELL P2422H

Only exact vendor+model matches are ever touched — every other display is ignored. Any unit of a listed model works (useful when hot-desking). Find your monitor's ids with BetterDisplay's display info panel or ioreg -lw0 | grep -A9 DisplayAttributes. After editing, restart the daemon: launchctl kickstart -k gui/$(id -u)/com.hidpiscale.

How the automatic part works

• vdisplay is a small daemon (started at login by a LaunchAgent) that creates two headless virtual displays with HiDPI modes generated for each panel in models.conf, using the same private CGVirtualDisplay API that BetterDummy/DeskPad use.
• The daemon also watches macOS display-reconfiguration events. When the set of connected matched monitors changes — plug, unplug, dock, boot — it waits 3 seconds for things to settle and runs set-scale.sh.
• set-scale.sh mirrors each matched monitor onto its own virtual display (explicitly, via mirror, so two identical monitors never merge into one mirror group). macOS renders the desktop at the virtual display's resolution and downscales it onto the panel. With one monitor connected, the spare virtual display is parked inside the same mirror set so no invisible desktop is left floating.

With two monitors, the first detected unit goes right of the built-in display and the second goes left. To pin specific units to specific sides, create local.conf next to the scripts (see local.conf.example).

Notes

• The panel keeps its physical resolution — text gets smaller and slightly softer the higher you scale. "medium" is a good balance; bumping the monitor's own OSD sharpness helps.
• Supports up to two matched monitors at a time.
• Uses a private CoreGraphics API for the virtual displays; it may break in a future macOS release.

Uninstall

~/.hidpi-scale/uninstall.sh

License

MIT