System Data taking up 820GB of storage

Do you expect that you only have that little amount of documents and photos?

It could just be your data that Spotlight failed to categorize correctly because the index is corrupt. Try rebuilding you Spotlight Index.

johnjdd wrote:

what the title says. The app "Disk Space Analyzer" doesn't show this to full extent, which is why I can't find out what's the issue here.

Normally I would recommend one of those "Disk Space Analyzer" tools. However, if you've already used one and it isn't helping, maybe try a different one. I just checked on the Mac App Store and there are several. But perhaps they don't do a very good job, or they aren't aware of the limitations of the Mac App Store.

This "System Data" is actually just "other data" that can't be categorized as "documents", "images", "movies", PDFs, etc. It is one of the following:

• Local snapshots - You can check this in Disk Utility. Show All Devices. Show APFS snapshots.
• Other user accounts - There is no way to visualize or categorize files that you don't have permissions to see.
• Something else - This is just other data that the Storage display can't categorize. It can be some 3rd party app, or an Apple app, that has lost its mind and is creating some massive database. I would think that a 3rd party storage tool would show you where this was. But I can't vouch for other people's apps. And I'm not allowed to post a link to my own app here in the forums.

johnjdd wrote:

No, iCloud is intensively used and there are no personal documents at all saved on the SSD itself.

Also, this would be shown as „Documents“ and not as „System Data“.

The System - Data Volume comprises more that what is contained in the Document folder 

System Data: Contains files not listed here. It includes system files like log files, caches, VM files, and runtime resources. Temporary files, fonts, app support files, and plug-ins are also included.

It can also comprise Time Machine Backup Snapshots awaiting  transferred to the Destination Drive 

It can comprise IOS Backup 

Also, other User account used on this computer plus User Accounts that have since been Removed but the User Home folder was left behind 

To get a more complete picture of the files that are consuming space us the GrandPerspective

Please and this is meant in a friendly term.

Help us reconcile " iCloud is intensively used " with what has been presented earlier

This seems to indicate, iCloud is not in Use

Screen Shot with iCloud Turned ON

Can we assume you have tried shutting down, removing power for a few minutes from your Mac and then rebooting? Can we assume you have rebooted into Safe Mode which performs certain maintenance tasks including emptying of caches, then tested again? Has the performance of your Mac been affected negatively?

Obviously that number is erroneous unless you are running near the ragged edge of your storage capacity.

You might want to check under your user directory a folder labeled "Share". I found a ton of relocated folders under that dating back several years that I deleted and picked up another 2-3GB of space.

I'm seeing the same thing on macOS 15.2... more and more storage allocated to System Data as time goes by. While watching this and taking no action on the computer, I too, have seen the amount of storage allocated to System Data both increase and decrease, but it's mostly increasing. I've disabled Spotlight indexing, which has had no impact on System Data growing. Some storage is reclaimed after doing a Time Machine backup, but only few GB. While both of these have been suggested as a possible root cause, at least in my case, neither seem to be the reason for the massive accumulation of storage categorized as System Data. At around 250GB, I'll restart the computer, and then it goes back to around 70GB. I have to repeat this every 5 - 6 days to prevent running out of free space on my drive.

Let us guess

The user doesn't use or what to use iCloud ?

As denoted in below image

Would that be correct ?

Use iCloud Drive on iCloud.com

That is really good news and you have gained an additional 500 GB of space ?

Good work there 👍