How to Clear Scratch Disk

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How to Clear Scratch Disk

If you have received a message that your scratch disks are full, here's what you need to know to fix it.

When Photoshop is running, it uses a scratch disk as a local storage drive. This virtual hard drive takes advantage of the storage on your computer (HDD or SSD) to keep files that cannot fit in or are not required to be in RAM.

Photoshop's scratch disk is set to be your boot drive by default. Your boot drive may acquire temporary files from a variety of programs on your PC over time, as most of them will utilise it in some way.

This can result in errors saying that your Photoshop scratch disks are full.

8 Ways To Clear Your Scratch Disk

Clear Photoshop Cache

If you wish to empty Photoshop's scratch disk, you should start by clearing the cache. Even though Photoshop deletes the cache automatically when you exit the software, some items may be missed.

Here's how to clear the cache in Photoshop completely:

  1. Open Photoshop.
  2. Select the Edit menu.
  3. Click on Purge.
  4. Choose 'Select All' to clear all caches, or select individual caches to clear (Clipboard, Video Cache, or Histories).

You can also erase system caches on Mac to make it cleaner and faster. While you're at it, you may want to use a cleaning app for Mac or a PC cleaner to quickly remove your browser cache, cookies, and other miscellaneous junk files.

Delete Photoshop Temp Files

Photoshop saves temporary files as a backup in case your computer or software crashes, but it doesn't erase them once you've finished working on a project. As a result, these useless files might linger and take up a lot of space.

Here's how to clean up Photoshop's temporary files:

  1. Close all open projects to avoid potential data loss.
  2. Exit all Adobe apps.
  3. Use Finder to search for /tmp and open the folder.
  4. Delete any folder that contain the word 'Photoshop'.
  5. Empty your Trash to recover the disk space used for scratch files.

Another option to free up space on a Mac is to look through your Other storage, which contains files that aren't as frequent. Some of the data in this folder should not be removed, so read our guide on how to clear up other space on Mac first.

Clean Up Your Computer's Storage Drives

Cleaning up your computer's hard disks should always be the initial step. Users of Mac and Windows can utilize their native disk cleanup applications, such as Windows' space-clearing Disk Cleanup utility. You can also utilize trusted third-party programs like CCleaner Free or Pro.

This step is listed first because it may correct problems with your computer's operating system and any background processes.

Disk cleaner software will delete browser data like your browsing history, cookies, temporary internet files, recently visited URLs, and index files. It will also automatically clear system junk like temporary files, memory dumps, log files, chkdsk file fragments, and error reporting logs.

After each session on your computer, take a few moments to run your disk cleanup tool. This will help eliminate Photoshop "scratch disks full" issues, as well as enhance the speed and performance of your machine in general.

Additionally, minimize the number of applications running on your computer when using Photoshop.

Free Up Additional Storage Space

When you receive the 'Scratch disk full' error, it usually implies that your scratch disk drive (or drives) have run out of space or are running short on space.

It's possible that you'll need to free up more hard drive space. You'll need to do the following to accomplish this:

You can accomplish this by deleting temporary files from the scratch disk or moving unneeded files to another storage drive.

If you're unsure which drive holds the Photoshop scratch disk, follow these steps to find out:

Photoshop scratch disk settings

Go to Edit > Preferences > Scratch disks in the Photoshop software.

The scratch disks are usually found on the C: drive. Once you've found it, double-check that the storage device has more than 45 GB of empty space. If you don't have enough disk space, you will need to delete unnecessary files until you have enough room for Photoshop to function.

Move Photoshop Scratch Disks to Another Drive

Setting the scratch disk to another drive is the easiest and fastest way to free up storage space if you need additional scratch disk space. Scratch disks are saved on your system drive by default, but you can alter this by opening Photoshop and selecting Edit > Preferences > Scratch Disks and then setting it to use a new drive or several drives. Scratch disk space can be assigned on up to four drives or SSD drives.

If your primary boot disk is a SSD, you can utilize it as the scratch disk without incurring any performance cost, as long as it has sufficient free space to operate properly. However, if your primary drive is a hard drive, setting the scratch disks to a different location will result in a performance boost. As long as you're utilizing a Thunderbolt or USB 3.0 connection, even an external storage device can be used without hurting performance.

Go to Edit > Preferences > Scratch Disk to choose the drive Photoshop uses for scratch disks. Then pick or deselect the storage devices you to use using the checkboxes. Scratch space can be assigned to up to four drives. External drives with a high-speed connection are good, but if the disk wasn't attached when Photoshop launched, you'll have to restart it before it recognizes it as an option. Before the modifications to the scratch disks take effect, you'll need to restart Photoshop.

Change Photoshop Settings To Use More RAM

You can boost your temporary storage by allowing Photoshop to use more RAM. To raise the amount of memory (RAM) Photoshop is allowed to use follow these steps:

Photoshop memory usage settings
  • Select Edit > Preferences > Performance > Memory Usage.
  • Under 'Let Photoshop Use', raise the amount of ram Photoshop will be allowed to use.

Photoshop defaults to a maximum of 70% RAM usage but this may not be ideal for your configuration. If your computer has plenty of memory, raising this allocation will allow Photoshop to avoid using the scratch disks nearly as much.

Disable the Auto Recovery Feature in Photoshop

When using Photoshop, your project is automatically saved as you go. You will save storage space on the scratch drive if you disable the Auto Recovery option. However, this should only be used as a last resort as it will disable automatic saving of your work, resulting in potential data loss if Photoshop crashes.

To disable automatic recovery, select Edit > Preferences > File Handling and de-select the box marked 'Automatically Save Recovery Information Every'.

How To Fix Photoshop Not Opening Due to "Scratch Disks Full" Error

In extreme cases, Photoshop may refuse to launch at all, instead displaying a popup box informing you of a "scratch disks full" error.

When this happens, press Ctrl + Option on Mac or Ctrl + Alt on Windows to open Photoshop. This will enable you to gain access to Photoshop via an override and resolve the issue.

What causes errors that a scratch disk is full?

Temporary files are the most common cause of 'Photoshop scratch disk full' issues. Temporary files do not get deleted when you an app is force-quit or if Photoshop crashes. The program keeps them because it thinks you'll want to utilize them later. These files may not appear as occupied memory, which adds to the puzzle of why you're seeing the error notice.

Other explanations for the problem include a lack of space on the storage device where the scratch disk is housed, which is most common when your hard drive becomes full. Similarly, the partition that Photoshop uses may be overly large, and the app may only have a restricted amount of RAM.

How Much Scratch Disk Space Do You Need?

Photographers already have a hard drive space problem (all those enormous RAW files add up), but it's critical to reserve adequate space on your device for Photoshop's scratch files. Photoshop automatically reserves 6 GB of storage space if your scratch disk is set to your main hard drive. It sets aside 1 GB of space on non-system disks. However, the amount you actually require differs from what Photoshop reserves, and it fluctuates significantly depending on what you're doing in Photoshop.

Adobe estimates that you'll require 1.5 GB plus double the size of all files you may have open at the same time for smaller operations and revisions. They suggest multiplying current document sizes by the number of history states for large processes and complex updates (you can change the number of history states by heading to Edit > Preferences > Performance).

In practice, file sizes quickly accumulate, particularly when working with huge files that contain numerous layers or image files. As a result, ensure you have enough of free space on your hard disks.

Author Katrina O'Reilly
About The Author
Katrina O'Reilly
Katrina goes by her gamer handle MissTRex. Born in Jaynesfield Wisconsin, she studied game design at Full Sail University. She has a penchant for anything "geeky" and is still a huge gamer.