Apple’s MacBooks are thin, light, and portable, but they are also powerful systems that can provide a great computing experience at home. Thanks to features like Thunderbolt and accessories like docking stations, many users connect their MacBooks to a large external display and a mouse or trackpad. When connected to a mouse or wireless trackpad, a MacBook’s built-in trackpad will still work, providing a second method of cursor input. Depending on how you have your MacBook positioned, however, this may be troublesome, as a misplaced hand or the paw of your friendly household pet may trigger unwanted cursor movement.
Thankfully, you can configure OS X to automatically turn off your MacBook’s built-in trackpad when a mouse or wireless trackpad is connected, and then turn the built-in trackpad back on when you disconnect your mouse or trackpad and head out the door.
Disable a MacBook Trackpad in OS X Lion and Above
In all versions of OS X from 10.7 Lion and up (including OS X Yosemite), head to System Preferences > Accessibility > Mouse & Trackpad. There, find and check the box labeled Ignore built-in trackpad when mouse or wireless trackpad is present.
There’s no need to save or reboot; the new option will take effect immediately. With this box checked, your MacBook’s built-in trackpad will be automatically turned off when you connect a mouse (USB or wireless) or a wireless trackpad to your Mac. The built-in trackpad will automatically start working again once the mouse or external trackpad is disconnected.
Disable a MacBook Trackpad in OS X Snow Leopard
Although the outcome is the same, the process to enable this option is a little bit different for Snow Leopard. Head to System Preferences > Universal Access > Mouse & Trackpad. There, find and check Ignore built-in trackpad when mouse or wireless trackpad is present.