In your Mac's OS X operating software, the computer keeps a special file folder called Caches. Programs use it to save frequently used data, avoiding repeated downloads and improving overall speed. However, as time goes by, data in cache can accumulate, consuming large amounts of space on your computer's hard drive. And if you don't use a program for an extended period, the data remains. You can check the cache either through the Mac's built-in Finder program or through convenient third-party software.
Back Up First
Before you change or remove any files in Caches, it's a good idea to perform a Time Machine backup. This ensures you can later recover files that might have been removed by mistake.
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Using the Finder
The Finder program, included with every copy of OS X, is a file browser and manager. To start it, click the Finder icon in the Dock. Click the Finder's Go menu, then hold down the Alt key and click the Library menu item that is revealed. Locate the Caches sub-folder and right-click on it, then click the Get Info menu item. A window appears that shows information about the sub-folder, including the number of megabytes or gigabytes of data in it. If this is several gigabytes in size and your hard drive is running low on free space, seriously consider deleting some of the older files in Caches. You can double-click the Caches sub-folder to open it; Finder displays a list of all the sub-folders in Caches.
A number of third-party vendors offer software programs, some at no charge, that monitor and clean the cache files on your Mac, among other tasks. Programs include Titanium Software's OnyX, Northern Softworks' Yosemite Cache Cleaner and Maintain's Cocktail. These programs automatically scan through the Cache files and let you remove them.
The Mac has a Safe Boot option that checks the health of the computer and, among other tasks, clears out cache files related to system updates, as well as font-related cache files. If you've been having problems with the appearance of fonts, either on the display screen or printed, your Mac may need the font cache reset. To do a Safe Boot, restart the Mac and hold down the Shift key when you hear the boot chime. Note that Safe Boot takes much longer than a normal restart, as it performs extra maintenance functions, particularly with the hard drive. And because Safe Boot temporarily disables Wi-Fi, USB connections and other features, you may not be able to do normal work until you restart the Mac in the regular way.
In addition to the Mac's built-in software, many third-party application programs keep data in cache; some of these, such as Web browsers, give you the option to clear the cache. Web browsers save images and other data onto your hard drive, speeding up your browsing experience but also sometimes leading to problems with complex Web pages and slowly filling up your hard drive. Each browser program has its own menu commands for managing cache files.