How to clear Photoshop scratch disk on Mac

"Under-of-disk space" error on Mac computers: a complete guide to solving the Photoshop scratch disk problem

It may not be common to deal with scratch disk issues on Mac computers, but it is crucial for users of applications such as Photoshop to understand how to solve this problem. Large programs like Photoshop, Premiere Pro, and Final Cut Pro often encounter this error, which can be very confusing.

This article will guide you how to clean the scratch disk on your Mac, clear the scratch disk space, explain why the Photoshop scratch disk is full, and how to better manage memory to reduce or eliminate the frequency of such popups.

What is scratch disk?

You can think of a scratch disk as a piece of draft paper. You take notes on draft paper; it could be the creativity of the book you are writing, or some illustrations hand-drawn before testing in a design application.

The scratch disk works the same way. Large, intensive applications require some hard disk space as virtual memory when RAM is insufficient to complete the task. Just like draft paper, it temporarily stores content while performing heavy tasks such as editing videos or photos containing many edits and layers. Although these files are temporary, they need a place to store - scratch disk.

Possible Causes	Solution	step
scratch disk full	Clean disk space	Open CleanMyMac X > Space Lens > Scan > Select the folder you want to delete > Click Delete.
Temporary files in Photoshop	Delete Photoshop temporary files	Open Finder > Search for .tmp file > Delete files starting with pst.
Photoshop cache	Clean up scratch disk in Photoshop	Open Photoshop > Select Edit > Clean > All.
scratch disk location	Mobile scratch disk	Open Photoshop > Preferences > scratch disk > Select a new drive > OK > Restart Photoshop.
The hard drive is full	Release RAM	Open CleanMyMac X > Maintenance > Free RAM > Run.
Continuous issues	Reset Photoshop	Open Photoshop > Preferences > General > Reset Preferences when Exit > OK > Restart Photoshop.
Older Macs with HDD	Upgrade to a larger drive	Contact a professional to replace the HDD with an SSD.
Newer Macs that cannot be upgraded	Use external drive as scratch disk	Connect an external drive > Open Photoshop > Preferences > scratch disk > External drive > OK.

Scratch disk full?

Photoshop's temporary files may fill your hard drive. Get CleanMyMac X on Setapp now to free up space.

What is the cause of scratch disk error?

The main reason you see the "Photoshop scratch disk full" error is the temporary file. If you often force exit applications like Photoshop, temporary files won't disappear. The application thinks you may need to use them later, so they will be saved. These files may also not appear as occupied memory, which increases the confusion about why you see the error message.

Other reasons you see this error are that the drive space on the scratch disk is inadequate; this is most common when your Mac's storage is full. Similarly, the partition used by Photoshop or other applications may also be full, and the limited RAM available to the application can also cause this error.

What should I do when the scratch disk is full?

When you see "Photoshop scratch disk full", there is no good solution for Mac computers. It does not automatically clear disk space, nor does it create a unique partition to avoid this problem. You have to understand the way to clean the scratch disk yourself.

How to clean the scratch disk

There are some tips and tricks to effectively clean the scratch disk, but remember that the best way is always to actively manage your memory. Here we will show you how to clean the scratch disk partition and show you some applications that may prevent the error from reappearing.

1. Clean disk space

You're here to learn how to clean the scratch disk in Photoshop, but the root of the problem lies in the messy storage space of your Mac. How often do you save projects and then stop using them?

CleanMyMac X has an incredible feature called Space Lens that provides an overview of the Mac storage composition so you can quickly identify which folders are overflowing. It analyzes your entire system and shows which folders are too large and provides a quick way to delete unwanted files. The operation method is as follows:

1. Open CleanMyMac X on your Mac
2. Select "Space Lens" from the left side of the window
3. Select Scan at the bottom of the window
4. When the application completes analyzing your Mac, select the folder you want to delete
5. Select Delete at the bottom of the window

The app also has a feature called Large and Old Files, which is very similar to Space Lens, but checks individual files by size. You probably saved a movie a long time ago and then forgot about it. CleanMyMac X will remind you and let you quickly and easily remove it from your Mac forever.

2. Delete Photoshop temporary files

Learning how to clear Photoshop scratch disk errors is sometimes as simple as deleting temporary files. To find and delete Photoshop temporary files, search for any file with the extension ".tmp" in Finder. Photoshop's file name begins with "pst", so any file that matches these parameters can be deleted.

3. Cleaning scratch disk in Photoshop

While you're wondering how to clean the scratch disk, Photoshop doesn't make it easy, doesn't it?

When you want to clean up a Photoshop scratch disk, you are actually deleting its cache. To do this, follow these steps:

1. Open Photoshop on your Mac
2. Select Edit from the menu bar
3. Select Clean
4. Select "All"
5. When the pop-up window appears, select OK

Now that your Photoshop cache is cleared, it can write more temporary files to the scratch disk.

4. Mobile scratch disk

You can also change the location of the scratch disk in Photoshop! One common way is to use an external drive as a scratch disk – just remember to plug it into your Mac.

Here is how to change the scratch disk location on your Mac:

1. Open Photoshop on your Mac
2. Select "Photoshop" from the menu bar
3. Select Preferences
4. Select "scratch disk"
5. Select the drive to use
6. Select OK
7. Force close Photoshop and reopen it.

Now the location of scratch disk has been changed!

5. Defragment hard disk when scratch disk is full

Macs don't need defragmentation, and if you're using a modern Mac with an SSD, you can actually damage the Mac by defragmentation. Macs with SSD drives manage file storage in a different way than older HDD Macs, so defragmenting them can actually cause damage.

