How to Fix “Scratch Disks Are Full” on Mac (And Why It Happens)
If you use Adobe Photoshop on a Mac, sooner or later you may see the frustrating message:
“Scratch disks are full.”
It often appears suddenly—sometimes when opening Photoshop, sometimes when saving a large file. The error can stop you working completely. The good news is that it is usually easy to diagnose and fix once you understand what is happening under the hood.
What a Scratch Disk Actually Is
A scratch disk is temporary storage Photoshop uses when it runs out of RAM.
When you edit images—especially large files with many layers—Photoshop needs space to store intermediate calculations, history states, and image data. When your computer’s memory isn’t enough, Photoshop writes that data to a scratch disk, which is typically your main system drive.
Think of it as overflow workspace for Photoshop.
If the drive is nearly full, Photoshop cannot create those temporary files and it throws the scratch disk error.
Why It Happens
On most Macs, the scratch disk defaults to the main system volume:
/System/Volumes/Data
If this volume runs out of space, Photoshop cannot allocate temporary storage.
In many cases the system might look like this:
Total disk: 460 GB
Used: 430 GB
Free: ~5 GB
That is far below what Photoshop requires.
For reliable performance, Photoshop typically needs 20–100 GB of free space.
Common Causes of a Full Scratch Disk
Several types of files commonly fill Mac storage without users realizing it.
1. Photoshop Temporary Files
Photoshop creates temporary files during editing sessions. Occasionally these remain on disk if the application crashes or closes unexpectedly.
These files often appear as:
PhotoshopTemp####and can grow very large.
2. Auto-Recovery Files
Photoshop saves recovery snapshots in case your computer crashes. Over time these can accumulate.
They are usually stored inside:
~/Library/Application Support/Adobe/Adobe Photoshop/3. System Caches
macOS stores application caches to improve performance. These caches can slowly grow to many gigabytes.
4. Hidden Large Files
Other hidden storage consumers may include:
iPhone backups
Video files
Download folders
Docker images
Development tools
Old project archives
Because many of these sit inside system folders, users often do not realize they exist.
How to Fix It Using Terminal
The fastest way to clear space is through the Mac Terminal.
Remove Photoshop Temporary Files
rm -rf /private/var/tmp/PhotoshopTemp*Clear Photoshop Auto-Recovery Files
rm -rf ~/Library/Application\ Support/Adobe/Adobe\ Photoshop*/AutoRecover/*Clear User Cache Files
sudo rm -rf ~/Library/Caches/*Empty the Trash
rm -rf ~/.Trash/*Check Remaining Disk Space
You can confirm how much storage is available using:
df -hIdeally you should aim for at least 40–60 GB free.
Finding What Is Taking Up Space
Sometimes the scratch disk error is only a symptom of a deeper storage issue. To identify large folders quickly you can run:
du -h -d 1 ~ | sort -hr | head -20This command shows the largest folders in your home directory so you can quickly identify storage hogs.
Long-Term Solutions
Once you have freed space, there are several ways to avoid the problem in the future.
Use a Dedicated Scratch Disk
Photoshop allows you to assign a different drive for scratch files.
You can change this in:
Preferences → Scratch Disks
An external SSD works particularly well for this purpose.
Maintain Free Space
Keeping 10–20% of your disk free prevents many performance problems on macOS.
Reduce Photoshop History States
Photoshop stores every step you take as part of its history. Reducing this setting lowers disk usage during editing.
Regularly Clear Cache Files
Caches build up gradually. Clearing them every few months helps maintain disk health.
Why This Error Is So Common
Modern creative workflows involve extremely large files—often hundreds of megabytes or several gigabytes. When multiple layers, filters, and smart objects are involved, Photoshop may temporarily require many times the file size in scratch space.
A 2 GB image can easily require 20–40 GB of temporary disk usage while editing.
That is why even computers with large drives can occasionally hit the scratch disk limit.
The Key Takeaway
The “Scratch disks are full” error is rarely a Photoshop bug. Instead, it is a signal that your system storage is running out.
By clearing temporary files, removing caches, and maintaining adequate free space, you can prevent the issue entirely and keep Photoshop running smoothly.
Once you understand how scratch disks work, fixing the problem usually takes less than five minutes.