I installed the macOS 27 update on my 2024 Mac mini overnight, and afterward I noticed that I had significantly less free space than before.
My Mac mini has a 500 GB SSD and 24 GB of RAM. According to the Storage settings, macOS itself is using about 28.8 GB, while System Data has grown to around 121.6 GB. My applications are using another 89.9 GB, with roughly half of that coming from photo and video editing apps.
The size of System Data seems much higher than it was before the update, and I’m now missing roughly 125 GB of usable storage.
Could the update have created temporary files, caches, snapshots, or other data that are being counted as System Data? Is there a safe way to identify what’s taking up the space and recover some of it?
I noticed something similar after updating my Mac. System Data jumped quite a bit, and at first I thought the update had permanently eaten the space.
In my case, I didn’t immediately start deleting things because macOS can temporarily use extra space for things like update files, caches, and local snapshots. Some of that space may also be released automatically later.
I’d give it a little time and restart the Mac first. Then check Storage again. If System Data is still around 120 GB after a day or two, I’d start looking for what’s actually using the space rather than deleting random files from the Library.
I have used a Mac cleaner called iBoysoft Cleaner to help me clean up my Mac as part of my routine. This software helps smartly scan the system junk files, including system cache, log files, app caches, old downloads, and more, and lets you delete them with one click.
I believe that our Mac has accumulated junk files during our work. So, it’s not the update result in space loss but the daily space uasage.
I’d check local Time Machine snapshots before assuming the 125 GB is really being permanently used by macOS.
Open Terminal and run:
tmutil listlocalsnapshots /
If you see a lot of snapshots, that could explain part of the large System Data number. macOS normally manages these automatically, so I wouldn’t manually delete system files just to bring that number down.
Also keep in mind that the Storage panel isn’t always a perfect representation of what’s physically occupying the SSD. I’d first find out what’s behind that 121 GB figure.
If it stays that high and you really need the space back, you can then look at caches, old update files, Time Machine snapshots, and large application support files one by one. I’d definitely avoid using a “cleaner” to blindly delete System Data.