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marti.montilla
November 25, 2025
Answered

scratch disk is full

  • November 25, 2025
  • 4 replies
  • 825 views

I’m having serious problems with storage on my iMac, especially with how Adobe apps manage everything they save. My internal disk is almost full, but I have an external drive with 2 TB of free space. My goal is to make absolutely everything Adobe generates (caches, previews, projects, downloads, temporary files, scratch disks, proxies, etc.) go directly to the external disk — because my internal disk has no space left.

I tried moving the Adobe apps to the external drive, but I understood that they must be installed in the internal Applications folder, otherwise they don’t work. So I kept them there.

I also set the scratch disks and project locations to the external drive, but I’m not sure if EVERYTHING is actually being saved there. It feels like some files still go to hidden system folders like Library, Caches, Temporary Items, etc. Even when I delete all caches and scratch disks, Photoshop still shows the error: “Scratch Disk is too full.” Illustrator also gives me doubts, and After Effects won’t let me save projects in the external drive at all – only iCloud or the internal disk.

Sometimes I even find old files in Library or system folders that I deleted a long time ago. It’s like something keeps generating data in the background that I can’t see or control.

What I really need to know is:

  • Is there ANY way to force Adobe to save everything to the external disk?

  • Do I need to format or partition the disk in a specific way for Adobe to use it correctly?

  • Does Adobe automatically store files I can’t see? How can I find them?

  • How can I configure projects, proxies, caches, previews, scratch disks, and downloads to go ONLY to the external disk?

  • If the scratch disks are correctly set to the external drive, why does Photoshop still say the disk is full?

I feel very lost about how Adobe uses system storage and what it keeps creating without my knowledge. I need guidance to fully clean Adobe files and prevent it from using my internal drive.

Any help would be extremely appreciated. I use these apps for work and my computer is always at the storage limit.

Thank you!

Correct answer Conrad_C
quote

 My internal disk is almost full, but I have an external drive with 2 TB of free space.

By @marti.montilla

 

When you say “almost full,” how full is that internal volume?

 

The reason I ask is if it has more than (very roughly) 50GB of free space, and if all applications are directed to save temporary files to the external volume, it should work. Much more free space is preferred, though.

 

But the closer the internal volume free space is to 0GB of free space, the higher the risk that some mandatory temporary files  from various Adobe, Apple, and other apps just won’t have room and you will have major problems as well as internal storage slowing down dramatically.

 

Also, in recent versions of macOS, Photoshop may report a much lower amount of free space than the macOS Finder. This is related to how macOS counts free space on volumes formatted as APFS. When the amounts of free space are different, for scratch disks you have to go by what Photoshop thinks is free space even if the Mac thinks there is more. (The explanation why would take a few more paragraphs, or you can just read this article.)

quote

Even when I delete all caches and scratch disks, Photoshop still shows the error: “Scratch Disk is too full.”

By @marti.montilla

 

When you look at the Scratch Disks list in Photoshop preferences, have you verified that your 2TB external volume is properly set up? What I specifically mean by that is:

  • The external volume is enabled in the “Active?” column in the list. (If it can’t be enabled, it may be formatted using an incompatible file system.) 
  • The external volume is at the top of the list. (If the system volume is still at the top of the list, Photoshop will use that first. Always use the up/down sort buttons to put the preferred scratch disk at the top of the list, and the volume with the least free space at the bottom of the list.) 

 

According to the Adobe help article Troubleshoot scratch disk full errors in Photoshop, if you want to use a drive as a scratch disk for Mac Photoshop, it needs to be formatted as APFS (highly preferred for best performance on SSDs) or HFS+ (OK for HDDs). 

quote

What I really need to know is:

  • Is there ANY way to force Adobe to save everything to the external disk?

  • How can I configure projects, proxies, caches, previews, scratch disks, and downloads to go ONLY to the external disk?

By @marti.montilla

 

When multiple Adobe apps are involved, sadly there is no easy or unified way because the apps work very differently. Unfortunately, we have to manually check all of the settings ourselves. For example, I use Photoshop, Lightroom Classic, Bridge, Premiere, After Effects, and more. So, on my MacBook Pro I have to (and yes this is a hassle) regularly keep an eye on the locations and sizes of these possibly large file caches:

  • Photoshop scratch disk
  • Camera Raw Cache 
  • Bridge cache 
  • Lightroom Classic video cache 
  • Lightroom Classic previews cache  
  • Lightroom Classic local import and cloud download locations
  • Premiere/After Effects Media Cache (large amounts of very fast free space is extremely important for maximum performance)

(not a complete list)

 

Another major hassle I run into: I don’t know if it’s just me, but I frequently need to check to make sure the Adobe Media Cache is still set to my external SSD. For some reason, Premiere/After Effects love to forget the setting and revert to my MacBook Pro internal storage where there isn’t enough room for the size that cache deserves (ideally several hundred GB).

 

Keep in mind that even if you solve for Adobe, Apple macOS itself constantly needs to create its own temporary files for many reasons (Time Machine local snapshots, sleep cache image, virtual memory swap…), so ultimately, the solution is to get enough stuff off that internal storage so that it ideally has 100GB or more free at all times to avoid problems in general (not just with Adobe apps). 

4 replies

Conrad_C
Community Expert
Conrad_CCommunity ExpertCorrect answer
Community Expert
December 5, 2025
quote

 My internal disk is almost full, but I have an external drive with 2 TB of free space.

By @marti.montilla

 

When you say “almost full,” how full is that internal volume?

 

The reason I ask is if it has more than (very roughly) 50GB of free space, and if all applications are directed to save temporary files to the external volume, it should work. Much more free space is preferred, though.

