As you use your Mac, it tends to accumulate lots of files--not just the ones you create and interact with, but preference and application support files, software downloads, and more. Even when these files become obsolete, they stick around, following you when you upgrade your OS or even move to a new machine. As a result, many of us have thousands of old, unneeded files--a.k.a. "cruft"--cluttering our hard drives.
In most cases, these outdated files do no particular harm. However, they can become a problem if your hard drive starts running out of room. (Yes, drives are getting bigger all the time; we're also loading them with more, ever-larger files.) They can also increase the time and storage space required for backups; slow down disk repairs, virus scans, and other maintenance chores; and clutter up Spotlight searches. In rare cases, forgotten files can even cause software conflicts, leading to crashes and other misbehavior.
In short, you have plenty of good reasons other than general tidiness to clear out the cruft on your Mac's disk periodically. Here are some suggestions for doing just that.
Where cruft accumulates
Obsolete files can appear just about anywhere, but a few locations in particular are cruft magnets. Two of the worst are your personal Preferences folder (/Users/yourusername/Library/Preferences) and, to a lesser extent, your system-wide Preferences folder (/Library/Preferences). Virtually every time you download and run a new application, it stores a preference file, or several, in one of these locations.
Similarly, the Application Support folders in /Users/yourusername/Library and /Library house helper programs, plugins, and other items that for one reason or another can't be stored inside the corresponding applications themselves (but don't belong in the Preferences folder, either). In lieu of the Applications Support folders, some applications create folders at the top level of your /Users/yourusername/Library or /Library folder (or both). Still other software uses normally hidden locations, such as /usr and /var (and subfolders within them).
When you delete an application by dragging it to the Trash, that doesn't do anything to all these extra files stored apart from the application itself. As a result, orphaned preference and support files are common.
That said, it can be tricky to determine which files are truly unneeded; a file's age alone may not reveal its importance or frequency of use. Luckily, a number of tools exist to help you find and delete just the right files.
Uninstallers can remove applications you still have on your disk but don't use anymore, and in some cases, can clean up the residue left after manually dragging an application to the Trash. But a word of warning: these tools aren't foolproof. Because the possibility of misidentification exists, I strongly recommend performing a full backup of your disk before undertaking a decluttering run.
A few Mac applications, including Microsoft Office and most Adobe applications, include uninstallers within their application folders. Some other applications have uninstallers on the disc or disk image; if the program came with an installer, launch it and look for an uninstall option. For everything else, several different utilities can uninstall arbitrary third-party software on OS X, including preference and support files, caches, Dashboard widgets, and logs. Although these utilities vary in thoroughness and accuracy, they're all easier to use and more reliable than searching your disk by hand.
For example, Synium's $15 CleanApp shows you not only the files it thinks should be deleted, but also files that other CleanApp users chose to delete when removing the same application. (Sending information about your applications to the company's server is optional and anonymous.) It can also identify orphaned support and preference files from applications you've already deleted.
Reggie Ashworth's $8 AppDelete also identifies such orphans. And it (along with Noodlesoft's $22 Hazel and Kumaran Vijayan's free AppTrap) watches the Trash; when you throw away an application, they offer to uninstall all its associated files too. AppZapper ($13) finds associated files when you drag an application onto its icon, and makes a satisfying zapping sound when you delete them.
Uninstallers show you what they propose to delete before going through with it, letting you deselect files you want to keep (and, in some cases, select more files for deletion). If you use one, be sure to review its choices before you click Delete; you may find some files that are shared with other applications or are otherwise still needed, even if the uninstaller thinks they can go.
Looking for other clutter
Uninstallers can only take you so far, because even the best of them can't read your mind. To take your cleanup to the next level, there are a few other things you can try:
* Check your Users/yourusername/Documents, Users/yourusername/Downloads, and Users/yourusername/Library/Mail Downloads folders for any items you no longer need (such as disk images for programs you've already installed) and drag them to the Trash.
* There are several utilities that will help you identify particularly large files, including the open-source GrandPerspective (free), Whatsize ($13), the Omni Group's OmniDiskSweeper (free), and Daisy Disk ($20).
* Trim down existing applications using J. Schrier and I. Stein's free Monolingual utility, which can remove language resources you don't need. It can also remove application code that's specific to either Intel or PowerPC processors, but I'd warn against using that latter option: there have been too many reports from users who trimmed apparently unnecessary code, only to find their apps no longer worked.
When you're finished deleting unused items, be sure to choose Finder > Empty Trash to free up the space on your disk that those files occupy.
Senior contributor Joe Kissell is the senior editor of TidBits and the author of Mac Security Bible (Wiley, 2010).
This story, "How to Unclutter Your Hard Drive" was originally published by Macworld.