MacOS Sequoia filling up with system data

After updating my system, I always shutdown, then startup in Safe Mode. I had a fair amount, not super large amounts of System Data like some of you and after starting up in Safe Mode, then restarting it was significantly reduced. After updating to Mac OS 15.2 release candidate beta I had over 10 GB of Apple Intelligence in the Info button next to Mac OS in System Settings/Storage. This was reduced to 5.8 GB on my MacBook Pro M1 14 inch after starting in Safe Mode, then restarting normally. I would give it a try.

I'm having this problem too! I spent an hour plus on the phone with Apple Tech Support last month. The fix we stumbled upon was to boot into Safe Mode. After booting into Safe Mode, my System Data shrunk from 365GB to 45GBs. I switched my Time Machine backup schedule from daily to weekly thinking that was the culprit, but I'm still having to boot into Safe Mode every 1-2 weeks to shrink my System Data.

Have noticed this on 3 different computers, all running latest Sequoia 15.2 (iMac 27" 2020, MacBook Pro 16" M2 Max, and MacBook Pro 14" M3 Pro). Even with internet off, so no connection and at all and all Apps closed off so nothing is "running", I can sit and watch the drive space disappear. Have tried safe boot on all 3 computers, but even in safe boot on all 3 you can sit there and watch the space disappear in front of your eyes. Albeit in small "MB's" amount (may only be 1-2MB at a time), but it will keep disappearing.

In a 10 minute space I saw it go down from available space of 657.78GB available to 657.55GB (it just went down to 657.54GB as I typed the above) available.

Only just upgraded one of the laptops to Sequoia yesterday which was when I started noticing it more. Then looked at the others to see as well. Very strange.

Have you used Activity Monitor to discover what is actually eating up the space?

Spotlight or more precisely mds_stores was writing huge amounts of almost 100 GB per day. Strangely they never physically appeared on my drive as though they were being deleted instantly.

Since completely disabling Spotlight in System Preferences the amount of "background" writes has dropped below 10 GB per day.

For me, Spotlight index is the culprit. I followed this article and reclaimed ~400GB of space.

It seems that the hidden Spotlight index folder which does not report its size to Finder is consuming excessive amount of space.

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I had the humongous System Data issue about a week ago (90MB of free space?!) and solved by 2 actions:

First deleting the offending cache* at ~/Library/Containers/com.apple.mediaanalysisd/Data/Library/Caches.

Next I upgraded to Sequoia 15.2, where apparently this cache over-filling is solved.

No problems now.

*in ~/Library/Containers/com.apple.mediaanalysisd one of the directories was humongous and filled 99.9% of free space. Go and check that directory in your ~/Library and by size it's immediately clear. Delete the oversize directory, and upgrade to MacOS 15.2 directly after that.

I could not upgrade to 15.2 prior to clearing this cache because, no free space...

I noticed this issue some weeks after upgrading to Sequoia, it probably appeared in Sequoia 15.1.

(the system had been creating a new mediaanalysisd cache file of 64MB probably every hour or so, without ever deleting the older ones. I saw an endless list of these 64MB files... On its own that sounds a small file, but in the end filled some hundreds of GB in that cache)

I have 15.2 installed. I had an unusually large amount of data in system that cannot be explained. The last time I checked it was closer to 33gb. I chunked the library folders and discovered that messages showed 46gb and iCloud Drive showed 52gb. in the storage section of the Mac iCloud Drive showed 23mb and messages showed 3gb. Those outliers are what the system data is using. Cache was closer to 2gb so deleting those files is pointless. moved the messages folder on a separate HDD and deleted that library file which resulted in all my messages removed. they can be restored from iCloud. the iCloud Drive file is not removable. you can turn off iCloud Drive and restart the computer but there was no change in the file size.

This is a bug and should be reported and a ticket submitted asap. Call don't message. get it done right

I have been having the same problem as well. Both Mac OS and system data were bloated. Mac OS registered at 41GB while system data registered at 281GB. My software was the earlier version of Sequoia.

I had a call with apple support earlier in the day we couldn't resolve it either and he mentioned that my Mac OS should not be at 41GB and should only be in the 20s territory.

I just upgraded my software to 15.3. Mac OS is now at 21.84GB and System storage is down to 183.98 GB (still high, but definitely decreased from the 281GB).

Hope this helps.

Hey, I'm struggling with this same issue right now. 320GB of my 500GB drive is system data. Did you figure something out in the last few months? I've tried what others have suggested; putting my drive into private on spotlight and erasing the index files but it didn't seem to make a difference.

Each time I clear out space, the system data just takes up more.

My phone started having trouble a week ago - opening apps caused my phone to restart, apps wouldn't open (including my Tesla app which I needed to get back into my car), camera, phone, face ID, etc. Super unstable after the 18.3.1 update. I erased my phone and restored from backup twice after cleaning all large files off and the system data grew. It kept using all my storage and I couldn't clean it up. After working on it for days, I decided to erase, but not to bring anything over (no backup or anything) and still my system data was full. I did a DFU (device firmware upgrade) and while it took all day, it fixed the problem. I had to look the instructions up online and I restored a backup from a few days ago. Storage is freed up finally! I did open a support ticket and Apple is aware of the issue and working to resolve. That's the only info I could get. Best of luck.

I have found that one can boot into recovery on the Mac, erase the drive and reinstall the OS which will reset the system data file much lower but will again increase over time. I have done this on 3 Macs and works every time.

Go to this link and follow steps to disable spotlight.

I just did and reclaimed 160 GB on my iMac with 512 SSD.

Get Raycast as an alternative to Spotlight. It is free and does much more.

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Not sure if this was resolved. Another suggestion :

I saw elsewhere that Disk Drill has a useful space analyzer in the free edition.

Load it up and look down left side menu for Clean Up option.

Then you can dig into where data is piling up.

One thing I noted while clean installing recently and copying large files across from old maching to new via Thunderbolt connection was huge files in a folder in the User/Library folder.

I don't recall exactly where it was located any more but looking online indicated it was files being created for the Handoff feature.

From what I read, using Command C and V to copy the files was causing the issue. Dragging would not. Not 100% sure why but I deleted the "cached" files and used darg and drop and it seemed to resolve the issue.

Maybe something to check out if you are a keyboard shortcut user and moving large files around rather than a drag and dropper.

My knowledge runs out there, but it could also only apply if between two separate entities - Mac to Mac or Mac to external hard drive for example.

Had the same problem; fixed by going to Disk Utility, Show > Snapshots, deleting snapshots. These are disk images saving states of the system at different times to allow reversions, like an involuntary form of Time Machine.

What you did was to reindex Spotlight. You can also follow this process:

Rebuild the Spotlight index on your Mac - Apple Support