How to clear scratch disk in Photoshop on Mac

If you regularly work in programs like Adobe Premiere Pro, Final Cut Pro, and Adobe Photoshop, you've probably encountered Photoshop scratch disk errors. The most common error is Photoshop's refusal to open, along with the message stating either "Could not complete your request because the scratch disks are full" or "Could not initialize Photoshop because scratch disks are full."

If you've stumbled on this page because you've experienced the full scratch disk issue, you're in luck: we're going to show you how to resolve your scratch disk problem easily and, as a bonus, keep your computer clean and performing at its best. Keep on reading to find out the following: 

  • What are scratch disks in Photoshop?
  • Why scratch disks are full?
  • How to clear scratch disk on Mac?

  • What are scratch disks in Photoshop?

    Before we highlight some solutions, it would be a good idea to have at least a general sense of what a scratch disk actually is. When you use programs like Photoshop or Final Cut Pro, they require a working space called virtual memory or cache memory. This is where temporary files are stored and accessed from.

    For this guide, we are focusing our laser sights on Photoshop. After all, it is the most common application. But rest assured that the info we cover will apply to most programs that rely on using a scratch disk.

    Scratch disk in Photoshop is your hard drive space used by the app as virtual memory when there is not enough RAM to complete a task. Photoshop allows you to assign several scratch disks: that way, it has more space for storing temporary files at its disposal.

    When working with large images and lots of layers, Photoshop is secretly chewing up your drive space by rapidly creating a mountain of project temp and cache files.

    It's important to note that when you set up Photoshop, you will have the option to assign the scratch disk to the drive of your choice. We highly recommend not using your system drive unless you have no other alternatives.


    Why scratch disks are full?

    Photoshop's temporary files are the most significant reason behind the "scratch disks are full" error. They usually mass up in your drive without leaving single evidence of their presence. If you have a habit of force-quitting Photoshop, you may have a lot of temporary files stored in your system. As Photoshop can't fully close all projects after you quit it so rapidly, it keeps such files on your computer. 

    Here are some other reasons that may cause the mentioned message:

    Lack of space

    Little space left in the drive where Photoshop's scratch disk is located

    Full disk partitionThe partition of the disk being used by Photoshop is full
    Limited RAM

    Not enough memory allowed for Photoshop


    How to clear scratch disk on Mac?

    Next, we'll explain how to clear Photoshop scratch disk and fix the scratch disc full issue on a Mac.


    1. Clear your Photoshop cache

    Photoshop has an in-built solution for deleting specific Photoshop caches. When these pesky caches aren't removed automatically by the program, they can grow and take up a lot of your disk space.

    To use this tool, simply launch Photoshop on your Mac and follow these steps with an image open:

    1. Click the Edit menu button from the menu bar.
    2. Hover your mouse over "Purge" to reveal 4 different cache categories: Undo, Clipboard, Histories, and All. Here's what they mean:
    • Photoshop records all commands you use while working on a project. Purging Undo sweeps away records about the most recently applied command. 
    • The Clipboard is a small part of memory that stores everything you copy. You can't insert copied data after you purge the Clipboard.
    • Histories contain the previous versions of your project. Purging it will remove all history states saved previously, and you won't be able to undo your latest actions. 
    • Clicking All will purge all your Photoshop cache files. 
    • Video Cache stores changes you've previously made to the video project. You won't be able to restore changes after you purge video cache.

    To clear Photoshop cache and possibly fix the scratch disks problem, choose the specific item you want to delete or select "All" to delete all of your cache files. If an item is greyed out, that means it has already been deleted.

    You will be warned that the purge cannot be undone, so make sure you don't need a previous version of one of your projects and then click OK.

      How your Scratch drive is filling up? An example from Sketch

      Along with Photoshop, Sketch is another app that keeps temporary versions of projects on your disk. And these temporary files eat up a whole lot: from 60 to 220 GB on average. Each time you press Command-S, some disk space is wasted away from your scratch disk. Say, your file weighs 23 MB. Then, 7 temporary editions would increase that size to 161 MB. Some of them are duplicate files. This problem hasn't been widely known until recently, but luckily, there is an automatic solution.  CleanMyMac's System Junk module lists Documents' Versions from Sketch and other similar apps. You can keep the final and the oldest version of a project and delete all revisions in between. Voila, you've got free disk space again and may avoid the scratch disk full error!


