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Scratch Disk is Full

Free up space for the Photoshop scratch disk...

If you are experiencing the Photoshop "Scratch Disk is Full" error message, you can resolve the problem by following the steps outlined below.

If you are unaware of what a scratch disk is, you might like to read my short article on Scratch Disks, and then come back here.

How Did The Problem Arise?

There are a few main ways this problem can arise. To determine which course of action to follow, ask yourself these questions:

Did the error only start appearing after Photoshop crashed?

Does the error occur when editing most documents, or only when editing a particularly large document?

How much space is free on the hard disk holding the Photoshop scratch files, and has that hard disk been defragmented recently?

Photoshop Crashed

The most common reason for the "Scratch Disk is Full" error message is illustrated by Question 1. Photoshop creates large temporary files on the scratch disk, and then deletes them when it is finished, but if the program does not shut down correctly then these files can be left on the disk.

These temporary files will be named "~PST####.tmp" where "####" represents four numbers. These files will probably be stored in a directory named "Temp" or something similar, and are safe to delete while Photoshop is not running.

If you are unsure whether there are temporary files left on your system, try running a file search by clicking on the Start Menu, and selecting 'Search - For Files or Folders...'. You can then search for files with names containing "~PST".

Deleting these temporary files should free up space on the scratch disk, and stop the error occurring.

You're Working with a Large Image

When working with particularly large images, Photoshop requires much more memory than usual to accommodate the image editing. If you are producing images for a professional publication for example, and have chosen a very high resolution, this could explain why you are getting the "Scratch Disk is Full" error message.

Adobe recommend you first ensure that the image does not have a needlessly high resolution. They state that the resolution (Which you can set by selecting 'Image - Resize - Image Size...') is measured in pixels per inch (ppi), and not dots per inch (dpi).

They emphasize that you should not use the maximum dpi of your printer for the ppi of your image. Even a high-end professional printer than can print at 1200 dpi or higher requires only 200 – 300 ppi.

If you are sure that your image needs the large size and resolutions values you have specified, then you can still follow the steps below to free up more space on your scratch disk.

You Still Need More Free Space on the Scratch Disk

If you have deleted the temporary files, and are sure that you are not working with an unnecessarily large image, you can still follow the steps below to free up scratch disk space.

Firstly, consider the possibility of adding another scratch disk drive or changing the one Photoshop uses. To alter the scratch disk location, go to 'Edit - Preferences - Plug-Ins & Scratch Disks'. Using the four drop down boxes in the dialog that appears, pick the disk drives you want Photoshop to use.

If you have specified both the drive which contains you operating system, and another drive, it is generally best to specify the other drive as the primary scratch disk.

Photoshop will use up as much free space as there is on the disk drive, so ideally you should make sure there are at least a few GBs of space free on the drive.

Never specify network drives or removable drives for scratch disks.

Sometimes the "Scratch Disk is Full" error will occur even when the drive in question appears to have enough free space. This is usually because the drive has not been defragmented recently.

Photoshop requires that scratch space must be contiguous and unfragmented (All the space is together in one group), and over time free disk space can lose this characteristic. To restore it, run the Windows Disk Defragmenter Utility.

If you are running Windows XP, you can click on the Start Menu, and select "Help and Support". Type in "disk defragmenter" to the search box to find out how to properly defragment your disk drive.

It *Still* Doesn't Work!

If you've done all of that, then the following should be true:

You have at least one drive specified as a scratch disk for Photoshop.

There are no temporary files on that drive left from past Photoshop crashes.

There is a fair amount of free space on that drive.

You have defragmented that drive.

You are not working on an image with an unnecessarily high resolution.

If all of that is true, and you are still experiencing this error, your scratch disk drive may in fact not be the problem.

Sometimes the amount of RAM Photoshop has been told to use can cause this problem too, if it is too low or too high. Read more about this issue in my article on Photoshop Memory.

To alter the maximum percentage of memory used by Photoshop choose 'Edit - Preferences - Memory & Image Cache' from the menu. The Maximum Memory Usage value should generally be between 50% and 60%. On very high specification machines a setting as high as 75% may be appropriate.


The "Scratch Disk is Full" error is a common problem for many users of Photoshop and Photoshop Elements, especially those with slightly older computers. With a little care in selecting the drives used by Photoshop for temporary files however, and some basic maintenance of those drives, the problem should persist no longer.

Kind Regards

Robert Redwood Robert Redwood - Bio
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