Why does the system use 150 GB of storage?

i had this problem too, and i reached out to apple support:

Normally system storage is that which is stored in the library of the Mac.

The next thing to do will be to clear all Caches. Caches are like bookmarks. Where it allows you to find sites or files faster. Caches does the same thing for applications.
Caches are stored in the hard drive and not on the memory. However, Caches run from the Memory and impact the performance on it. This will not impact or delete any personal information.

To do that I will need you to go to Finder. Once in Finder, on the top left hand corner of your display there is an dropdown option named “GO”. Please click on there.
On your keyboard please hold down your OPTION key.
The library folder should populate in the dropdown you had selected. Please select the folder named LIBRARY.
Once in the library please click on the CACHES folder and delete everything in there.

Now that this is done Open Finder and select the “Go” menu at the top of the screen. In the drop down, select “Home”

With the Home folder option, switch to List View (Command-2) and open “Show View Options” from the View menu (Command-J)

Place a check in the checkbox for “Calculate all sizes”. You should start seeing each folder calculate the size in Finder. The bigger ones may take longer

This will help you determine what folder is using the most data. Next, go back to the “Go” menu in the menu bar at the top of the screen.

With the “Go” menu open, hold the Option key down and click “Library” when it appears.

With the Library open, pull up the View Options menu (Command-J) and place a check in the checkbox for “Calculate all sizes”. Check what is using the most space. Application Support may be taking up a lot of space if multiple 3rd party applications are installed.Check each folder and subfolders within Users to see the culprit of what is using the most Space. deleting the whole folder will be just fine as long as you are confident you don’t use or have deleted them.Any application that you don’t use will be fine to delete as that won’t impact the performance on your Mac or the Apps.

The Containers folder categorize is normally created by third party programs that are made to scan the computer. Certainly not pertaining to the Mac, I would suggest to erase it.

I was able to clear up 84 GB with these tips. Also - be sure to erase iMessages in that folder because that was where my bulk was.

I have a late 2015 iMac at work with the same problem. But it's no mere 100-150 GB of "system storage," it is a whooping 800 GB of my TB hard drive.

I work with some big files from time to time, but I am rigorous about cleaning up my folders and desktop, I don't have any music or videos, and the only software I really run is the most recent version of Adobe CC (I don't even use the cloud features or Adobe library!). So i'm not buying this "that's a normal amount of usage" because 800 GB is not normal and even after cleaning the majority of my work off the computer, it hasn't gone down.

I would seriously appreciate some help from Apple on this issue. (I'll post again if I find a solution myself)

So evidently the solution to this problem is to leave it alone? All I did was work from my laptop until about lunchtime and now suddenly I check the storage:

What's the answer here? Is the system just temporary memory? I'm still not thrilled about losing 99 GB of storage space, but it's better than 800 GB. You can see from comparing the screen shots I did delete about 3 GB of pictures and 10 GB of junk from the downloads folder, but that wouldn't account for 699 GB of "system" storage.

How can I prevent this from occurring? Do I just ignore all the alerts that indicates storage is running low and carry on until it resolves itself every time? To me it seems to be a bug/delay in the software's ability to read what is "free" versus "used" space, and then anything still pending it identifies as "other" and puts it down as "system usage."

I'm glad I didn't waste $10 on DaisyDisk.

Hello, i just got same problem when i updated my Macbook Pro 15" Mid-2015 to MacOS High Sierra just today. System folder just hits up tp 75 GB+ and i really don't know why. I have windows 10 alongside macOS with bootcamp which is about 100 gb, and left space for 150 GB to macOS. I also checked it with OmniDiskSweeper and it only shows 70 GB of used space, 150-70 = 80 GB, and system is 75 GB, so there must be only 5 GB left for me but it is 38 GB. I will also upload a photo but i checked every thread about this problem, still found nothing. Any help will be appreciated.

Just an update to the high reported System size issue, I've noticed since installing iTunes 12.6 (not sure which version it was, two released in a sort time of each other) my high reported System size has returned to normal (and identical to that reported under Finder). The iTunes section has subsequently increased by a corresponding amount. So it looks like sizes reported under System Information bar graph/table are now similar to those reported in Finder for the various sections, on my setup anyhow.

