User level: Level 1 (4 points)Hi all, I updated to macOS 27 a month ago and my System Data is rapidly growing. It went from 50 GB in the first two weeks to 90 GB now. On a 256 GB / 16 GB M4 model, using almost half the drive for system data doesn't seem normal. Any idea what's causing this or how to fix it?
[Edited by Moderator]
Posted on Oct 14, 2026 10:31 AM
User level: Level 9 (72,871 points)Oct 14, 2026 11:18 AM in response to cylinder_2
You should aim to have 15-20% of your total internal storage as free space (~30-40 GB as an absolute minimum). If you do not have enough free space on your Mac’s internal storage, then here are some steps to take to safely free up space:
Free up storage space on Mac - Apple Support
Optimize storage space on your Mac - Apple Support
How to free up ‘System Data’ and other st… - Apple Community
"System Data" comprises your data, but they are typically hidden files that Spotlight cannot assign to a specific category like Documents or Applications. Examples include Outlook attachments, iOS updates, Cloud storage caches, etc. Starting with macOS 27 Golden Gate, System Data also includes what macOS used to call ‘purgeable’ storage – system caches, Time Machine snapshots and some other data, though the user had no control over the purging. Trying to manually clean out hidden files in System Data is likely to cause more problems than it solves, macOS hides those files for a good reason. Follow the steps in the linked articles above.
On macOS 27, separate ‘purgeable’ space is no longer reported, and instead those data are now considered as used space. They are also now included in System Data, accounting for the apparent increase you (and others) have noticed. You didn't lose space, macOS just categorizes things differently now than on Tahoe.
More detail on this change in this User Tip:
System Data and Free Space Changes in Gol… - Apple Community
The best advice is to just ignore the System Data category. ‘System Data’ is merely a catch-all category for files that Spotlight cannot assign to specific categories like Applications, Documents, Photos, etc. In fact, what is now shown as System Data used to be reported as ‘Other’, Apple changed the label in macOS 12 Monterey. System Data probably sounds better, but Other was closer to reality.
User level: Level 10 (123,805 points)Oct 14, 2026 12:01 PM in response to cylinder_2
System Data taking up a large amount of storage is a common question on Mac.
There is no single setting that simply “clears” System Data because this category can include a variety of files, including caches, logs, temporary files, and APFS snapshots.
If you want the most comprehensive solution, back up first, erase the Mac, and reinstall macOS.
For Apple silicon Macs, use Erase All Content and Settings.
This removes your data, settings, and applications while leaving the currently installed version of macOS in place.
Make a current Time Machine backup before erasing anything. Apple: Back up your Mac with Time Machine
Afterward, use Migration Assistant to transfer your user account rather than the entire old system, and reinstall only the applications you actually need.
If you do not want to erase the Mac, first determine what is actually consuming the space. DaisyDisk can provide a clearer view of storage usage, and Apple documents how to view APFS snapshots in Disk Utility.
The following Apple Community discussions document additional approaches. Results can vary depending on what is responsible for the storage usage:
Also consider moving large personal files—particularly Photos, videos, music, and other files you control—to an external SSD.
This is often a more appropriate way to free internal storage than attempting to delete files that macOS manages as System Data.
User level: Level 9 (60,836 points)Oct 14, 2026 12:15 PM in response to cylinder_2
cylinder_2 wrote:
I updated to macOS 27 a month ago and my System Data is rapidly growing.
Yes. That's normal and expected.
It went from 50 GB in the first two weeks to 90 GB now. On a 256 GB / 16 GB M4 model, using almost half the drive for system data doesn't seem normal. Any idea what's causing this or how to fix it?
The only part that's abnormal about that is how remarkably low your System Data value was. 50GB is really great! No joke - best in class.
Unfortunately, then you upgraded. And you only have a 256 GB hard drive. You're out of free storage.
Ideally, you want to keep a minimum of 100 GB of free storage. And I don't mean "available" storage. That value is essentially a fantasy. Free storage is the only thing that matters. You can see your free storage in Disk Utility. Show all device and then look at your "container disk3" device under "Apple SSD". It will actually say "Free". That's your free storage.
(PS: Depending on many confusing and conflicting problems, your "available" might sometimes be the same as "free". Don't be fooled! It is not. Don't look at it. Just when you think it's reliable, something internal will change, or maybe Apple issues an update, and then it'll be fantasy again.)
I realize that you probably can't ever get to 100 GB free on a tiny 256 GB computer. Just do the best you can. You'll start to lose performance under 50 GB free. At 20 GB free, you may not be able to apply OS updates. Don't ever look at System Settings > Storage. The less free storage you have, the more wildly inaccurate that "Storage" display will be.
Originally posted at discussions.apple.com/thread/256376212