Photoshop "Scratch Disks Are Full" Fix for Large File Saves

You're 40 minutes into a 2GB layered PSD, you hit Ctrl+S, and Photoshop throws "Could not save because the scratch disks are full." You check your C: drive — 80GB free. What gives? The scratch disk isn't your save location. It's Photoshop's temp workspace, and it's probably pointing somewhere useless or buried under years of junk files. Let's flow through this: cheapest fix first, hardest last. Stop whenever it works.

What "scratch disk" actually means

When your file plus all its history states exceed your available RAM, Photoshop spills the overflow onto disk. That disk is the scratch disk. Default is your boot drive (C: on Windows, Macintosh HD on Mac). A 2GB file with 50 history states can demand 30-50GB of scratch. If the boot drive only has 20GB free, you get this error even though Photoshop has plenty of room elsewhere.

Step 1: The 30-second fix — free up the boot drive

Quickest win. Clear the obvious junk off the drive Photoshop is using right now.

1. Open File > Save As and note the drive in the path. That's usually your scratch disk.
2. Windows: open File Explorer, right-click the drive, hit Properties. Mac: right-click the drive in Finder, then Get Info.
3. You need at least 20GB free. For files over 1GB, aim for 50GB.
4. Empty the Recycle Bin or Trash.
5. Windows only: run Disk Cleanup (search it in the Start menu), tick Temporary files and Windows Update Cleanup, hit OK. On a laptop that's been running a year, this often frees 15-30GB.

After clearing space, retry the save. If it goes through, you're done. If not, move on.

Step 2: The 5-minute fix — move the scratch disk

This is the real fix for most people. Point Photoshop at a drive that actually has room — ideally a separate SSD with 100GB+ free. Don't use an external spinning USB drive; the save will crawl.

1. Open Photoshop. Go to Edit > Preferences > Scratch Disks (Mac: Photoshop > Preferences > Scratch Disks).
2. You'll see a list of drives with checkboxes. Uncheck the full one.
3. Check a drive with at least 100GB free. SSD only.
4. Use the arrows on the right to drag your chosen drive to the top of the list.
5. Click OK. Photoshop will say the change takes effect next launch. Close and reopen it.
6. Open your file and try saving again.

If it saves, you're done. If the error persists, it's not a space problem — it's a permissions or temp-file problem. Keep reading.

Step 3: The 15-minute fix — purge stale temp files and (if needed) reset prefs

Photoshop writes scratch files as hidden temp files with names like ~PST####.tmp. If a crash left them orphaned, Photoshop thinks it has no room even when the drive is empty.

Windows

1. Close Photoshop completely. Check Task Manager — a stuck Photoshop.exe will lock the temp files.
2. Open File Explorer. Paste this into the address bar and hit Enter:
   %temp%
3. Sort by date. Delete every file starting with ~PST and anything older than today with a .tmp extension. Skip files Windows says are in use.
4. Also check C:\Users\<YourName>\AppData\Local\Temp\Photoshop if it exists. Delete its contents.
5. Reopen Photoshop and try saving.

Mac

1. Quit Photoshop. Force-quit from the Dock if it's hung.
2. Open Finder. Press Cmd+Shift+G, type /private/var/folders, hit Go.
3. In the search box top-right, type Photoshop. Delete anything matching scratch or temp files older than today.
4. Also check /tmp for files starting with Photoshop.
5. Relaunch Photoshop and retry the save.

If it still fails: reset preferences

Hold Ctrl+Alt+Shift (Windows) or Cmd+Option+Shift (Mac) while Photoshop launches. When the dialog appears, click Yes to delete the settings file. You'll lose custom workspaces and brush presets — back those up first if they matter. This fixes scratch disk errors caused by a corrupted preferences file, which is more common than Adobe admits.

Preventing it next time

• Set history states to 20, not 50. Edit > Preferences > Performance. Every history state eats scratch.
• Allocate 70-80% of RAM to Photoshop in the same panel. Leave some for the OS.
• Save as PSB, not PSD, for files over 2GB. PSD tops out and corrupts; PSB doesn't.
• Keep the scratch disk free of everything else. A dedicated 500GB SSD for scratch is the best $60 you'll spend as a retoucher.

Rule of thumb: Photoshop needs roughly 3-5x your file size in free scratch space. A 4GB PSB needs 12-20GB free minimum, more with heavy history.

Work the steps in order. Most people are fixed at Step 2. If you're still stuck after Step 3, the drive itself is probably failing — run a SMART check with CrystalDiskInfo on Windows or Disk Utility's First Aid on macOS before you blame Adobe.