How to Clear the Scratch Disk in Photoshop

If you’ve used Pho­to­shop for any amount of time, you’ve prob­a­bly encoun­tered the dread­ed “scratch disk is full“ error at least once. This error can even stop you from open­ing the app and occurs in all ver­sions of Pho­to­shop on both Win­dows and Mac. It’s fre­quent­ly encoun­tered when increas­ing image res­o­lu­tion in Pho­to­shop or try­ing to load too many images at once. Here’s how you can clear the scratch disk in Pho­to­shop to free up space.

Pho­to Cred­it: Goumbik via Wun­der­stock (license)

What is a scratch disk?

A scratch disk is a stor­age area on your Mac or Win­dows com­put­er that’s used as tem­po­rary stor­age for Pho­to­shop– tem­po­rary set­tings, cropped pix­els, etc, when there is not enough space in your RAM. Often the size of the Pho­to­shop needs for the scratch disk can fluc­tu­ate wild­ly based on what you are edit­ing. Pho­to­shop thus needs ample disk space to run smoothly.

Even if you don’t see a scratch disk full error, you may need to emp­ty the scratch disk or increase its size if Pho­to­shop becomes too slow. You may for exam­ple notice that zoom­ing in and zoom­ing out feel choppy.

How to clear your Photoshop scratch disk

Fix­ing the “scratch disk full” error is most­ly a mat­ter of free­ing up disk space. Below is our rec­om­mend­ed way to do this on Win­dows and Mac computers:

Step 1: Purge the Photoshop cache

Pho­to­shop should auto­mat­i­cal­ly clear the cache peri­od­i­cal­ly, but some­times a man­u­al purge is necessary. 

If you can still access Pho­to­shop, open an image in the pro­gram and nav­i­gate to the “Edit” menu on the top of the screen. Go to “Purge” and click “All” to remove cached files from the scratch disk. If these items appear greyed out, this means that there are no cached items to delete.

On Mac, you can do the same thing by nav­i­gat­ing to Pho­to­shop CC -> Purge -> All

Step 2: Delete temporary files

Delet­ing tem­po­rary files is pret­ty fast and easy.

Pho­to­shop will some­times leave a rather large assort­ment of tem­po­rary files sit­ting around on your hard disk. Remov­ing them will free up space for both your scratch disk and oth­er pro­grams on your computer. 

This is also the first step you should take if you want to clear the scratch disk with­out open­ing Photoshop. 

Deleting Photoshop temp files on Mac:

  1. Go to Terminal
  2. Type “open / tmp”
  3. Delete all files start­ing with “Pho­to­shop Temp”

Deleting Photoshop temp files on Windows:

  1. Open File Explorer
  2. Nav­i­gate to C:\Users\Your User­name\AppData\Local\Temp
  3. Delete all files start­ing with “Pho­to­shop Temp”

You can also search your com­put­er for “Pho­to­shop Temp”. You can also search for files that begin with “pst” or end in “.tmp”, Be sure to include hid­den files and fold­ers in your search.

Step 3: Allocate more memory to Photoshop

Allow­ing Pho­to­shop to use more mem­o­ry will improve per­for­mance, but will slow down oth­er appli­ca­tions run­ning simultaneously. 

Pho­to­shop will first try to use your mem­o­ry (RAM) before allo­cat­ing data to the scratch disk. Allow­ing the pro­gram to use more mem­o­ry can improve per­for­mance and pre­vent it from hav­ing to ever go near the scratch disk in the first place.

To do this on Win­dows, go to Edit -> Pref­er­ences -> Per­for­mance. On Mac, sim­ply go to Pho­to­shop CC -> Pref­er­ences -> Per­for­mance. Nav­i­gate to Mem­o­ry Usage. Move the slid­er to increase RAM access. 

RAM is much faster to access than your hard disk. Con­sid­er upgrad­ing your com­put­er with more mem­o­ry to boost per­for­mance in Pho­to­shop if scratch disk access becomes a fre­quent issue.

Step 4: Add a scratch disk or change your scratch disk

You can also add a new scratch disk if you have an exter­nal hard dri­ve or anoth­er par­ti­tion. To do this on Win­dows, go to Edit -> Pref­er­ences -> Per­for­mance. On Mac, go to Pho­to­shop CC -> Pref­er­ences -> Per­for­mance. Nav­i­gate to Scratch Disks. From this menu you can choose a new scratch disk.

From here you will have to restart Pho­to­shop for the change to take effect.

On Mac, you can also press “Command+Click” when launch­ing Pho­to­shop to man­u­al­ly choose a new scratch disk.

Can I use an external hard drive as the scratch disk in Photoshop?

Absolute­ly! You can use the steps above to select any exter­nal hard dri­ve as the scratch disk in Pho­to­shop. Keep in mind that depend­ing on the spec­i­fi­ca­tions of the hard dri­ve, you may suf­fer degrad­ed per­for­mance. USB‑C and Thun­der­bolt dri­ves, espe­cial­ly SSDs, should work very well. 

Old­er USB and Firewire dri­ves will per­form slow­ly and are prob­a­bly not worth using as a scratch disk.

Other solutions for the “scratch disk full” error

The stan­dard advice for free­ing up space on your com­put­er also applies here. Emp­ty your Trash / Recy­cle Bin to remove unused files. Delete any unneed­ed pro­grams. On Win­dows, you can also defrag­ment your hard dri­ve. Close any oth­er open files, includ­ing oth­er Pho­to­shop images, and pro­grams to free up space.

It may also be that the file you are work­ing with is sim­ply too large. You’re less like­ly to encounter the “scratch disk full” error when work­ing with small­er files. Con­sid­er if you real­ly need to be work­ing with such a large image and if not, make the can­vas area small­er to free up resources. 

If all else fails and you keep encoun­ter­ing scratch disk issues on your com­put­er, your work may have out­grown your com­put­er. It may very well be time to upgrade your PC or MAC for bet­ter per­for­mance, espe­cial­ly if it is already 4+ years old and you are work­ing with espe­cial­ly large files. Or you might want to con­sid­er a Pho­to­shop alter­na­tive that has low­er sys­tem requirements.

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