I have a 2023 Macbook Air with M2 chip, 512 gb hard drive, 16 gb RAM, running Sequoia 15.7.3. My system settings show 162gb of storage consumed by "System Data". What is this and how do I reduce it?
MacBook Air 15″, macOS 15.7
My system data is about 109 GB. On thing I do to reduce it is launch Disk Utility and remove all but the latest local snapshot:
There's not a lot you can do to reduce it except the above and to move some folders to an external drive. Here's how I worked around the problem other than the above:
I wanted to keep a minimum of 100GB of free space at all times for optimal system and application performance. :
1 - get an external SSD drive and format it APFS. (I recommend OWC (MacSales.com))..
2 - copy the Pictures, Movies, and Music folders to the external SSD.
3 - make sure the libraries in those folders work as expected on the external SSD.
4 - once confirmed the libraries are working OK on the SSD delete the contents of the Pictures, Movies an Music folders. DO NOT delete the folders themselves.
5 - rename the folders on the SSD to Pictures-2, Music-2 and Movies-2.
6 - remove the original folders from the Finder's sidebar and replace them with the -2 folders by dragging them from the SSD into the sidebar of an open Finder window.
You have to reveal the hidden APFS snapshots in Disk Utility (Apple loves to hide things from people). See the following Apple article for details:
View APFS snapshots in Disk Utility on Mac - Apple Support
FYI, Time Machine APFS snapshots will automatically be deleted at some unknown time in the future. Usually they are deleted about 24-48 hours after the backup has been transferred to external media. Third party backup software which leverages the APFS snapshots may have different rules & behavior.
Edit: When you delete stuff to make more Free space, it won't be reflected in Disk Utility until the TM backups have been transferred to external media and those snapshots deleted.
Also, the only accurate storage value is the Free storage space value shown only in Disk Utility or the System Profiler. Ignore the very misleading "Available" storage value shown everywhere in macOS since "Available" is not synonymous with Free in macOS.
Sometimes you may see a "Purgeable" storage value alongside the "Available" storage value (usually in "Get Info"). If so, then you can calculate the Free space value from them:
Free storage = Available - Purgeable
Thanks for all of your ideas. It appears that half, or more, of the system data, are Time Machine snapshots that I could delete. However, I expect they will come back quickly. I appreciate all of your quick responses; I may just live with what I've got since I still have plenty of storage available.
This is all my Disk Utility shows:
I run Time Machine on an external drive. I store all photos and most of my files in iCloud.
If all else fails then erase your drive and reinstall the OS and files from your backup. This is the only way I found to really impact the system data number if the other good suggestions fail.
System data take up too much disk space.
