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So, your Mac is running out of storage. You try to figure out what’s taking up your disk space by clicking the Apple logo on the top-left of the screen, selecting About This Mac, and hitting the Storage tab.

macOS System Data Taking huge amount of disk
My MacBook Pro “System Data” is taking a large amount of disk space

To your surprise, you see a grey bar “System Data” that seems to occupy way more space than you think it should. In the example above, the System Data takes an astonishing 232 GB of precious storage.

Worse yet, you have no idea what’s included in “System Data” storage, because clicking the “Manage” button brings you to this System Information window… and the “System Data” row is greyed out.

Why does my Mac system require so much space? What does it contain? Is it safe to remove some of those system data files? How do I regain more storage space?

Questions like these may easily get to your head. Although my Mac now has a decent amount of free disk space and I tend not to store large files on my Mac these days, I’m always wary of files that are taking up more space than they should.

I have no idea why “System Data” is greyed out while “Documents,” “Music Creation,” “Trash,” etc. allow you to review the files based on size and type.

My hunch is that Apple does this on purpose to prevent users from deleting system files that could lead to serious issues.

What is System Data on Mac?

During my research, I found many people report that Apple counts application leftovers (e.g. Adobe video cache files), disk images, plugins & extensions in the System Data category.

Since it’s greyed out and we are unable to click on that category for deeper analysis, we’ll have to use a third-party app to assist.

CleanMyMac X is perfect for this kind of analysis. Since I tested the app in our best Mac cleaner review, it immediately came to my head when I saw “System Data” was greyed out in Storage.

Note that CleanMyMac isn’t freeware, but the new “Space Lens” feature is free to use and it allows you to scan your Macintosh HD, and then show you an in-depth overview of what’s taking up disk space on your Mac.

Step 1: Download CleanMyMac and install the app on your Mac. Open it, under “Space Lens” module, first click the yellow “Grant Access” button to allow the app to access your Mac files and then select “Scan” to get started.

Step 2: Soon it’ll show you a folder/file tree and you can hover your cursor over each block (i.e. a folder). There you can find more details. In this case, I clicked “System” folder to continue.

Step 3: The file breakdown below indicates that some Library and iOS Support files are the culprits.

The interesting part is that the System file size shown in CleanMyMac is much smaller than the size shown in System Information. This puzzles me and makes me believe that Apple definitely has counted some other files (not real system files) in the System category.

What are they? I have no clue, honestly. But as reported by other Mac users who experienced the same issue, they said Apple also considers app caches and iTunes backup files as System files.

Out of curiosity, I ran CleanMyMac again for a quick scan. That app found 13.92 GB in iTunes Junk. Further review revealed that the junk files are old iOS device backups, software updates, broken downloads, etc.

But even after adding this amount to the original system files returned by CleanMyMac, the total size is still a bit less than what’s returned in System Information.

If cleaning the System Data is still not enough to bring your Mac’s available disk space to a normal level (i.e. 20% or more), check out the solutions below.

What Else Can I Do to Reduce System Data on Mac?

There are tons of ways out there. Here are a few of my favorites that should help you get back a decent amount of space quickly.

1. Sort all files by size and delete old large files.

Open Finder, go to Recents, and look at the Size column. Click on it to sort all recent files by file size (from large to small). You’ll have a clear overview of what items are eating up a large amount of space, e.g. From 1 GB to 10 GB, and from 100 MB to 1 GB.

On my MacBook Pro, I found a few large videos that could be transferred to an external drive.

Note: If the Size column doesn’t show up, click on the Settings icon and select Arrange By > Size.

2. Delete applications that you don’t use.

In the “System Information” window, I noticed that the “Applications” category was taking 71 GB of disk space. So I clicked on it and in a few seconds, I quickly realized there were quite a few large apps (such as iMovie, GarageBand, Local, Blender, etc) that I don’t use at all or no longer use. Some of these are apps pre-installed by Apple by default.

I have no idea why macOS also counts storage taken by third-party apps into “System Data”, but deleting these apps definitely helps me regain quite some disk space. All you have to do is select the apps and hit the “Delete” button.

3. Clean Trash and other unnecessary files.

In the same “System Information” window, I also found these two categories “Music Creation” and “Trash” were taking 2.37 GB and 5.37 GB. I don’t use GarageBand, I certainly don’t know why “Music Creation” is taking away so much space. So I have no hesitation but to hit the “Remove GarageBand Sound Library” button.

Meanwhile, don’t forget to clean “Trash”. Since macOS doesn’t automatically delete files sent to Trash, it can add up very quickly. However, it’s better to take a closer look at the files in Trash before you hit the “Empty Trash” button.

4. Remove duplicate or similar files.

Last but not least, duplicates and similar files can stack up without you being aware of it. Finding them is sometimes time-consuming. That’s what Gemini 2 is designed for. Simply select a few frequently used folders (e.g. Documents, Downloads, etc.) in the main zone of Gemini.

It then scans them and returns all the duplicate files that might be worth removing. Of course, it’s always a good practice to review them before doing so. You can also read more from our detailed Gemini review here.

Wrapping It Up

Ever since Apple introduced the Optimized Storage feature, Mac users got the option of saving space by storing content in the cloud. Apple also has several new tools that make it easy to find and remove unneeded files.

That bar under the Storage tab is beautiful. It does allow you to get a quick overview of what’s taking up the most space on our hard drive. However, it still lacks insights into the “System Data” category as it’s greyed out.

Hopefully, the guides above have helped you figure out the reasons you’ve got so much system data, and most importantly you’ve reclaimed some disk space — especially for new MacBooks pre-installed with flash storage — every gigabyte is precious!