Your best option is to create backups of your file system frequently. Get Backup Pro for Mac can help you automate backups, sync files between your computer and installed devices, and encrypt backups for security. You can also create projects in Get Backup Pro to save files for applications like Photoshop!

Backing up files is a good choice because sometimes cleaning up your application's cache or files can inadvertently corrupt or delete files you actually want to keep. Having backups is your safety net.

6. Release RAM in the terminal

Sometimes your Photoshop will freeze and freeing up clearable space may not help. In this case, trying to clear some RAM, insufficient memory on your Mac usually causes problems with intensive programs like Photoshop. With CleanMyMac X, RAM cleaning is the easiest thing to do:

1. In the application, navigate to Maintenance
2. Choose to release RAM
3. Click Run. That's it!

You can also manually release RAM in the terminal:

1. Open the terminal through Spotlight
2. Enter the command sudo purge
3. Enter your password

7. Reset Photoshop

If you try to fix the "scratch disk full" error using the above method, but it doesn't help, you may need to reset Photoshop to its factory settings. Note that this also resets your color settings and other settings to the original defaults. So after resetting it will take some time to get back to work. Here's how to reset Photoshop:

1. Go to Photoshop > Preferences > General
2. Reset preferences when clicking Exit
3. Click OK to confirm your operation
4. Restart Photoshop to continue resetting.

Alternatively, you can exit Photoshop, hold Command Option Shift and turn Photoshop on, without releasing these keys. When you see a dialog box asking if you want to delete the settings file, click Yes and reopen Photoshop. This should solve the scratch disk problem.

This should earn you a lot of memory and keep your Photoshop working stably. Try restarting Photoshop to see the difference.

8. Upgrade to a drive with more space

In some cases, you can try adding more storage to your drive, but this is only possible if you have an older Mac. For example, 2012 and earlier versions of Macs are equipped with HDDs that can be replaced with SDDs (a modern and fast Mac storage drive). Newer Macs mostly use SSDs and are difficult to replace. Generally, all Macs in 2016 and beyond have built-in drives that are not upgradeable, so you have to look for an alternative solution – clean up the current drive or use an external drive as a scratch disk.

If you find that you can upgrade the built-in drive, please contact a professional Apple service to do the job – a very important task that requires solid expertise.

Is it possible to clear the scratch disk without Photoshop open?

Using CleanMyMac X is the best way to clear temporary files and clean the scratch disk space on your Mac without digging into Photoshop. Remember that scratch disk only saves temporary files, and these files are not always deleted by themselves when not in use.

CleanMyMac X's "maintenance" module has a feature called "free clearable space" that can handle temporary files stored on scratch disk space. While running the entire maintenance module and keeping your Mac in perfect condition may be a good idea, freeing clear space is very useful when you only need to free up space on the scratch disk. Remember, Photoshop should be turned off when running this module!

How to clean scratch disk on Windows

Unfortunately, if you are using a Windows computer, you will not be immune to the "scratch disk full" error. Here is how to clean the scratch disk on Windows:

1. In Photoshop, select Edit > Preferences
2. Click the scratch disk and select the drive used as scratch disk
3. If the free space is less than 40GB, delete large files from disk.

You can also consider deleting temporary files – on Windows computers, they are generated the same way as they are on your Mac. To do this, please exit Photoshop and go to C:\Users\Your Username\AppData\Local\Temp. You can delete all files that contain "temp" in your name.

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Photoshop's function is a gift and a curse. When it comes to editing photos, it can do almost anything you want, but it's resource-intensive. Cleaning up scratch disk space may not be your day job, but if you are a Photoshop power user, you will most likely encounter it at some point.

Photoshop's "scratch disk full" error can be annoying, but it's easy to fix. The key is to maintain the storage space of your Mac. Regular maintenance, such as cleaning up temporary files, caches, and system garbage, is crucial. For detailed steps on how to keep your Mac optimized, check out this article "How to Clean and Optimize Your Mac".

Both Get Backup Pro and CleanMyMac X are available through a seven-day free trial of Setapp, a powerful suite of productivity apps for both Mac and iPhones. After the trial period, Setapp offers unlimited access to the full app directory for only $9.99 per month.

FAQ: How to clean the scratch disk

Why does Photoshop show "scratch disk full" and the hard disk still has space?

Photoshop can use your hard drive, SSD, or even external drive as a scratch disk. So you may be checking for the wrong disk space. You can read more about assigning scratch disk here. It is recommended that you do not use the main drive (the drive that installs macOS) as the scratch disk for Photoshop.

Another reason might be that even if your drive has space, it lacks unfragmented space—which is crucial for Photoshop to work properly. Some materials recommend running disk defragmentation in this case, but this is not always safe, so we recommend using Get Backup Pro to regularly back up your drive.

What does it mean to have scratch disk full in Photoshop?

This error usually means that you have insufficient RAM or disk space in the drive where your Photoshop scratch disk is located. This is a very common problem because Photoshop tends to generate a large number of temporary files in the background that pile up and mess up your drive.

How to prevent the scratch disk from being full in Photoshop?

Clean disks regularly using CleanMyMac X. It will delete junk files, including a large number of temporary files generated by Photoshop. A monthly cleanup is enough to prevent scratch disk from having full errors.

How to clean up scratch disk without Photoshop?

Use CleanMyMac X to clear temporary files and free the scratch disk space:

1. Open CleanMyMac X.
2. Select Maintenance.
3. Click Release to clear the space.
4. Run the maintenance module (make sure Photoshop is closed).

You can also manually delete Photoshop temporary files:

1. Open Finder.
2. Search for .tmp files.
3. Delete files starting with pst.

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