SYSTEM DATA - excessive

I suggest you look into the GrandPerspective app. This does not delete files on its own, but gives you an easy way identify very large files that may be contributing to your System Data. It is true that your System is in locked location and untouchable, but files can be added to your ~/Library/ folder.

https://grandperspectiv.sourceforge.net

I also suggest removing all cleaner apps that you have installed by first running the installer supplied by the app and then following up by running EtreCheck to make sure all files are removed. CleanMyMac is one such cleaner that borders on being Malware and will cause problems with your system. More information on these cleaners can be viewed in this Support discussion.

Should I use a utility such as MacBooster… - Apple Community

After the cleaners are removed, you can post your EtreCheck report here using the "Additional Text" option when posting, so the full report will be seen. I suggest just the one time free scan and there is no need for it to be used on every launch.

https://etrecheck.com/en/index.html

The locations you will want to look for excessive file sizes using GrandPerspective are:

• Downloads folder
• Documents folder
• Desktop folder
• ~/Library/Application Support
• ~/Library/ScreenRecordings
• Review the "iCloud Drive (Archive)" folder in your Home folder, if you have one, for documents that were stored and no longer needed.

There are other locations, but that should give you a start. You may need to boot into Safe Mode to remove files from you Library folder. It is always best to make sure you have a backup before deleting any of these files and feel free to ask if you are unsure. Also review if you have any other Users added by looking in your settings.

Manage Storage

It is generally a good computer practice to alway keep at least 15% to 20% of the Total Drive Capacity’s as Empty Space. Allowing the computer to drop below these guidelines may eventually, cause unintended consequences.

➡️ This computer appears to have plenty of Empty Space and is in not danger of running below the suggest guidelines for Empty Space ⬅️

There is Purgeable Space and there is Empty Space.

Purgeable Space which is Controlled by the Operating System. When the Operating Systems decides the computer needs additional Empty Space, it will move a portion of the Purgeable to Empty space

AFAIK - there is no User Actions to hasten this transition from Purgeable to Empty Space

It can day or longer before this will occur  

The links below will assist in identifying what is taking up space on the Internal Drive and provide possible ways to remove data that is under the direct control of the User ( Home Folder ) . 

Rebuild the Spotlight index on your Mac

What is “Other” storage on a Mac, and how can I clean it out?

Free up storage space on your Mac

OmniDiskSweeper Safe to use

GrandPerspective 

How to delete Time Machine snapshots on your Mac.  

Often caused if the Time Machine Drive has not been attached  to the computer and TM Backup is set to run on a Schedule. 

TM Backup will make Snap Shot on the Internal Drive awaiting the TM Backup Drive to be attached. 

Only then will the Snaps Shots be transferred to the External Drive and deleted the Internal Drive.

See used and available storage space on your Mac

Locate backups of your iPhone, iPad, and iPod touch

Notation - If the user is using a cloning software like Carbon Copy Cloner - suggest tweaking the Safety Net Feature in this software. It may be making additional Snap Shots that are not being Cloned to the Eternal Drive. If this should be the case, these Snap Shot could be using additional space on the drive 

The final word from Apple on Managing the " Other/ System Data “ Category

Other / System Data: Contains files that don’t fall into the categories listed here. This category primarily includes files and data used by the system, such as log files, caches, VM files, and other runtime system resources. Also included are temporary files, fonts, app support files, and plug-ins. You can't manage the contents of this category. The contents are managed by macOS, and the category varies in size depending on the current state of your Mac.

Form informational purposes Only

Part 1 of 2

In macOS 11 Big Sur, macOS 12 Monterey and macOS 13 Ventura. 

The Operating System resides in a Sealed and Read Only Volume that can not be opened by the User nor by Third Party Applications.

The only Entity that can open and modify or alter this Volume is Apple.

That would occur when a update or UpGrade is performed.

Part 2 of 2

Apple has already answered that question

Other / System Data: Contains files that don’t fall into the categories listed here. This category primarily includes files and data used by the system, such as log files, caches, VM files, and other runtime system resources. Also included are temporary files, fonts, app support files, and plug-ins. You can't manage the contents of this category. The contents are managed by macOS, and the category varies in size depending on the current state of your Mac.

