If you’ve used Photoshop for any amount of time, you’ve probably encountered the dreaded “scratch disk is full“ error at least once. This error can even stop you from opening the app and occurs in all versions of Photoshop on both Windows and Mac. It’s frequently encountered when increasing image resolution in Photoshop or trying to load too many images at once. Here’s how you can clear the scratch disk in Photoshop to free up space.
- 1 What is a scratch disk?
- 2 How to clear your Photoshop scratch disk
- 3 Can I use an external hard drive as the scratch disk in Photoshop?
- 4 Other solutions for the “scratch disk full” error
What is a scratch disk?
A scratch disk is a storage area on your Mac or Windows computer that’s used as temporary storage for Photoshop– temporary settings, cropped pixels, etc, when there is not enough space in your RAM. Often the size of the Photoshop needs for the scratch disk can fluctuate wildly based on what you are editing. Photoshop thus needs ample disk space to run smoothly.
Even if you don’t see a scratch disk full error, you may need to empty the scratch disk or increase its size if Photoshop becomes too slow. You may for example notice that zooming in and zooming out feel choppy.
How to clear your Photoshop scratch disk
Fixing the “scratch disk full” error is mostly a matter of freeing up disk space. Below is our recommended way to do this on Windows and Mac computers:
Step 1: Purge the Photoshop cache
If you can still access Photoshop, open an image in the program and navigate to the “Edit” menu on the top of the screen. Go to “Purge” and click “All” to remove cached files from the scratch disk. If these items appear greyed out, this means that there are no cached items to delete.
On Mac, you can do the same thing by navigating to Photoshop CC -> Purge -> All
Step 2: Delete temporary files
Photoshop will sometimes leave a rather large assortment of temporary files sitting around on your hard disk. Removing them will free up space for both your scratch disk and other programs on your computer.
This is also the first step you should take if you want to clear the scratch disk without opening Photoshop.
Deleting Photoshop temp files on Mac:
- Go to Terminal
- Type “open / tmp”
- Delete all files starting with “Photoshop Temp”
Deleting Photoshop temp files on Windows:
- Open File Explorer
- Navigate to C:\Users\Your Username\AppData\Local\Temp
- Delete all files starting with “Photoshop Temp”
You can also search your computer for “Photoshop Temp”. You can also search for files that begin with “pst” or end in “.tmp”, Be sure to include hidden files and folders in your search.
Step 3: Allocate more memory to Photoshop
Photoshop will first try to use your memory (RAM) before allocating data to the scratch disk. Allowing the program to use more memory can improve performance and prevent it from having to ever go near the scratch disk in the first place.
To do this on Windows, go to Edit -> Preferences -> Performance. On Mac, simply go to Photoshop CC -> Preferences -> Performance. Navigate to Memory Usage. Move the slider to increase RAM access.
RAM is much faster to access than your hard disk. Consider upgrading your computer with more memory to boost performance in Photoshop if scratch disk access becomes a frequent issue.
Step 4: Add a scratch disk or change your scratch disk
You can also add a new scratch disk if you have an external hard drive or another partition. To do this on Windows, go to Edit -> Preferences -> Performance. On Mac, go to Photoshop CC -> Preferences -> Performance. Navigate to Scratch Disks. From this menu you can choose a new scratch disk.
From here you will have to restart Photoshop for the change to take effect.
On Mac, you can also press “Command+Click” when launching Photoshop to manually choose a new scratch disk.
Can I use an external hard drive as the scratch disk in Photoshop?
Absolutely! You can use the steps above to select any external hard drive as the scratch disk in Photoshop. Keep in mind that depending on the specifications of the hard drive, you may suffer degraded performance. USB‑C and Thunderbolt drives, especially SSDs, should work very well.
Older USB and Firewire drives will perform slowly and are probably not worth using as a scratch disk.
Other solutions for the “scratch disk full” error
The standard advice for freeing up space on your computer also applies here. Empty your Trash / Recycle Bin to remove unused files. Delete any unneeded programs. On Windows, you can also defragment your hard drive. Close any other open files, including other Photoshop images, and programs to free up space.
It may also be that the file you are working with is simply too large. You’re less likely to encounter the “scratch disk full” error when working with smaller files. Consider if you really need to be working with such a large image and if not, make the canvas area smaller to free up resources.
If all else fails and you keep encountering scratch disk issues on your computer, your work may have outgrown your computer. It may very well be time to upgrade your PC or MAC for better performance, especially if it is already 4+ years old and you are working with especially large files. Or you might want to consider a Photoshop alternative that has lower system requirements.