 

But the closer the internal volume free space is to 0GB of free space, the higher the risk that some mandatory temporary files  from various Adobe, Apple, and other apps just won’t have room and you will have major problems as well as internal storage slowing down dramatically.

 

Also, in recent versions of macOS, Photoshop may report a much lower amount of free space than the macOS Finder. This is related to how macOS counts free space on volumes formatted as APFS. When the amounts of free space are different, for scratch disks you have to go by what Photoshop thinks is free space even if the Mac thinks there is more. (The explanation why would take a few more paragraphs, or you can just read this article.)

quote

Even when I delete all caches and scratch disks, Photoshop still shows the error: “Scratch Disk is too full.”

By @marti.montilla

 

When you look at the Scratch Disks list in Photoshop preferences, have you verified that your 2TB external volume is properly set up? What I specifically mean by that is:

  • The external volume is enabled in the “Active?” column in the list. (If it can’t be enabled, it may be formatted using an incompatible file system.) 
  • The external volume is at the top of the list. (If the system volume is still at the top of the list, Photoshop will use that first. Always use the up/down sort buttons to put the preferred scratch disk at the top of the list, and the volume with the least free space at the bottom of the list.) 

 

According to the Adobe help article Troubleshoot scratch disk full errors in Photoshop, if you want to use a drive as a scratch disk for Mac Photoshop, it needs to be formatted as APFS (highly preferred for best performance on SSDs) or HFS+ (OK for HDDs). 

quote

What I really need to know is:

  • Is there ANY way to force Adobe to save everything to the external disk?

  • How can I configure projects, proxies, caches, previews, scratch disks, and downloads to go ONLY to the external disk?

By @marti.montilla

 

When multiple Adobe apps are involved, sadly there is no easy or unified way because the apps work very differently. Unfortunately, we have to manually check all of the settings ourselves. For example, I use Photoshop, Lightroom Classic, Bridge, Premiere, After Effects, and more. So, on my MacBook Pro I have to (and yes this is a hassle) regularly keep an eye on the locations and sizes of these possibly large file caches:

  • Photoshop scratch disk
  • Camera Raw Cache 
  • Bridge cache 
  • Lightroom Classic video cache 
  • Lightroom Classic previews cache  
  • Lightroom Classic local import and cloud download locations
  • Premiere/After Effects Media Cache (large amounts of very fast free space is extremely important for maximum performance)

(not a complete list)

 

Another major hassle I run into: I don’t know if it’s just me, but I frequently need to check to make sure the Adobe Media Cache is still set to my external SSD. For some reason, Premiere/After Effects love to forget the setting and revert to my MacBook Pro internal storage where there isn’t enough room for the size that cache deserves (ideally several hundred GB).

 

Keep in mind that even if you solve for Adobe, Apple macOS itself constantly needs to create its own temporary files for many reasons (Time Machine local snapshots, sleep cache image, virtual memory swap…), so ultimately, the solution is to get enough stuff off that internal storage so that it ideally has 100GB or more free at all times to avoid problems in general (not just with Adobe apps). 

    PECourtejoie
    Community Expert
    PECourtejoieCommunity Expert
    Community Expert
    December 5, 2025

    Hi, how did you format the external disk? Donor use EXFAT , only transfer disks between pc and Mac's should use that.

     

    smart objects default to using the startup disk.

    D Fosse
    Community Expert
    D FosseCommunity Expert
    Community Expert
    November 25, 2025

    Every application you ever use, every process in the operating system, will store data on your system drive. That's what the system drive is for. Some of it temporary, some permanent. Your user account continually grows over time as you use the machine.

     

    What is special about Photoshop is that it handles particularly big chunks of data. That's the nature of raster image files. They are just big, and that's why Photoshop uses a scratch disk. But the scratch disk isn't all. The graphics processor in a Mac uses shared system memory, and it can use a lot, performing advanced tasks on behalf of Photoshop. When system memory runs low, the GPU (and the whole system) starts writing to the pagefile on the system drive. Smart objects will also store temp data in the system pagefile.

     

    Until you can clean out your drive, which you have to do, there are a few things you can do. First and foremost, reduce history states, if necessary all the way down to 1. That means you can't go back, but this will dramatically reduce the size of the scratch file. Also watch the number of files you have open simultaneously.

     

    Second, if you use Bridge, move the Bridge cache. If you have a sizable archive, the Bridge cache can grow to, say, 20-50 GB, and by default it's on the system drive. The same goes for Premiere Pro if you have that. The Camera Raw cache can be a couple of GB as well. They can all be moved.

     

    As a general rule of thumb, a standard configuration of operating system and a normal range of apps including CC, should not take up more than 100-130 GB. If it grows significantly beyond that, you can assume that a lot of stuff/junk has accumulated in your user account (that's where it all goes). A lot of it can be removed with no ill effect, as long as you leave the actual operating system user folder alone.

     

    There are utilities that can show you in a graphical interface exactly what fills up your drives and exactly where it is. I'm not up to speed on what's available for Mac. But start by running a standard disk cleanup in your operating system, that can be surprisingly effective.

    E
    ExUSA
    Legend
    November 25, 2025

    OmniDiskSweeper or Grand Perspective, similar to WinDirStat on Windows.

      E
      ExUSA
      Legend
      November 25, 2025

      I'd start here:

      https://helpx.adobe.com/photoshop/desktop/troubleshoot/troubleshoot-tools-resources/set-up-and-manage-scratch-disks.html

      But understand that both Apple and Adobe will use the startup drive for both temp and permanent storage. macOS uses scratch disk space similar to Photoshop. You REALLY want to clear space on the internal drive because you'll end up with crashes or data loss.

      A second external drive can typically be had for under US$100 (Black Friday sales!) and would also give you space for backups.

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