How to Speed Up Mac Computers That Are Running Slowlyby Contributor ; Updated September 28, 2017
If your Mac is running slowly, it's frustrating. Although deleting large files to free up disk space may help, as can purchasing additional RAM for the computer, there is a step you can take using a Mac utility to speed up your Mac before you look at other options.
Go to the "Utilities" folder located inside your Mac's "Applications" folder.
Click on "Disk Utility." Select your hard drive from the list in the left panel; if you have two disks showing, repeat this process with the second disk after the first. After selecting a disk, click, "Repair Disk Permissions."
If you have two disks listed, run "Repair Disk Permissions" on the second disk as well.
Restart the computer. When it starts up again, your Mac should be running faster.