System data taking 155gb on Sonoma macOS

You can use disk space visualizer programs, such as Disk Drill (tiles - a free option in this program), and DaisyDisk (shareware), to search for large files and folders on your disk. Many programs leave behind garbage and hidden folders.

For me, the strangest discovery was finding a large .Trash hidden folder in the system subfolders under /var/ (left over from a deleted user) and a 22-gigabyte cache file from the Telegram messenger.

System Data used to be called Other Category on earlier systems. The Other category is a potpourri of files which can include:

• System temporary files

• macOS system folders

• Archives and disk images (.zip, .iso, etc. - often found in the Downloads folder)

• Personal user data

• Files from the user’s library (Application Support, iCloud files, screensavers, etc.)

• Cache files: browser, Mail

• Mail messages & attachments

• Fonts, plugins, extensions

• Safari reading list

• iTunes backups

• Crud resulting from jailbreaking your iDevice

• Game data

• Saved data files

• Call history

• Notes

• Media

• Voice memos

• Other files that are not recognized by a Spotlight search

• Media files that cannot be classified by Spotlight as a media file because they are located inside of a package

• Files created and modified by other user accounts on your Mac.

They can be located anywhere on your hard drive.

The files that you have control over are located in the Documents, Downloads, Pictures, Music and Movies folders.  You can use this free app, GrandPerspective, to find the largest files on your drive so you can determine if they can be deleted or moved to an external HD for storage.

Note: you can empty the Downloads folder after the apps and/or updates that were downloaded have been installed or applied.  Some users have found a couple of Gigabytes of files in their Downloads folder which are no longer needed. 

Also do this: boot into Safe Mode according to How to use safe mode on your Mac and test to see if the problem persists. Reboot normally and test again.

NOTE 1: Safe Mode boot can take up to 3 - 5 minutes as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files

NOTE 2: if you have a wireless keyboard with rechargeable batteries connect it with its charging cable before booting into Safe Mode. This makes it act as a wired keyboard as will insure a successful boot into Safe Mode.

Ondashek,

CMM is considered malware by most experienced users. It does absolutely nothing to enhance Mac OS and does nothing that Mac OS cannot already do. I (and many other experienced users) recommend locating CMM's uninstall instructions and following them to the letter.

Only download third party:

• Cleaning apps
• Antivirus apps
• Security apps
• VPN apps

if you want to have a slow, unstable and feature rich (in a bad way) experience with Mac OS.

Mine using 760GB System Data.

Thank you. What is surprising is that it was "clean" before updating which makes me think it's related to the upgrade to Sonoma

DO NOT INSTALL OR USE CLEANMYMAC! As you're already been told it's considered to be akin to malware by most here.

I had to be pretty brutal with my iCloud Drive and pare storage shared on my MacMini given space available. Most was detached from iCloud sharing so almost nothing is shared to local storage. I just download as necessary, manually and manually upload. As a result, do not get shared using space any more.

Hope this is a clue so you'll be able to implement what settings you prefer. Use of iCloud in this manner is a bit tricky. My space is now pretty stable. The Mini balks badly in Sonoma when at free space below 90GB, FYI.

Are you using iCloud Drive?

In Finder>Go Menu>Go to Folder, paste this in & pres Enter...

./Library/Application Support/CloudDocs/session/

What do you see in there???

What size is that folder?

Disk Cleaner is unnecessary and Parallels "Free Memory" I am not familiar with. However after reading up on it a bit if you are using Parallels to run Windows on you Mac just leave it. However if you are not then uninstall.

What I believe you need to do is to move large libraries such as photos, music and movies onto an external HD. Then re-index Spotlight. Don't be concerned so much about how much is showing on that graphic. It is designed to only be a rough guide and not a "this has to be exact" item.

Me too, but I don't think it's just Sonoma. I loaded Sonoma on my older I-Mac and there wasn't a problem with data storage. The clock stopped updating on that machine so I got a newer model. When the data was migrated to that computer it took up considerably more storage space! The system is taking up about 87 G and the System itself takes up about another 20 G. Aside from this very large chunk of computer memory which I evidently cannot modify, I wonder why the documents also seem to be taking up more memory.

I am dismayed with the push to gather advertising data from customers and do not want to store files on the Cloud for them to mine that data as well! Apple needs to fix the storage problem ASAP.

I had this issue as well, and connecting external hard drives suddenly cut the data more than in half. I had 45 gigabyte left on my drive, after connecting three external SSD's I suddenly have 102 gigabytes of space available.

my system data above 180Gb on sonoma Mac OS. out of 256 gb 180gb is occupying for system data and 20 gb is for Mac OS .

According to your graphic Mac OS is taking 18GB

Do you regularly shutdown your iMac or do you leave it running all the time. Regular restarts are good for housekeeping.