Remove unnecessary applications from starting up immediately by going to System Preferences > Users & Groups. Not only do they slow down your startup, but they continue to do so the whole time you’re on your Mac. When you start your Mac, a lot of things load up in the background. This will take approximately an hour and the computer will require Internet connection and power. Back up your data before any update to make sure all information and files on the computer are safe, and install the new operating system. The most recent macOS can be searched for in the App store. Older OS's tend to run slower than the newer ones, so keeping the OS up-to-date is a good way to make a computer run quicker. Delete files that are no longer important to free up space. Go through the files on the computer and see what can be moved to different external locations/cloud storage centers. Having a full hard drive makes it hard for the computer to function quickly and efficiently. This article documents some common causes of slow Mac performance and the fixes.