I've deleted many files from photos, messages, etc., but the System Storage is at 425GB. I've emptied the Trash. When I go to General—Storage—there is no "Recommendation" window for optimizing System Storage. I'm at a loss at why that folder is so huge!
MacBook Pro 16″, macOS 15.3
This comes up a lot.
Short version: Deleting a file (or files) does not immediately reclaim the space they used.
This is especially true if you're using Time Machine. Time Machine keeps 'snapshots' of your system for easy recovery. The most recent snapshots are kept on the same disk for speed (on the basis you're more likely to want to recover a file you deleted an hour ago than you are 6 months ago), but are moved to external storage over time (if you have an external disk configured for Time Machine backups).
As such, while you delete the 'live' copy of a file, it still exists in the snapshots for some period of time.
Guess where the snapshots are reported? Right! under 'System Data'.
The long and the short of it is that the files are still on disk (think of them as 'hidden') and will eventually age out and get deleted (this can take hours to days, depending on your setup).
If the OS needs the space, then it will delete the old snapshots and caches to make room, so it's not really affecting the operation of the system, but it is a little opaque.
If it really bothers you and you want to see more space/less 'System Data', open Disk Utility.app and go View -> Show APFS Snapshots.
You'll see a list of the snapshots that are still on your local drive, and can delete them from here if you're really sure you don't need them:
This comes up a lot.
Short version: Deleting a file (or files) does not immediately reclaim the space they used.
This is especially true if you're using Time Machine. Time Machine keeps 'snapshots' of your system for easy recovery. The most recent snapshots are kept on the same disk for speed (on the basis you're more likely to want to recover a file you deleted an hour ago than you are 6 months ago), but are moved to external storage over time (if you have an external disk configured for Time Machine backups).
As such, while you delete the 'live' copy of a file, it still exists in the snapshots for some period of time.
Guess where the snapshots are reported? Right! under 'System Data'.
The long and the short of it is that the files are still on disk (think of them as 'hidden') and will eventually age out and get deleted (this can take hours to days, depending on your setup).
If the OS needs the space, then it will delete the old snapshots and caches to make room, so it's not really affecting the operation of the system, but it is a little opaque.
If it really bothers you and you want to see more space/less 'System Data', open Disk Utility.app and go View -> Show APFS Snapshots.
You'll see a list of the snapshots that are still on your local drive, and can delete them from here if you're really sure you don't need them:
Unfortunately, it's not very easy to do so.
System Storage encompasses a wide variety of files and data from vastly different places in the macOS system.
The first thing you'll want to do, is restart your Mac. If you haven't done so in a while it can accumulate a ton of caches and files it no longer needs but has not deleted. Usually a restart clears this up and reduces the system data significantly.
Then you'll need to systematically go through folders in places such as Library and Documents and see what's using up the most storage.
See the following post:
System Data sort of explained - Apple Discussions
DaisyDisk was recommended to find the largest files. DaisyDisk
How can I manage my MacBook Pro's System Storage—it's at 425 GB?