Many good points by learned colleague above

FYI as comparison Only

Have 2 M1 Machines each with the 252 GB SSD drives and each started with macOS 11 BigSur. Each has been upGraded to macOS 12 Monterey and presently sitting on Ventura 13.4

Each machine is using about 31 GB of the 251 Drive Capacity

The Third M2 Machine came with Ventura 13.0 and updated to 13.4 Ventura. The Drive, this time I anticipated Growth Needs and choose the 500 GB SSD

Right now sitting with about 32 GB used of the 500 GB Drive

The Last machine from 2011 is stuck on High Sierra macO 10.13. Flipped the Fusion Drive out for a 500 GB SSD ( performance reasons ) - It is using about 28 - 29 GB of the 500 GB Drive

Management, as I understand the term in general, is make due with what is available not with what one wants.

Disk Cleaners by any name of brand

Any of the below should be removed as per Developers Instructions

1 - Disk Cleaner 

This will include CleanMyMac , aka “ BrickMyMac “

MacKeeper,

Dr Cleaner Pro Plus

Open Cleaner one Pro

Macmechanic

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

The original poster complained of excessive System Data, so the only relevant part of this is about System Data: "You can't manage the contents of this category". So what is the original poster to do? I have 400GB of System Data and have the same apparently insoluble problem, like many other people. There appear to be no utilities that can help (I have tried OnyX, Mac Cleaner Pro, OmniDisk Sweeper, Daisy Disk, CleanMyMac X, Parallel Toolbox, DiskGeeker, MacBooster 8, among others) - it seems Apple is correct that nothing can be done. Other than buying a new computer with more SSD?

Anthony Glaser wrote:

The original poster complained of excessive System Data

There are many such complaints.

so the only relevant part of this is about System Data: "You can't manage the contents of this category". So what is the original poster to do?

Provide additional information? Screenshots? Follow up with people who try to help?

I have 400GB of System Data and have the same apparently insoluble problem, like many other people. There appear to be no utilities that can help (I have tried OnyX, Mac Cleaner Pro, OmniDisk Sweeper, Daisy Disk, CleanMyMac X, Parallel Toolbox, DiskGeeker, MacBooster 8, among others) - it seems Apple is correct that nothing can be done.

Who ever said that Apple said "nothing can be done"? The most likely cause of this problem is using those kinds of 3rd party apps.

Other than buying a new computer with more SSD?

You mean, other than the solution?

Because ultimately, that's the problem here. People run out of disk space. These problem always spike after releases an operating system update. Those are big updates that need about 10 GB of free space to download and install. And because people are literally addicted to these updates, they freak out when they can't apply one. So they download as many 3rd party "clean up" tool as will fit in that 9 GB of free space they have.

They run all those tools, only to end up with even less free disk space than they had before. At this point the freaking out is so severe that they post a message here.

But then, the system clean-up daemons run overnight and they mysteriously have 120 GB free the next day from all those files they deleted. So they can apply the update and deal with lingering problems from those "clean up" apps for years to come. But they often don't come back here to follow up. They do sometimes. That's how we know what's going on.

But the problem really is a hard drive that is too small. There are plenty of posts from people who have found even worse solutions, like spending $4000 for the fastest SSD ever made, but saving $500 to get a tiny amount of storage on said SSD. Then they spend $400 for a bigger, but much slower SSD, and try to configure that as a boot drive.

It's really a pretty simple problem. Delete files. Buy a bigger SSD. People who do that simply don't ever have this problem.

Sunsh1neC0ast - Yesterday I started an online chat session with Apple about this, and within 5 minutes I was set up with a senior tech support guy who spent an hour and a half with me on line, holding my hand through a large number of (to me) complicated steps that I do not really understand, with the net result that my System Data has dropped from 400 to 41 GB, so I am very happy. He said anyone with this problem should reach out to Apple as there is no app, utility, or other ready-made answer, as every case will be individual. We still don't know quite what caused my System Data to get so huge, but at least (for the time being) the problem is solved. By the way, I do not have Apple Care and my 2021 MacBook Pro is of course long out of warranty

I use the paid version of Daisy Disk to reduce Purgeable. Never fails to work.

For me, it reduced Purgeable, just as pretty much every other similar utility did - but that was only about 3GB, and it did nothing for the 350GB of junk in System Data