How to Clean Your Mac When “System” Storage Takes Too Much Space

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.

To your surprise, you see a yellow bar representing "System" that seems to occupy way more space than you think it should. In the example above, it only shows 33.87 GB, but take a look at this Apple discussion — some Mac users report that System Storage takes an astonishing 250 GB.

Worse yet, you have no idea what's included in "System" storage, because clicking the "Manage" button brings you to this System Information window… and the "System" 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 files?

How do I regain more storage space?

Questions like these may easily get to your head. Although my Mac now has a good amount of disk space available, I'm always wary of files that are taking up more space than they should.

I have no idea why "System" is greyed out while "Documents," "System Junk," "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 Files Are Included in System Storage on Mac?

During my research, I found many people report that Apple counts iTunes backup files and app caches (e.g. Adobe video cache files) in the System 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.

DaisyDisk is perfect for this kind of analysis. Since I tested this app and mentioned it in our best Mac cleaner software review, it immediately came to my head when I saw "System" was greyed out in Storage.

Note that DaisyDisk isn't freeware, but it offers a test drive mode which allows you to scan your Macintosh HD. It then shows you an in-depth overview of what's taking up disk space on your Mac.

Step 1: Download DaisyDisk and install the app. Open it, and click the white "Scan" button to get started.

Step 2: Soon it'll show you a sunburst diagram. You can hover your cursor over each block. It will blink, and details about that block will show up. In this case, click "System" to continue.

Step 3: The file breakdown below indicates that Library files are the culprits.

The interesting part is that the System file size shown in DaisyDisk (7.5 GB) is much smaller than the size shown in System Information (33.87 GB). 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 3 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 DaisyDisk, the total size is still a bit less than what's returned in System Information.

If cleaning the System Storage is still not enough to bring your Mac available disk space to a normal level (i.e. 20% or more), see below.

What Else Can I Do to Reclaim More Disk Space?

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.

In 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: Run CleanMyMac 3.

If you are not a power Mac user, another way to help you quickly locate unnecessary files is using CleanMyMac, an app that won our award for the best Mac cleaner software. As you can also see in my detailed review here, I believe CleanMyMac is a must-have app for all basic users.

#3: Remove duplicate files with Gemini 2.

Don't forget those duplicates and similar files! They 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 my Gemini review here.

Wrapping It Up

Ever since Apple introduced the Optimized Storage feature on macOS Sierra and High Sierra, 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 on the "System" 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 (usually 128 GB or 256 GB) — the storage is so precious!

  • JP
  • January 29, 2018
JP
 

I'm JP, the founder of this blog. I've been passionate about computer software ever since I had my first laptop in 2007. I currently use a Macbook Pro, a PC (HP Pavilion), an iPhone & iPad, and an Android phone. My goal is to provide you with useful software and how-to tips to solve tech related issues. Learn more about me.

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