Scroll Split

Natural scrolling on the trackpad. Classic scrolling on the mouse.

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Why

macOS has one "Natural scrolling" setting, and it applies to the trackpad and the mouse together. If you like natural scrolling on a trackpad but classic scrolling on a mouse wheel, macOS cannot do it.

Scroll Split fixes this. Turn Natural scrolling on in System Settings, and Scroll Split reverses only the scroll events that come from a mouse wheel. The trackpad keeps the natural direction, and the mouse gets the classic direction.

It is a tiny background app (about 100 lines of Swift). It has no window, no Dock icon, and no settings.

How it works

Scroll Split uses a Quartz event tap to watch scroll events. A trackpad sends scroll events with a gesture phase or a momentum phase. A mouse wheel sends events with no phase. Scroll Split reverses the events with no phase and passes all other events through unchanged.

Requirements

• macOS 13 or later
• Xcode Command Line Tools (xcode-select --install)

Install

1. Turn on Natural scrolling in System Settings > Trackpad > Scroll & Zoom.
2. Clone the repo and run the installer:

   git clone https://github.com/EduardsE/scroll-split.git
   cd scroll-split
   ./install.sh

3. Open System Settings > Privacy & Security > Accessibility and turn on Scroll Split. If it is not in the list, click + and select /Applications/Scroll Split.app.

The installer builds Scroll Split.app, copies it to /Applications, and adds a LaunchAgent so it starts at login. After you give the permission, Scroll Split starts on its own within about 15 seconds.

To open the Accessibility settings directly:

open "x-apple.systempreferences:com.apple.preference.security?Privacy_Accessibility"

Uninstall

./uninstall.sh

Then remove Scroll Split from System Settings > Privacy & Security > Accessibility.

Test without installing

./build.sh
"build/Scroll Split.app/Contents/MacOS/ScrollSplit" --verbose

--verbose prints mouse or trackpad for each scroll event. When you run it from a terminal, macOS checks the Accessibility permission of the terminal app, not of Scroll Split.

Options:

• --verbose: print each scroll event.
• --vertical-only: reverse only vertical scrolling on the mouse, not horizontal scrolling.

Troubleshooting

• The mouse still scrolls the wrong way. Run the test above. If the mouse shows up as trackpad, your mouse software (for example smooth scrolling in Logi Options+) sends trackpad-like events. Turn that feature off.
• Nothing changes. Check the log at ~/Library/Logs/ScrollSplit.log. If it says it is waiting for permission, turn on Scroll Split in the Accessibility settings.
• It stopped after a reinstall. Each build has a new ad-hoc signature, so macOS can drop the permission. Turn it off and on again in the Accessibility settings.
• Do not run two scroll tools together. If another app also reverses the mouse (Mac Mouse Fix, Mos, LinearMouse, Scroll Reverser), the two reversals cancel out.

Notes

• A Magic Mouse sends phases like a trackpad, so it keeps the natural direction.
• Tested with a Logitech MX Vertical and a MacBook trackpad.

License

MIT