Designers · problem and fix
Photoshop scratch disks are full Mac error: causes and fixes for designers in 2026
When Photoshop says scratch disks are full on a Mac, its temporary working file has no room left. Free space on your startup disk first, then purge Photoshop's cache and lower the history states. These fixes need no new purchase. Here is the order that works, what the warning costs you, and why it keeps coming back.
The short answer
- Photoshop writes overflow to a scratch file on the startup disk when RAM runs short.
- Free space on Macintosh HD first. Mole reports Adobe recommends at least 100 GB free on the primary scratch disk.
- Then run Edit > Purge, lower the history states, and check the scratch disk list in Photoshop > Settings.
- Use a second drive only if it is APFS or Mac OS Extended (Journaled) and fast.
- Check Trash and Time Machine snapshots too, since they can hide space you think is free.
What scratch disk full error on mac costs you
Lost time, in plain numbers
A 2023 study of general computer users found machines malfunction 11 to 20 percent of the time. The study ran in ACM Transactions on Computer-Human Interaction. It did not look at designers or scratch disks. Apply the same share to one hour of work and you lose 6.6 to 12 minutes. At the BLS median of $30.27 an hour, that is about $3.33 to $6.05 of wage time per hour. That is my arithmetic from those two sources, not a figure either one reports.
Late files and rushed exports
A warning that stops a save or an export puts pressure on the deadline. You may send a rushed file, or skip the version you wanted. Clients see the late file, not the cause. Fix the disk before deadline week, not during it.
Lost unsaved work
When Photoshop quits in the middle of a full disk, unsaved steps can vanish. Save a working copy before big operations. Keep your source files somewhere else. The scratch file is temporary, so it is not a backup of anything.
Money spent on the wrong fix
Buying more cloud space does not fix scratch. Apple lists iCloud+ at $2.99 a month for 200 GB and $9.99 a month for 2 TB. That moves files off your Mac. It does not change where Photoshop writes its scratch file, so buy storage only after you know what fills the disk.
Why it happens
The startup disk is nearly full
Macintosh HD holds macOS, apps, your photos, downloads, caches, and System Data. Photoshop's scratch file competes with all of it. A Mac with a few large project folders and a stack of old installers can reach the limit quickly. Mole says the primary scratch disk should keep at least 100 GB free.
Photoshop skips the drive you picked
Photoshop only accepts APFS or Mac OS Extended (Journaled) volumes as scratch disks. An Adobe Community answer marked correct says the same, based on Adobe's help article. Mole adds that exFAT drives do not appear in the list. A drive in the wrong format gets skipped, so the startup disk fills up instead.
The RAM allowance is too small for the file
Photoshop uses RAM first. Mole says memory allocation defaults to 70 percent, and that Adobe advises against going above 85 percent. A large document with a low allowance spills to disk sooner. The scratch file then grows with every layer and step.
History states and undo steps pile up
Each history state adds to the working data Photoshop keeps. Mole suggests lowering history states from 50 to about 20 to 30 when space is short. Long sessions with many steps make the scratch file grow faster than short ones.
Caches and temporary files stick around
MacPaw says Photoshop creates temporary and cache files, and that they can persist after a force quit. Other Creative Cloud apps add media caches on the same disk, according to Mole. Those files take space long after the session that made them has ended.
Trash and snapshots hide space
Trash space is not free until you empty it, according to Apple. A 2022 developer forum post reported about 660 GB held by Time Machine local snapshots on macOS 12.4. That is one user report, not an Apple statement, so check your own storage breakdown before you act on it.
How to fix it
These work with or without any app.
Free the startup disk first
On macOS Ventura 13 or later, open Apple menu > System Settings > General > Storage. On older macOS, use About This Mac > Storage. Open the largest categories and remove what you do not need. Apple suggests emptying Downloads, deleting unused apps, and removing old iPhone or iPad backups.