      2. Delete your temp files

      When it comes to your scratch disk space waste, Photoshop's own temp files are often the worst culprit. So, why store temporary files? Deleting these files may help you forget about the scratch disk full error message. Note that you may need to do it if you can't delete Photoshop's cache files, which is a rare occasion. 

      Before deleting temporary files, make sure to save your progress and close Photoshop. Now, you're ready to move on. 

      To find temporary Photoshop files:

      1. Go to Finder and click Go from the menu bar. 
      2. Here, choose Go to Folder. 
      3. Type /tmp in the field and press Enter. 

      This will open a new folder window that contains Photoshop files and folders. Now, as you see the list, carefully go through all of the folders and delete files that eat up the space of Photoshop scratch disks. Make sure you select only temporary files — those with the .tmp extension.

      Alternatively, you could also search "Photoshop Temp" with a space between the two words right in your Finder search. Following the same logic as described above, you can safely delete files and watch as your scratch disk space is reclaimed. Get rid of as many files as you can.

      Now, launch Photoshop once again. Hopefully, the scratch disk full errors are gone; if not, keep on reading to learn more tips. 


      3. Clear your disk space

      If you don't have another drive or don't want to buy one, then it's time to do some spring cleaning. Look at the drive contents to see if you can delete anything you don't need to reclaim some disk space. Is there storage space that can be cleared? Usually, there is, so go ahead and delete your old files and free up some space.

      Alternatively, you can simply transfer files to external drives, DVDs, or cloud storage solutions like Dropbox and iCloud.

      Your Mac already has the built-in tools to help you manage storage space. If you navigate to Apple Menu > About This Mac > More Info > Storage tab, you will see the storage graph.

      System Preferences - Storage

      Besides, you will see a list of recommendations. There are some truly helpful elements, such as using Optimize Storage to customize what TV shows and movies you store on your Mac and the option that allows you to view all your files, downloads, and unsupported apps. Explore the recommendations and tools to look for files you can remove to optimize your space and solve the problems with Photoshop scratch disks.

      A good way to keep Photoshop cache from piling up is by running regular disk cleanups. It will help get rid of junk files that may be causing the scratch disk error. But here is a problem: the cache sits so deep in system folders and their subfolders that deleting it manually becomes a pain. A company called MacPaw produced a tool just for this purpose, CleanMyMac X. You've heard of similar tools, but that one actually pioneered Mac cleanup.

      Here's how you can schedule regular cleanings with CleanMyMac X:

      1. Launch CleanMyMac X.
      2. Go to System Junk and press Scan.
      3. Click Review Details to deselect the data you want to keep.
      4. Hit Clean to clean up junk files.

      Just let it do its thing. That way, you'll never forget to clear Photoshop cache files and tons of other system junk on your system.

      You can download CleanMyMac X free version and see how it works.

      Tip

      If you're wondering how to fix the Photoshop scratch disk error on Mac, here's our article you might find helpful — 11 quick ways to clean your disk space. Inside, we have lots of practical tips for macOS users who want a clean drive that performs well.





      4. Change your scratch disk

      So, you've identified rapidly depleting free space on your Mac hard drive as one of the factors behind the Photoshop scratch disk problem — now what? Well, it may be a good idea to change your scratch disk to another drive in your system. Just make sure it's not the system drive, as that is one drive you really don't want to slow down. If you don't have another drive, you could purchase one, with SSD being the best option for Photoshop scratch disk purposes.

      Follow these steps to change your scratch disk using Photoshop preferences:

      1. Launch Photoshop.
      2. Go to Photoshop > Preferences from the menu bar. 
      3. Select Scratch Disks and tick the checkbox to select or remove a drive as the scratch disk.
      4. Click OK.
      5. Reopen Photoshop.

