There are well over a million files on my Mac. Sure, a few hundred thousand of those are components of OS X itself or of the apps I've installed. But, still, the number of user-generated files I've accumulated over the years astonishes me.
Most of the time, those files just sit there minding their own business, bothering no one. But sometimes, say, when I do a Spotlight search for a document and thousands of potential matches pop up, I start thinking a bit of file-simplification is in order.
Now, in this context "simplify" could mean "delete"--but it doesn't have to. I might need a certain old file only once in a span of several years, but that doesn't make it safe to delete. Depending on the context, simplification might mean reorganizing files, creating archives, offloading files to an external disk, or other strategies. And, of course, it would be easy to get carried away with this sort of thing and spend endless days looking for every last way to optimize one's files, but that's sure to produce diminishing returns. Instead, I suggest concentrating on the easiest and most fruitful kinds of simplification.
Reasons to simplify your files
Ease of finding documents isn't the only reason to simplify your files. Greater numbers of files also make activities such as backups, syncing, disk repair, upgrading OS X, and migrating to a new Mac more time-consuming. And, needless to say, all those files take up space, which is especially significant for anyone whose Mac laptop has a low-capacity SSD.
Simplification can also benefit you if you collaborate with other users, whether through a cloud-syncing service such as Dropbox, using OS X's built-in file sharing, or relying on a file server. The more easily your colleagues can locate documents, and the less pain they have to go through to sync and store them, the happier they'll be.
Which files to simplify
You'll have to decide for yourself what's working and what isn't when it comes to your files, but I'll give you a few examples of file types that are high on my simplification list.
Many versions of a single document: When I write a book or article, the file goes through numerous iterations as it bounces among author, editors, tech reviewers, and publisher. Sometimes I have several dozen versions of a manuscript before I'm done. In most cases, only the final version is useful, but occasionally I need to check back and see who made a certain change and when. My preferred strategy for dealing with those old versions is to wrap them up in a Zip file (select them in the Finder and choose File > Compress X items) and then trash the originals.
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.