OnyX: Free System Maintenance Software for Mac

I must be entirely honest – up until about two weeks ago, I was in the pretentious group of Mac users that never really maintained or “spring cleaned” their computer. Once or twice a year, this would catch up with me and I’d be occasionally fed up with Finder delays and general sluggishness (I blame my crazy tendencies to try dozens of new applications on a whim.)

About two weeks ago, as recommended by a half dozen of my friends (and the Mac.AppStorm review), I installed CleanMyMac. The application removed over 25GB worth of logs, universal binaries, drivers, multilingual support and caches. The amazing amount of space I got back, and the associated speed bump, was impressive.

However, paying money for cleaning services still seems very Windows-like to many Mac users. If you aren’t ready to install a shareware application, but want to take a look at cleaning out some of the cruft around your Mac, join me after the break to give OnyX a try!

What’s OnyX?

OnyX is a well known program, and has been around since Mac OS 10.2 (Jaguar). When you install the program, you will need to agree to their “It’s not our fault” agreement, install the S.M.A.R.T. status bit and verify the startup volume before you begin using OnyX.

Smart Check

Smart Check

It is probably a good thing to verify your hard disk if you haven’t done it recently. It’s super easy to do, either with OnyX or Disk Utility. To do it without OnyX, just open your Applications folder, find the Utilities sub-folder and launch Disk Utility. Select your internal drive and click Verify Disk under the First Aid tab.

Once you have OnyX up and running, you will notice a few simple options to get your Mac squeaky clean. We’ll work through item by item to ensure you know what OnyX can do and what those operations will do to your computer.


If you have a fairly new Mac, you can use a hardware test feature to ensure your internal drive is running well. Known as S.M.A.R.T. Statuses, they are the first sign that your hard disk may be near failing, and can help prevent you from suffering massive data loss.

While it won’t work with external drives, it’s important to make sure your S.M.A.R.T. status is in the clear. If you don’t want to use OnyX, these statuses can be found in the Disk Utility program as well.



The next sub-tab checks the hard drive’s Volume Structure. This is the same function as Disk Utility’s Verify Disk. Should it pop up with a problem, you will either need to go hunting for the DVD which came with your computer, or if you can’t find it / don’t want to deal with the hassle of repairing it yourself, you can make an appointment at your local Apple Genius bar.

They’ll be happy to repair the drive for you, generally at no cost. When OnyX does this process, it may seem like your computer is frozen. This is normal. Don’t take the “volume needs to be repaired” message lightly – it probably does!

The final sub-tab runs through all of your Mac’s Preference Files. These store information that help programs remember their settings – like window layouts, particular user preferences and license keys.


Another mirrored feature from Disk Utility, Permissions cleans up any errors within your Mac’s file structure. Permissions generally relate to who has access to your files. For instance, if you have multiple user accounts, which programs and options the Standard account holders have compared to the Administrators.

Also, permissions are set on a per file basis- so should they get out of whack, it could prevent you from opening them. Another way permissions can cause problems relates to copying files between Macs… Either way, it’s another important cleaning step to run regularly on your Mac.

To help limit how much maintenance the average Mac user has to perform on their Mac, OS X has ‘Scripts’ built into the operating system. These are actions that your Mac will run on a daily, weekly or monthly basis.

Generally these scripts run on their own just fine – but I’ve seen situations where they stop working automatically for various reasons. OnyX will go ahead and force them all to run if you would like – and will also show the last time your computer decided to run them.



Finally, the Rebuild tab shows different options you have to fix issues relating to file-program association and different indexes. You can clear out the different file associations, so that uninstalled, pesky bundled digital camera software will stop trying to open all of your pictures.

You can also reset things like your .DS_Store files which tell your Mac where in the Finder window icons are placed. If your Spotlight search program has been running oddly, you can rebuild that, along with the Mail.app’s index of messages. Don’t feel the need to rebuild these unless you are actually having issues though.


Here, you can remove all the different cache files that have built up on your system. For instance, your web browser often stores media and images on your computer so going back to them will be faster the next time. This works similarly throughout your Mac.

OnyX has some presets set, which if you’re unsure, should be left as they are before running this process.

Clean Away!

Clean Away!


Unless you are a power user, go ahead and avoid this section of OnyX. It can be a tad bit confusing and is unnecessary to help your computer run quickly.

If you are interested, these utilities will help you permanently show or hide volumes, adjust UNIX Manuals, empty the trash securely, and deal with Databases stored around your computer.


This is the central point of the application for non-power users. To go and clean all of the different zones in your Mac, this is place to go. It will let you empty caches and run the maintenance scripts and programs quickly and easily.

Cleaning everything isn’t going to hurt your machine. You’re not at a risk of losing data or causing your machine to crash. So, if you feel ambitious or just want to be super thorough- go ahead and check everything before pressing Execute.

It will take some time for your machine to rebuild caches and indexes, so for a short time it may seem as if your machine is running slower than before. This is temporary – don’t worry!

Setting up an automated process

Setting up an automated process

Parameters and System Information

OnyX also lets you set the global settings of many popular applications on your Mac. These settings include Finder, Safari, iTunes, Quicktime and more. The Info tab provides the same detailed information as the system profiler – just in case you find a need to brag about your RAM or Video memory size. It will also allow you to quickly find your serial number and UUI (Universal Unique Identifier) in case AppleCare or your tech support division needs them.

System Preferences and Parameters

System Preferences and Parameters


In the end, OnyX is a great, free option for cleaning out the cruft that builds up on your computer from time to time. It is also a great chance to see if you could benefit from other shareware utilities like CleanMyMac or Cocktail – which have easier to understand interfaces and more support should you have any questions.

Definitely give OnyX a shot if you think your Mac is running a bit on the slow side – and let me know if it makes a difference!


A multifunction utility for Mac OS X which allows you to verify the Startup Disk and the structure of its System files, to run misc tasks of system maintenance, to configure some hidden parameters, to delete caches, and to remove a certain number of files and folders that may become cumbersome and more.