How to Put Your Mac on a Diet With Xslimmer

Everyone knows that apples are a healthy food—hence the saying “an apple a day keeps the doctor way”. But people rarely think to ask what Apples eat. When your Mac starts gobbling up too much fattening hard drive space, it’s time to call in a different kind of doctor. One that goes by the name of “Xslimmer”.

Xslimmer is a simple, effective application for safely reclaiming the surprisingly large amounts of hard drive space that can get taken up by parts of applications you don’t actually need. It’s not a compression app, although its developer LateNiteSoft also makes a product called Squeeze that compresses your files in place. Instead, Xslimmer frees up hard drive space by stripping unneeded translations and binaries from your applications.

A Look Behind the Scenes

Confused? Feel skeptical about being able to delete parts of software without blowing something up? I don’t blame you—I felt the same way the first time I used Xslimmer. An understanding of exactly what’s going on may help you feel a little bit more relaxed.

Language Files

Most applications, both those made by Apple and those made by other developers, come packed with everything they need to survive in any environment they may encounter. For one thing, they often include as many translations as the developer can afford or find volunteers to create. That may mean there are help and interface files for—in the case of Apple applications—up to eighteen languages. If you only use one (or even two or three), Xslimmer can delete the files for the other seventeen or so without endangering your application at all.

Universal Binaries

Another feature of many applications is that they ship as “universal binaries”. While some new Apple fans may be more familiar with “universal binaries” referring to applications that can run on both the iPad and the iPhone with a different interface on each, the term is rather older than that.

A few years ago, when Apple switched its entire Mac lineup from the PowerPC processors that were quickly becoming obsolete over to incompatible Intel chips, Apple started encouraging developers to ship their applications as two separate binaries (one to run on PowerPC Macs, and one to run on Intel Macs) jammed into the same app.

That way, users wouldn’t have to worry about which kind of processor they had—they could just download one big application and be sure it would run, no matter what.

32 & 64 Bit

A few developers even went a step further—they optimised their code separately for 32- and 64-bit PowerPC processors, and again for 32- and 64-bit Intel processors. The end result can be applications that are nearly four times as large as they need to be to run on one particular computer.

Xslimmer can strip out any binaries that aren’t needed for your particular machine. Doing this kind of cleaning up can be dangerous to certain applications, but for the most part the hard drive space savings make up for the few reinstallations you may need to make.

How Does Xslimmer Work?

Xslimmer has a very simple interaction model: you drag applications into it, you tell it to slim them, and it slims them. Really. That’s about as complex as it needs to be.

You can either drag apps directly into Xslimmer from Finder, if you have just an app or several you want to slim, or you can take advantage of Xslimmer’s genie feature. Genie does a once-over of your computer, finds just about every application that isn’t required for the system or part of Apple’s Developer Tools, and offers to slim all of them at once.

There are certain applications that, for one reason or another, Xslimmer can’t slim. Some are blacklisted applications like Dropbox and pretty much everything by Adobe; those are applications that will break if Xslimmer tries to slim them.

LateNiteSoft does a pretty good job of blacklisting breakable apps and Xslimmer has been around for a good while, so you shouldn’t have to worry too much about it accidentally breaking any applications unless you’re using something brand new that it hasn’t seen before.

You may also encounter apps that “cannot be slimmed further”; that should only happen if you’ve used Xslimmer or a similar tool before. Finally, there are certain applications that require an administrator password to slim. These are almost always Apple applications or apps placed by an installer rather than dragged and dropped into the Applications folder by a user. This is just a side effect of how installers work on OS X; those apps are no more likely to get broken than any other.

Next to each application there is a globe or set of globes, showing whether that application has languages that can be trimmed, and a “universal binary” or processor icon indicating whether there are unnecessary binaries that can be stripped.

By default, Xslimmer will try to strip both of these from each application, although it can be ordered to leave one or the other alone in the Preferences. You can also choose to get info on any app, to get a clearer picture of exactly how much space will be freed by slimming it, as well as how it will be freed.

The clear button will handily clear out apps that can’t be slimmed. You can easily add or remove apps from the list using the plus and minus buttons at the bottom left, and then you’re free to start slimming.

The first time you hit the Slim! button, you’ll be confronted with a warning that offers to make backups of all of your applications before slimming them:

This is potentially useful, but it does sort of defeat the purpose of clearing out hard drive space. I’ve come to trust Xslimmer pretty completely, and I no longer make backups before slimming.

Once Xslimmer has freed a gig or two of space for you, your slimming history lives under History (shock), just in case you ever need to know—for example—exactly when you stripped down Firefox. That’s almost the end of what the app can do.

Using the preferences, it can also automatically compress newly slimmed apps using Snow Leopard’s transparent compression technology, choose which binaries you want to trim (all except the native ones, or all except the very best ones), exclude certain apps and folders from having their content slimmed, choose where backups are kept, and pick which languages you want to keep around.

Why Xslimmer?

There are several applications with similar features to Xslimmer. First is Monolingual, a free and open source app that accomplishes the same goals, but in a less well-designed interface. Trimmit can only handle one application at a time, but trims out some things even Xslimmer misses. Unfortunately, it takes approach of drag-and-drop simplicity even further, to the point where there’s no blacklist or other feature protecting your apps from being nuked by a careless trim. Trimmit is best used in concert with Xslimmer to cut slimmable applications down even further.

Xslimmer is a brilliant and quite safe (and at $14.95, relatively inexpensive) standalone method of putting your Mac on a diet and regaining some lost hard drive space. If your hard drive space is at a premium, or if you often make fresh installs, Xslimmer can be an invaluable maintenance tool.