There are times when you might want to disable the built-in Trackpad on your MacBook, MacBook Air and MacBook Pro. For example, you’re more used to using a mouse as an input device, you’re using an external trackpad device, or the trackpad is having issues and behave erratically.
To disable the trackpad, go to System Preferences > Accessibility. Select “Mouse & Trackpad” and check the box “Ignore built-in trackpad when mouse or wireless trackpad is present”.
You will notice that there is no way to permanently disable the Trackpad. You will need an external mouse or input device in order to make the built-in Trackpad non-functional.