The purple outline rectangles that appear around UI elements (buttons, search fields, menus) are not a mouse selection bug.
They are macOS focus rings, and they appear when:
- Full Keyboard Access is enabled, or
- Keyboard navigation has been toggled on accidentally.
You can toggle this on without noticing by pressing:
Control + Option + Command + F5
or
Control + F7 (older shortcut)
Both toggle Full Keyboard Access on/off.
When it's on, macOS draws a highlighted rectangle around the currently selectable UI element — exactly like the one in your screenshot.
Using Settings
- Open System Settings
- Go to Accessibility
- Click Keyboard
- Enter Keyboard Navigation or Full Keyboard Access
- Turn Full Keyboard Access → Off