Scratch disks are full on a Mac? Here’s a solution

6 min read

If you've encountered the Photoshop scratch disk full error on your Mac, you might be wondering what a scratch disk is? And how can I resolve the error message? Keep reading; you're in the right place. 

You may begin to see this message if you frequently work with the creative Adobe Suite. Let's not waste any time; we’ll explain how to eliminate “the scratch disks are full” error and keep your machine in tip-top shape to stop it from happening again.

What is a scratch disk?

When you use intensive programs like Photoshop, they need working space known as virtual memory and sometimes cache memory. A scratch disk is an available space on an SSD or disk drive.

Photoshop, for instance, uses this space to store parts of your working documents, layers, and editing history when there isn't enough RAM. Even though these files are temporary, they still need a place to live, enter the scratch drive. 

Did you know? When working on a large or complex project in Photoshop, it's quietly producing a huge amount of temporary project files that eat away at your drive space.

What is a scratch disk full error on Mac? 

When you see a scratch disk error message, you can bet the most common reason is an excessive build-up of temporary files. 

Temporary files can accumulate without leaving a trace of their existence, making it tricky to diagnose; they often aren't visible as occupied memory. 

If you force quit Photoshop regularly, you might have tons of temporary system files lurking around, which Photoshop has saved for you, just in case. 

Other common reasons to see the scratch disk full error on Mac

  • You’re running out of free space

  • Limited RAM is available for Photoshop to use 

  • Photoshop's disk partition is full

Whatever the reason, you'll be wanting to solve it quickly and get back to work on your epic project. Here are some great tips to resolve and clear your scratch disk.

How to clear scratch disk without opening Photoshop

1. Clear photoshop cache

Cache and other system junk have a lot to answer for. Left unattended, the build-up can start to cause numerous issues for your Mac, just like Photoshop scratch disk full error. 

If you can't open Photoshop due to the scratch disk error, you'll need another way to clear your cache, and that's why this is my #1 tip. 

If you run regular maintenance on your Mac, you can avoid issues like this altogether. Using a smart tool like CleanMyMac X can help ensure your Mac always has enough free space and RAM to run all apps smoothly.

CleanMyMac X’s System Junk module can clear all of your outdated caches that slow down your Mac and optimize your system in minutes. Here's how:

  1. Open the app — download the free version here.

  2. Now, select System Junk from the left sidebar and press Scan.

  3. Wait for the scan to complete and press Clean. 

2. Remove temporary files

Photoshops temporary files eat away your scratch disk space; it's a good idea to run a search for them and remove them, buying you back some valuable space, here's how:

  1. Open a new Finder window.

  2. Search for any files with the extension ".tmp.” Photoshop always begins its filename with "pst,” anything matching those parameters can be deleted. 

How to find .tmp files

3. Clear your disk space

The root cause of scratch disk errors is storage space. So, it's time to spring into action. First steps, check your storage; here’s how:

How to check storage on Mac

  1. Select the Apple Menu.

  2. Select About This Mac > Storage.

Take a good look at your overview; you can hover over the bars to see what each color represents. 

What can you remove to free up storage on your Mac? If you have an external drive or cloud storage account, now is a good time to think about transferring some items over. Otherwise, here are a few other things to consider

  • Remove old or large files

  • Empty your Trash

  • Tidy your desktop

  • Clear your Downloads folder

This can be a time-consuming job; if you're low on time, the app I previously mentioned, CleanMyMac X, has an awesome tool called Space Lens. It gives a creative and visual overview of your Mac's storage, analyzing your system in minutes, allowing you to easily identify what items are taking up space on your Mac. 

Here's how to use Space Lens to clear your disk space:

Scan completed in Space lens module in CleanMyMacX

  1. Launch CleanMyMac X.

  2. Select Space Lens from the left sidebar and press Scan.

  3. When the scan is complete, browse through your folders, select items you want to delete, and press Remove. 

I'm a huge fan of this visual representation; the larger the bubble, the more space it occupies. I like to see the information displayed this way. It helps me decide what I need and don't. 

If storage is a real issue for you, it's worth taking some time to resolve this issue; we've got a great article on 11 ways to clear space on your Mac.

4. Use Activity Monitor to free up RAM

A shortage of RAM is a sure way to stop Photoshop in its tracks; luckily, there's a way to see what’s using most of your Mac’s resources.

Mac activity monitor

  1. Open Activity Monitor (Finder > Applications > Utilities).

  2. The most intensive processes are listed first. 

  3. If there is a process or an app you don’t need running, select it. 

  4. Click the “x” button to quit it.   

If you're still having issues, keep reading, we've got a few extra tips to work through if you are still experiencing issues with Photoshop. 

What to do if Photoshop is misbehaving 

If, after trying all of the above tips, Photoshop seems a little bit glitchy, here are a few tips to help you troubleshoot.

Disable auto-recovery saving

Photoshop, by default, is set to auto-recover your files in case of an unexpected exit. So it automatically saves recovery data every 30 seconds, creating lots and lots of temporary files. You can disable this feature completely or opt to change the save time up to 1 hour to reduce temporary files. Here's how:

Photoshop preferences

  1. Open Photoshop, from the top menu, select Photoshop > Preferences > File Handling & Clipboard.

  2. Uncheck Automatically Save Recovery Data to disable this feature or change the data recovery time by selecting the dropdown.

  3. Click Ok to save your changes. 

I find this feature a lifesaver sometimes, so as you can see, I've kept the feature and just changed the autosave to every 10 minutes. 

Reset Photoshop

Sometimes a good old reset is all you need to get things working again. 

Photoshop system files can become corrupt when the program crashes, quits unexpectedly, and stalls, so even after clearing the memory and disk space, you might experience issues. 

Luckily a quick reset will have you back up and running in no time. I like to use CleanMyMac X to manage my app resets and reinstalls; they have a dedicated Uninstaller module that quickly resets applications to their original state. Here's how:

How to reset apps on Mac

  1. Launch CleanMyMac X, select Uninstaller from the left sidebar.

  2. Select the View Applications button.

  3. Select Photoshop from the list and select Reset from the little dropdown window.

  4. Then press Reset.

Simple as that, next time you launch Photoshop, you should be trouble-free. 

The “Photoshop scratch disk full” error is frustrating, but thankfully as you can see from the tips, there are plenty of simple ways to solve it.

Storage is what it all boils down to, so remember to keep your Mac in shape by running regular maintenance, keeping on top of temporary files, cache, and other system junk, and removing old downloads.

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