Large files: Videos, music, and virtual machines from apps like VMware Fusion (, $60) are common space hogs, but sometimes it's the weird little things that take up vast amounts of space. For example, I like Ecamm's $30 Call Recorder for recording Skype conversations. But if you have it set to auto-record video chats (as I did), you may find yourself with a folder full of multi-gigabyte files in no time. So I switched it to record only on demand, deleted conversations I knew I'd never need again, and compressed the few that were still useful to me.
Installers: When I download software, I usually like to hang onto the installer so I can put it on my other Macs without having to download it again. I find that storing installers on a network device such as Connected Data's $99 Transporter from Connected Data ($99) or Apple's $289 AirPort Time Capsule () serves the dual purpose of getting them off my main Mac's disk and making them available to my other machines.
Downloaded media: I buy lots of music, TV shows, and movies from the iTunes Store, but those media files don't all have to stay on my Mac, because I can (almost) always download or stream it whenever I need it. Occasionally, though, Apple removes content from the iTunes Store such that you can't download it again even if you paid for it. So I prefer to offload my media to an external disk, just in case.
Try a utility
Certain other types of files hog space needlessly but are harder to identify. For example, caches, log files, and support files from discarded apps are usually safe to delete. But it's not a good idea to trash these files indiscriminately, partly because they may serve a useful purpose and partly because it can be challenging to figure out where all these files are and which ones you no longer need. In such cases, a utility may be helpful.
I've tried numerous disk-tidying utilities, including uninstallers (see Do uninstallers work?), duplicate finders, and general-purpose tools such as Titanium Software's free (donations requested) OnyX. My current favorite — with a qualification — is MacPaw's $40 CleanMyMac 2 ().
I like the fact that CleanMyMac can identify large and old files, delete caches and logs, uninstall apps, manage system extensions of various kinds, and even slim down an iPhoto library. However, I never accept the default "delete everything" options, because it often identifies files that look disposable but are actually important to me. So I carefully review its selections before letting it delete anything.
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