Why are my macOS system files huge? (Over 400gb)

My iMac has roughly 780gb in total and is running out of space (1TB partitioned for Windows using Bootcamp). I saw in 'About This Mac' that my system files are taking up 421gb while my actual documents and files are using only 388gb. I went into 'System Information' on my iMac to see if there was a way I could delete any of these, but 'System' is grayed out.

I used ncdu to try and find the files taking up so much space, but tells me that the hard drive has 388gb of files, and does not include the system files. How do I find the system file/files taking up all the disk space?

Also, I do not have time machine turned on. Using MacOS High Sierra on an iMac from mid 2010.

KeeperOfKale

Posted 2018-05-16T23:11:13.897

Reputation: 141

Do you have iTunes, iPhotos and iBooks stored on your system? I believe iTunes and iPhotos would count as documents, but e-books stored in iBooks are stored somewhere in the ~/Library/ directory as explained here. Also, your ~/Library/Application Support directory can balloon as well. That is where your iDevice backups are stored and that can take up tons of space as well.

– JakeGould – 2018-05-16T23:29:25.743

I would recommend also running Onyx at least once to clear out system caches and see what’s happening.

– JakeGould – 2018-05-16T23:29:55.937

Make sure to run Disk Utility and do a verify/repair of your disk. If a filesystem’s data structures become corrupted, it can think files are far bigger than they are. Fixing filesystem corruption has been known to clear up inexplicable disk space usage in the past. – Spiff – 2018-05-17T06:10:16.153

There's a canonical QA for this on Ask Different - https://apple.stackexchange.com/questions/5353/how-can-i-figure-out-whats-slowly-eating-my-hd-space

– Tetsujin – 2018-05-17T09:12:42.583

Possible duplicate of Mac OS Sierra and High Sierra occupies 95GB on my MacBook Pro 2017 128GB Edition. How to Clean?

– Melebius – 2018-05-22T05:47:10.360

I'm voting to close this question as off-topic because it is answered in a canonical question on the Think Different SE site: https://apple.stackexchange.com/questions/5353/how-can-i-figure-out-whats-slowly-eating-my-hd-space

– music2myear – 2018-05-25T22:46:10.223

Answers

I like to use CleanMyMac 3.app to take a look at my disk usage and help me clean up any disk space that could be reclaimed.

This includes unused language files in the system, huge system log files that need to be trimmed/rotate/deleted, user cache files, mail attachments, left over iPhoto junk, left over iTunes junk, empty trash bins, large and old files that may not be needed any more, etc....

It can also help remove things left behind when you just dragged a file to the trashcan and didn't remove all the other files that might be associated with it but are in other directories.

DaisyDisk is another good tool for helping you to visualize how much disk space is being taken up by what kinds of files.

Hope that helps!

Brad Knowles

Posted 2018-05-16T23:11:13.897

Reputation: 124

1Just commenting to let everyone know that Clean My Mac will only work for free for the first 500mb it cleans, which was pretty disappointing for me. – rpivovar – 2019-03-07T15:48:11.107

I tend to use grand perspective to figure out what is going on when I run out of space. It gives a nice visual and you can open the file locations.

After installation, run the program > Select a folder to scan (you'll want Macintosh HD) > Wait for the visual to pop up. The huge squares are the space hogs. If there is a cluster of a similar color, they may also be taking space. Then, right click and open their locations in finder to figure out the folder system. One thing, give it a lot of time when you do the scan, it will take a while.

Overview from site:

GrandPerspective is a small utility application for Mac that graphically shows the disk usage within a file system. It can help you to manage your disk, as you can easily spot which files and folders take up the most space. It uses a so called tree map for visualisation. Each file is shown as a rectangle with an area proportional to the file's size. Files in the same folder appear together, but their placement is otherwise arbitrary.

Talos Potential

Posted 2018-05-16T23:11:13.897

Reputation: 131

Please read how to recommend software in answers, particularly the bits in bold; then edit your answer to follow the guidelines there. Thanks!

– bertieb – 2018-06-26T23:52:43.407

The problem for me was a deleted user account folder that was retained. In my case, the folder was called Macintosh HD/tim (deleted).

David Hariri

Posted 2018-05-16T23:11:13.897

Reputation: 101

Might want to check mail logging - may have massive useless connection log files.

 ⁨Library⁩ ▸ ⁨Containers⁩ ▸ ⁨com.apple.mail⁩ ▸ ⁨Data⁩ ▸ ⁨Library⁩ ▸ ⁨Logs⁩

Turn off mail connection logging: https://apple.stackexchange.com/questions/223390/huge-apple-mail-logs-connection-logging-enabled

I just free'd up over 650Gb of space by removing the log files and turning off connection logging. Not sure why it was on in the first place!

smuskal

Posted 2018-05-16T23:11:13.897

Reputation: 1