Yes, particularly @MacKeeper. They take your money and destroy your system. I had to have Apple help me for an entire day. If you download Mac Keeper, then you need the only adware uninstaller @Apple endorses @Malwarebytes

I can't answer why the "system" is using 150Gb in your case, but I can say that I spent a lot of time gradually moving "my" stuff to iCloud. In my case, over years my system disk has almost filled numerous times. Recently, I was not able to complete the installation of all parts of Xcode 8.3.1. Recent investigation led me to realize my system disk's System folder has grown to more than 200Gb--not good for a drive with only 256Gb capacity! On another, newer Macintosh, its System folder shows, via a command-I, only 7,923,185,340 bytes (5.17 GB on disk) for 160,935 items. Same operating system, but a vastly different history of use. So clearly, not all unneeded files are being removed when either a system update or an Xcode update are applied (or maybe even both). It seems to me that to figure out which are not needed would be a formidable task to anyone not knowledgeable of the update software. My fix will likely have to be new hardware--to Apple's delight.

Not sure you can fix this issue if it's down to the "process" incorrectly allocating and showing usage, that will be for Apple to resolve in future updates of either the OS and/or the program behind the problem.

I had System constantly reporting 70Gb higher than I thought it should have been and iTunes only reporting for Apps and Podcasts, no indication of my music size, which just happened to be 70Gb - so concluded music (mp3's) size was being allocated to System for some unknown reason!

Nothing I tried short of deleting the mp3's reduced System size, but when added back System increased back to it's previous figure - just gave up in the end. When Apple released the latest iTunes I noticed this issue was corrected, whether it was coincidental I'm not sure, but System dropped by 70Gb with iTunes increasing by the same amount.

Now why all this was going on Finder was always reporting what I had expected, System and Library folders of normal size and more importantly the Music folder of 77Gb (what it's always been) so I've always concluded it was just down to misreporting of the new Storage/Manage process (like yourself).

Some have reported even though having music and photos kept on external drives (to save space on the internal), this new reporting system still showed the size as though the files were still kept internally, in some cases reporting total usage higher than the internal drive size itself!

If you can use Finder to confirm that you do not have any large chunks of disk space being unknowingly taken up then I would leave it at that, appears Apple could still have some fine tuning to do with this new reporting method.

Hi

I found I was regulary dumping things with drag & drop on the Desktop. For example a memorystick with fotos. This is accounted for as system space.

After I deleted those the systemspace recovered again. Also a reboot released some locked big files within the MacOs.

Just my 2 cents,

regards

Since my development work was stalled, I bought a MacPro to do the work of my MacMini, i.e., so I could install the new version of Xcode. Then, after the MacPo's delivery, I did more reading and came across insightful comments and solutions on stackoverflow.com. I also bought DaisyDisk, which was extraordinarily helpful in navigating to the main source of my particular problem. I have been developing for iOS since iOS 5.0. Xcode keeps lots of data about each application uploaded to iTunes for each available device and released iOS version. Ridding myself of the files recommended on stackoverflow.com via Terminal, erased about 60Gb under my Users directory in a few seconds. "Magically", the System folder shrunk by the same amount.

If I'd first bought DaisyDisk and read a little more on-line, I might have saved $3,500. (But then again, I'd been ******* for the MacPro for four years anyway, so am not complaining.)

I saw same problem because i use core dump which store core files when an app crash, check in your folder /cores, if you see a lot of files, follow the post below, which will solve the problem:

https://blog.liplex.de/disable-core-file-dumps-on-mac/

I assume this 150GB is the space used on your dystem drive - that includes ghe dystem plus all your documents, images, videos, etc. 150GB is not all that much.

The real question is how much it was using before.

I have not seen the used space grow significantly by the mere fact of upgrading to Sierra.

If that is what you are seeing then it desrrves being looked at more thoroughly.

But whatever you do DON'T fall for the trap of those "cleaning" programs that claim to regain space by freeing your mac from "junk". Thry are scams and will seriously damage your system.

El Capitan should still be available in the Mac app store.

The space used might have grown if you were having a big iPhoto Library... Sierra does not have iPhoto but Photos which uses a 'Photos Library' distinct from iPhoto

150GB ain't that big unless you know what it was previously.