Change Accessibility Mouse & Trackpad preferences on Mac
On your Mac, use the Mouse & Trackpad pane of Accessibility System Preferences to make your mouse and trackpad easier to use. The options available depend on the Mac you’re using.
To change these preferences, choose Apple menu 
> System Preferences, click Accessibility, then click Mouse & Trackpad.
Open the Mouse & Trackpad pane for me
Enable Mouse Keys | Use the keyboard instead of the mouse to control your Mac. Click Options to customize Mouse Keys: Press the Option key five times to toggle Mouse Keys: Use your keyboard to turn Mouse Keys on and off. Ignore built-in trackpad when Mouse Keys is on: Disable the trackpad on your Mac when you use Mouse Keys. Initial Delay: Set how quickly the pointer starts moving when you press a key. Maximum Speed: Set the maximum speed at which the pointer moves. |
Double-click speed | Adjust the mouse or trackpad’s reaction time when you double-click an item. |
Spring-loading delay | Use the slider to specify how long an item has to be over a folder before the folder opens. |
Ignore built-in trackpad when mouse or wireless trackpad is present | Disable the built-in trackpad on your Mac when you use a mouse or wireless trackpad. If you use a non-Apple mouse, the driver software that came with your mouse may prevent this option from working as expected. For information, see the documentation for your mouse. |
Trackpad options
Scrolling speed | Adjust the speed at which you scroll through documents and windows using the trackpad. |
Scrolling | Select the checkbox to turn scrolling on or off. Click the pop-up menu, then choose an option to control what happens when you lift your finger from the trackpad: with inertia: Scrolling comes to a gradual stop. without inertia: Scrolling stops immediately. |
Enable dragging | Select the checkbox to be able to drag items. To set dragging options, click the pop-up menu, then choose an option: without drag lock: Double-tap an item, then drag it without lifting your finger after the second tap; when you lift your finger, the item stops moving. The item can still be dragged for a fraction of a second (so you can reposition your finger if it’s at the edge of the trackpad). To immediately prevent further dragging, tap the trackpad once. with drag lock: Double-tap an item, then drag it without lifting your finger after the second tap; dragging continues when you lift your finger, and stops when you tap the trackpad once. three finger drag: Drag an item with three fingers; dragging stops when you lift your fingers. |
Mouse options
Scrolling speed | Adjust the speed at which you scroll through documents and windows using the mouse. |
Scrolling | Select the checkbox to turn scrolling on or off. Click the pop-up menu, then choose an option to control what happens when you lift your finger from the mouse: with inertia: Scrolling comes to a gradual stop. without inertia: Scrolling stops immediately. This option is available when you use a mouse such as a Magic Mouse. |
To quickly enable or disable Mouse Keys using the Accessibility Options shortcut panel, press Option-Command-F5 (or if your Mac has Touch ID, quickly press Touch ID three times).