      5. Consider buying a new SSD

      As mentioned, the scratch disk problem happens because of 2 simple reasons: lack of RAM and lack of free storage space. Both can be addressed if you buy a Thunderbolt SSD (solid-state drive) to use as your Photoshop scratch disk. By today's standards, 256 GBs should be enough.

      Tip

      It can be challenging to check and analyze all contents of your disk space. Luckily, some tools can provide a disk scan and save up lots of space on your Mac. Apps notarized by Apple are best for this job. CleanMyMac X, the app I talked about earlier, has a Large & Old Files feature, which finds and removes massive files stored on your Mac. With its help, you can delete files that take up a lot of space but are actually no longer needed.


      6. Follow the 15% rule

      Not strictly a rule, but rather a common practice states that you should keep at least 10-15% of your disk space free at all times. If your storage size is 256 GB, your lower limit is 25 GB. You'll have enough room to render your Photoshop files, save multiple project copies, etc.

      Tip

      Loud fan noise is a sign your CPU is overloaded and approaching its carrying capacity. Try closing active apps you don't use to lighten the load for your Mac's CPU: press Command-Option-Esc and select unused program. Click Force Quit to quit the selected app. 


      7. Free up RAM in Terminal

      When Photoshop gets paralyzed due to lack of RAM, there is a command you can run in Terminal. 

      1. Open the Terminal app (find it in the Launchpad).
      2. Paste in: sudo purge
      3. Then, enter your password.

      At first, you may not see the difference, but you've just flushed your RAM, releasing all the files kept in virtual memory. There are a few more ways to free up RAM; check them out, too.

      You can also download CleanMyMac X (get a free edition here) and use its Free UP RAM command. 

      1. Install the app and click on Maintenance.
      2. Select Free Up RAM and click Run.

      You can apply this trick anytime to unfreeze an app. Also, check out the other tools in the Maintenance section. They will help you take some load off your Mac's memory.


      8. Reset Photoshop preferences

      Resetting Photoshop's preferences is one way to fix the "Scratch disks are full" error. Here's how to do that:

      1. Open Photoshop.
      2. Go to Photoshop preferences: from the menu bar, choose Preferences > General.
      3. In the window that appears, click "Reset Preferences On Quit."
      4. Click "OK" to confirm.

      Now, you need to quit Photoshop to complete the reset. Close the app or click Photoshop menu > Quit. Launch Photoshop once again and see if the scratch disk error message persists.


      9. Disable auto-recovery

      It's great to automatically save recovery information — it helps you make sure no progress will be lost. But if you're experiencing the "scratch disks are full" error on a Mac, disabling auto-recovery might save you some gigabytes of space. So, here's how to turn off the auto-recovery in Photoshop:

      1. Go to Photoshop menu > Preferences.
      2. Select File Handling.
      3. Uncheck the "Automatically Save Recovery Information" box.

      Now, all your progress won't be automatically saved, so don't forget to use Command-S occasionally. 


      The 'Scratch Disk Is Full' error is fixed!

      If you followed this guide, there is absolutely no reason why you should ever have to deal with the annoying "scratch disk full" error again. Next time you want to create something amazing in Photoshop, you should experience something new — a Photoshop that runs so smoothly it practically purrs.

      Whether you solve the problem yourself or let a great piece of software like CleanMyMac X do it for you, just make sure you clean up your scratch disk. Your Mac will thank you for it*.

      *Not literally. That would be weird.


      Frequently asked questions

      Why the "scratch disks are full" error may appear?

      The number one reason for the "scratch disks are full" message is the lack of space in the drive where the scratch disk is located. You can also run out of space in the partition of the disk allocated for Photoshop, which may also cause the above-mentioned error.

      What are Photoshop temporary files?

      Temporary files will appear if you don't close Photoshop fully or open the Smart Object and don't close them with the Smart Object layer. Photoshop temp files have a ".tmp" extension, so it's easy to find them on your Mac.

      How to fix the "scratch disks are full" Photoshop issue?

      One of the solutions to the scratch disk problem is to change the scratch disk allocation. You may also need to clear the Photoshop cache and remove temporary files.

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