System Data is out of control.

Not exactly sure what is going on with your Mac. System primarily includes files and data used by the system, such as log files, caches, VM files, and other runtime system resources. It also includes temporary files, fonts, app support files, and plug-ins. Spotlight also uses this space.

FWIW. The "Other" category was renamed to "System Data" starting with macOS Monterey.

One thing I can think of is to avoid using 3rd-party "cleaner" apps. These tend to cause more issues that resolve them, and we get numerous posts here with folks asking for assistance with issue that turn out to be the result of using them.

Lastly, have you considered, completely erasing your system drive, and installing a "clean" copy of macOS ... and then, after you confirm that "System Data" is now more manageble, restoring your data from a backup?

Here are two simple things to try:

1) Restart in Safe Mode, log in to your account, then restart again normally and see how much space, if any, you gained

2) In Finder, press Command-Shift-G and paste

~/Library/Caches

Drag everything in there to the trash, and empty it.

Restart.

One of the primary "users" of System Storage on your Mac is Time Machine ... especially if you do not have a dedicated TM backup drive connected ... either directly or on the local network. When this is the case, TM will create local snapshots. In theory, they are dynamically removed ... but this may not always be the case.

Ref: About Time Machine local snapshots - Apple Support

You may also check the overall Library:

/Library/Caches

and see how big that one is.

On my mac, the one under ~/Library was 4 GB, and the one under /Library was 10 GB, nothing out of the ordinary, but some times a cache file or log file can grow out of proportion.

You may check the sizes of those, and of /Library/Logs, ~/Library/Logs and possibly other folder there and try to find out where some uncommonly large folder is - that may guide to the right place.

Part 1 of 2

Two cent here

User wrote "I've purchased CleanMyMacX and run it several times "

Any Third Party Applications that will interfere with the normal operation of the OS,  is an invitation for disaster and comprise the Operating System

Certain Applications maybe available on the Apple Apps Store - this only means the Developer is prepared to pay Apple a portion on each sale. What the Application may do to the computer is up to the User to check this out before purchase

Any of the below should be removed as per Developers Instructions 

1 - Disk Cleaner 

This will include CleanMyMac aka " BrickMyMac "

Read some of the posting and arrive at your own conclusions.

Part 2 of 2

Specific to CMM aka CleanMyMac >> aka " BrickMyMac "

The steps in #1 below is predicated on the Offending  Application has been Removed as per the Developers Specific Instruction 

# 1 Some Contributors suggest restarting in Recovery Mode and choosing to Reinstall the Operating System over  the existing installation. 

This may or may not replace elements of the Entire Operating System including the Home Folder ( User Account )  and replace any corrupted or removed elements of the Operating System and make thing right.

#2 - Then there are Other Contributors ( like myself ) would suggest  from this link Use Disk Utility to erase a Mac with Apple silicon.

For Intel computer >> Use Disk Utility to erase an Intel-based Mac followed by How to reinstall macOS

Thereafter to start from scratch and install all Required Application directly from the Apple Apps Store or Directly from the Developer.

If going this route - I suggest Not using Startup Assist to migrate things back as this will probably Re-Introduce the existing  issue that existed when the TM Backup was made 

Would suggest Only Migrating the User Account and nothing more.

Issues that may have existed when the TM Backup was made would be migrated to the New Installation.

This would badly pollute the new Original & Pristine installation and reintroduce the Original Issues

The simplest way to remove existing snapshots is to change TM's backup setting (temporarily) to "Manual." The steps to do so, are in that support article I provided you.

It's provided in the section, titled: How local snapshots use storage space

From my experience, it takes approximately 10-15 mins.

You can always check to see if any snapshots are still on your Mac with this command in the Terminal:

• sudo tmutil listlocalsnapshots /

but only 4 are listed.

There are 5 volumes ... Macintosh HD, Macintosh HD-Data, VM, Preboot & Recovery.

VM, Preboot & Recovery are hidden volumes that are not visible in left pane in Disk Utility

The thing about really starting fresh is that you should really only migrate back your accounts.

FWIW, I don't think that migration brings back all the caches (and perhaps system logs), as they are transient things.

FanDead wrote:

I hadn't thought of that, but considering i backup to a 4TB external SSD, I doubt it.

... unless that external drive is NOT attached, and TM runs a backup ... which it will do hourly.