How to Defrag a Mac Hard Drive. Defragging a Mac hard drive is a thing of the past because of the way that OS X manages files. After installing system updates or new applications, the computer will optimize itself. There are ways to periodically clean up your computer and defrag a Mac hard drive, but it can take a few hours and may not improve performance significantly.
Defrag a Mac Hard Drive
Open the Disc Utility program, which is located in the "Utilities" folder of your "Applications" directory. Highlight your hard drive from the list and have the program repair the permissions. This is an easy way to correct some common computer errors which could be slowing your hard drive down.
Look for a program to defrag your computer. There are some free utilities that can work on your Mac hard drive, but you should seriously consider purchasing a program because of the stability and support that comes with a purchased product. Defragging programs include Disc Warrior and iDefrag (see Resources below).
Take steps to back up your data before you defrag a Mac hard drive. Data loss is unlikely with well-respected programs, but defragging is a long and extensive process, and you can never be too safe.
Plan to run your defragging program during a time when you won't need to use your computer. No matter which program you decide on, it can take up to several hours to defrag a Mac hard drive. Some companies even suggest running the program overnight.
Notice whether defragging your Mac hard drive improved your computer's performance. Opening applications and large files should be faster if only by a few seconds. If your hard drive is more than 75 percent full, the performance increase may be more noticeable.
OS X automatically defrags files that are less than 20 megabytes. These files will make up the majority of your computer, unless you use it for specialized tasks such as software compiling or high-quality graphic design. Backing up your documents and then erasing the computer's hard drive can be a crude, but inexpensive and effective way of defragging it. Be sure that a defragging program can give you a detailed report of what was changed and how many files were affected by the process. Clearing your computer's various caches, including those associated with your Internet browser, can also help speed up your machine.