MacRes4K

A focused macOS menu-bar utility for switching a 4K display between
crisp 1080p HiDPI desktop mode and native 4K gaming mode.

MacRes4K does one job: it switches the macOS main display between two exact resolution modes.

• 1080p (1920×1080 HiDPI) — 1920×1080 logical points rendered with 3840×2160 physical pixels for a sharp, comfortable desktop.
• 4K (3840×2160 Native) — 3840×2160 logical points and physical pixels so games can see and render at native 4K.

It was built for games running through CrossOver, where changing the in-game resolution does not always change the macOS desktop resolution first. Some native macOS games behave the same way. MacRes4K makes the pre-game switch—and the return to a readable desktop—a two-click operation.

Download

Download the universal Apple silicon + Intel build from the latest GitHub release.

This is an ad-hoc-signed personal build rather than a notarized App Store distribution. The full source is available here for inspection and local builds.

Features

• Lives only in the menu bar: no Dock icon and no app windows.
• Controls only the macOS main display.
• Matches the exact logical and physical dimensions of each preset.
• Never selects an ordinary low-resolution 1920×1080 mode.
• Preserves the current refresh rate when possible, otherwise choosing the highest available rate.
• Shows a checkmark only beside the mode that is actually active.
• Tracks display changes, sleep and wake, reconnects, and changes made in System Settings.
• Starts each app session in 1080p HiDPI and restores it before quitting.
• Offers to remain running if that final restore fails.
• Registers as a Login Item when installed in an Applications folder.

Install

1. Download and unzip MacRes4K-1.1-universal.zip from Releases.
2. Drag MacRes4K.app into /Applications.
3. Control-click the app and choose Open the first time if Gatekeeper asks for confirmation.
4. Approve MacRes4K under System Settings › General › Login Items if macOS requests approval.

The app requires macOS 13 or newer and a main display that exposes both exact modes. If either mode is unavailable, both resolution actions remain disabled.

Build from source

Open MacRes4K.xcodeproj in Xcode and run the MacRes4K scheme, or build from Terminal:

xcodebuild -project MacRes4K.xcodeproj \
  -scheme MacRes4K \
  -configuration Release \
  -destination 'generic/platform=macOS' \
  -derivedDataPath build/DerivedData \
  build

The Release app is written to:

build/DerivedData/Build/Products/Release/MacRes4K.app

Run the unit tests with:

xcodebuild test \
  -project MacRes4K.xcodeproj \
  -scheme MacRes4K \
  -configuration Debug \
  -destination 'platform=macOS' \
  -derivedDataPath build/DerivedData

How it works

MacRes4K is a native Swift/AppKit app built on CoreGraphics:

1. It enumerates the main display's desktop-usable CGDisplayMode values.
2. It classifies only exact 1920×1080 logical / 3840×2160 physical HiDPI and exact 3840×2160 logical / physical native modes.
3. It establishes 1080p HiDPI as the CoreGraphics session baseline.
4. Native 4K is applied as an app-lifetime override, allowing CoreGraphics to return to the baseline if the process exits unexpectedly.
5. It observes display and workspace notifications so the menu always reflects the active mode.

The mode-classification and selection logic is isolated from CoreGraphics and covered by unit tests for exact matching, low-resolution rejection, refresh-rate selection, and checkmark state.

Project story

Read the Real World AI Lab field note, Building MacRes4K with Codex: A Two-Choice Menu Bar Fix for 4K Mac Gaming, for the problem behind the app and how our earlier Xcode work on Morrowward helped Dave, Codex, and GPT turn the idea into a finished utility.

Privacy

MacRes4K is entirely local. It has no analytics, accounts, network service, or data collection.

License

MacRes4K is available under the MIT License.

Built by Dave Isbitski.