StickyKeys

StickyKeys is a native macOS menu-bar utility for one-shot modifier keys. By default, right-side modifiers act as sticky triggers, but you can switch the trigger side to left-side modifiers in Options....

• press and release the selected-side Shift, then press a key to apply Shift once;
• double-tap the selected-side Shift quickly to lock Shift for following keys, then press that Shift once to return to normal;
• press and release the selected-side Option, then press a key to apply Option once;
• press and release the selected-side Command, then press a key to apply Command once;
• with Enable modifiers for mouse click and scrolls turned on, the pending modifier is also applied to clicks, drags, and scroll events without consuming it;
• press Escape or press the same non-locking trigger twice to cancel the pending modifier.

While a modifier is pending, a non-interactive HUD in the top-right corner shows ⇧, ⌥, or ⌘. Locked Shift uses the same ⇧ symbol with a green dot next to it. It disappears when the modifier is used, cancelled, or unlocked.

Requirements

• macOS 13 or newer
• Xcode 15 or newer (the project is verified with the Xcode version reported by xcodebuild)

Build and run

1. Open StickyKeys.xcodeproj in Xcode.
2. Select the StickyKeys scheme and the My Mac destination.
3. In Signing & Capabilities, select your development team if Xcode asks for one.
4. Build and run with ⌘R. The app appears only in the menu bar.
5. Choose Options... from the menu and grant both Accessibility and Input Monitoring. Restart the app if macOS asks you to do so.

For normal use, archive/copy StickyKeys.app to /Applications before enabling Launch at Login. macOS permission records are tied to the signed app identity and location, so rebuilding or moving an unsigned Debug app can require granting permissions again.

Implementation notes

• A session-level CGEventTap consumes trigger events and mutates following key events. Mouse actions receive the active modifier flags without consuming pending state.
• The app handles keyboard, mouse button, drag, and scroll events. Modifier triggers normally arrive as flagsChanged.
• The Shift, Option, and Command keys on the selected trigger side are consumed as one-shot triggers, while their opposite-side counterparts continue to work as normal modifiers.
• App Sandbox is disabled because a suppressing global event tap is incompatible with the sandboxed app model.
• Preferences are persisted with UserDefaults; Launch at Login uses SMAppService.mainApp.