Scratch disk not reflecting actual space available

You are experiencing the difference between actual free space and purgeable free space.

When you look at what's Available in Disk Utility (or simply getting Information (Cmd-I) on the drive on the desktop), what you are seeing is the "potential" free space, which is the sum of the "actual" free space + "purgeable" (what Apple's OS could glean if it purges unnecessary "stuff"). Time Machine snapshots can be part of that, as mentioned, but it's not the whole story.

Unfortunately for you, Photoshop can only make scratch disks out of REAL free space.

In your case...

...your reported "Available" is the total of actual free space and the purgeable, so 117 less 112 equals about 9 GB.

There are some utilities out there that can help clean out some of this purgeable data, and you can help a bit by selecting Manage.

The bad news here is that your drive is actually starting to get full, so unless you have an external to act as a second Scratch Disk, you're situation is not going to get better unless you start removing things.

You may be running into a quirk with how macOS reports free space for APFS volumes, especially if local Time Machine snapshots exist. Read the following articles and see if deleting some old local snapshots both frees up more space, and maybe brings the two different free space amounts closer together.

Explainer: Disk free space – this explains why a Mac might report multiple, different amounts of free space simultaneously.

Managing snapshots: how to stop them eating free space

Hi!

I'm using Photoshop 2022 23.2.1 and macOS Big Sur 11.1

I didn't have any documents open when checking the scratch disk space.

I updated the permissions and restarted as per your instructions and nothing changed.

Hi there,

Thanks for reaching out. Sorry for the trouble with Photoshop. We are here to help.

 Could you please confirm the version of Photoshop you are working on along with the exact version of the operating system you are working on? Are you seeing 13GB available in Photoshop when you have any documents open in Photoshop, or there are no documents open when you are checking the scratch disk?

From launching Photoshop to opening documents, the scratch space Photoshop reserves can temporarily grow. If you have any documents open please close them and then check Scratch Disk in Preferences.

Please ensure Photoshop has required permissions to access the storage of your macOS machine by following these steps:

1.  Go to the System Preferences for your Mac, then Security and Privacy, then select the Privacy tab.  
2. Then select Accessibility from the list to the left & check if Photoshop is added to the list with a checkmark in front of it.  
3. If Photoshop is not a part of the list, please add it by unlocking the window first using the lock at the bottom left, then clicking the + Icon & navigating to the Applications folder.  
4. Also, grant permissions to Photoshop under Full disk access found in the same list as Accessibility.

5. Once done, restart the Mac & check if it helps.

Please let us know if this helps.

Regards,

Sameer K