Mac Mini storage full and System Data size not calculating

CPW wrote:

My MacMini is maxed out on storage and is having issues. macOS Version 15.6.1 Build 24G90.

Applications are taking up 383.4GB, and it is unable to calculate the size for System Data, wheel just spins.

I have a lot of Photos so moved those to an external drive.

Clearly I have to clean some things out, but not sure where to start.

Start with any of the files and folders in your Home folder. In practice they are the only things you can safely move and delete from the Mac. Copy what you can to an external drive and then delete those items from your startup drive. Don't neglect to empty the trash and restart the Mac to clear caches and free up space as you go.

What you can do to create more free space:

• Empty the Trash in the Dock. 

• Empty the trash in the Photos app.

• Delete unused and unneeded application installers from your downloads folder and desktop. No need to store on your Mac what you can freely download any time.

• Reboot your Mac at least weekly. Let the OS do its housekeeping.

• Transfer files that you don’t use daily to an external drive and then delete them from the startup drive and empty the trash. Files that take up the most room are movies, images and music.

This from Apple on the subject of freeing up space:

Free up storage space on Mac - Apple Support

Also, please see the following guidance from Apple: 

Find and delete files on your Mac - Apple Support

MacOS may keep a number of Time Machine snapshots on the drive as part of the backup process.  These snapshots can occupy a significant amount of drive space. You can view and manage these in Disk Utility or in the Terminal app.

View APFS Snapshots is Disk Utility on Mac - Apple Support 

You can also use apps such as DaisyDisk from Software Ambience or OmniDiskSweeper from Omni Labs to find large files on your drive.  Once you've located these larger user files, you can relocate them to another drive and/or delete them if they aren't needed.

The storage space eye-candy is convoluted, inaccurate and may never finish calculating System Data.

For starters, check to see if you have APFS snapshots that are using storage space.

View APFS snapshots in Disk Utility on Mac - Apple Support

Next startup in Safe Mode followed by a normal restart.

Start up your Mac in safe mode - Apple Support

Then confirm your disk usage and free space by using Get Info on the Macintosh HD and Disk Utility.

And/or use a good third-party App like OmniDiskSweeper to evaluate User usage.

https://www.omnigroup.com/more/

If you just moved your Photos Library to an external storage drive.

Move your Photos library to save space on your Mac - Apple Support

1) Test that Library before you delete the original on your Mac's storage drive.

2) Make sure that the Library is backed up by TM and/or a second external drive for safety.

3) Wait several days for the APFS storage space to adjust and reflect the correct amount of free space.

FWIW you can also move your Music and Movie Libraries if necessary.

Change where your music files are stored on Mac - Apple Support

Move your iMovie for Mac library - Apple Support

CPW wrote:

HD storage is listed as 478GB of 494GB used. I deleted a couple apps I don't really need after backing up their data.

In a perfect world you'll need to always always maintain a minimum of 10%-15% of your startup drive's total capacity as free space so that the OS can do what it need to run your computer properly. If you allow the free space to drop too low it will affect performance and may even prevent the Mac from booting. Your target should be no less than 50-75 GB free space always, or a max of 425 GB used storage space ever.

Applications now occupy 391GB which is by far the biggest user, no surprise there. Messages is 2.41 GB which seems like a lot but could be mostly photos. Next is Documents at 156.7MB. Acrobat is taking the largest bite at 1.75GB followed by Evernote at 889MG.

Seems like I need to free up even more space from the HD but not sure how to do that.

Yes, you do need to remove even more stuff.

Note those file sizes. 1 GB (gigabyte) is = 1000 MB (megabytes). So don't bother dinking with files in the MB size range as that's pretty much a waste of energy and time.

You want to remove perhaps another 50-60 GB of data from your drive.

After you move files and folders to an external drive, you must delete those things from the startup drive, and very importantly, empty the trash. Also a good idea to restart the Mac at some point in the process.

I have lots of external drives I could use. I moved my pictures (10.71GB) to an external drive.

Looking for ideas on reducing memory usage.

Move your photo library or even the entire folder. Pics and vids can take up lots of space.

If you tend to download lots of stuff - application installers, .PDFs, etc. - from the internet, consider deleting most if not all of the stuff in your downloads folder. If you found it for download once, you can find it again. No need to store on your Mac what can easily be downloaded again.

"Mac Mini storage full and System Data size not calculating: My MacMini is maxed out on storage and is having issues. macOS Version 15.6.1 Build 24G90. Applications are taking up 383.4GB, and it is unable to calculate the size for System Data, wheel just spins. I have a lot of Photos so moved those to an external drive. Clearly I have to clean some things out, but not sure where to start."

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Try my User Tip: How to Use Finder to Clear “System Data" on a Mac - User Tip