Empty the Trash for real
Trash space does not count until you empty the Trash, according to Apple. Choose Finder > Empty Trash. In the Storage settings you can also turn on Empty Trash automatically. Apple says that option erases items that have been in the Trash for more than 30 days.
Turn on Optimize Storage with care
Optimize Storage removes Apple TV shows and movies you have already watched. When space is needed, it keeps only recent email attachments on the Mac. macOS also clears caches and logs that are safe to delete. Read the recommendations before you accept them, and keep anything you still need.
Purge Photoshop's cache
Save your open work, then choose Edit > Purge. MacPaw says purge cannot be undone, so pick only the items you can give up. Purging clears undo history and cached data. The next session starts with less of the disk taken up by old working data.
Lower the history states
Open Photoshop > Settings > Performance. Older guides call this Photoshop > Preferences, so check your version. Set History States lower. Mole suggests moving from 50 to about 20 to 30. Fewer states means less undo, so pick a number you can work with.
Fix the scratch disk list
Open Photoshop > Settings > Scratch Disks. Put the drive with the most free space and the best speed at the top. MacPaw advises against using the system drive as the scratch disk, so a second drive helps if you have one. Check the Efficiency number afterward to see whether the change helped.
Use a drive you already own
The scratch drive must be APFS or Mac OS Extended (Journaled). exFAT drives do not show up in the list. MacPaw recommends an SSD over a hard disk, and says 256 GB should be enough for a scratch drive. Formatting a drive erases everything on it, so check that it is empty first.
Read the Efficiency number
Photoshop shows an Efficiency readout in the document window's status bar. Mole says a value below 95 percent means the scratch disk is in use. Use it as a check after each fix. If the number stays low, the disk space or the RAM setting still needs work.
Check Time Machine snapshots only if they are large
Local snapshots can hold space. In Terminal, run tmutil listlocalsnapshotdates to list them. Delete one with tmutil deletelocalsnapshots followed by its date. Snapshots are restore points, so remove only the ones you do not need. One forum post reports this worked on macOS 12.4, so check current Apple documentation first.
What the scratch disks are full message means
Photoshop keeps your open document, layers, history states, and caches in RAM. When RAM runs short, it writes the overflow to a scratch file on disk. That scratch file is what the warning is about.
On most Macs, that disk is Macintosh HD. It also holds your apps, photos, downloads, and System Data. The free space you see in Finder is shared with all of it, and Photoshop has to compete for it.
The warning is a limit, not a crash. Photoshop cannot grow its working file past the free space it can find. You may see slowdowns, so save early and free space before you keep working.
11 to 20%
of computer time lost to malfunctions, in a study of general users, not designers
EurekAlert: We are wasting up to 20 percent of our time on computer problems$30.27
median hourly wage for graphic designers, May 2025
BLS Occupational Outlook Handbook: Graphic Designers100 GB
free space Mole says Adobe recommends on the primary scratch disk
Mole: How to Fix the Photoshop Scratch Disks Are Full Error on MacCheck the number before you change anything
The number that matters is free space on the startup disk, not the size of the drive. Mole reports that Adobe recommends at least 100 GB free on the primary scratch disk. Other guides quote different figures, so check Adobe's current help pages before you plan around one number.
Say Macintosh HD shows 60 GB free. Against Mole's 100 GB figure, you are 40 GB short. Clearing 40 GB only gets you to the line. Aim a little past it, because caches grow again as soon as you open a large file.
Clear the things that stay gone first. Old installers, finished exports, and forgotten downloads rarely come back. Caches do. Plan for both, or the warning comes back quickly.
Work the list in this order
- Empty the Trash, then read the free space again. Trash space does not count until it is gone.
- Delete old installers, finished exports, and downloads you no longer need. Open the largest categories on the Storage page first.
- Save your work, then run Edit > Purge to clear the open document's cache.
- If the file is still too large, lower the history states in Photoshop > Settings > Performance.
- Set Photoshop > Settings > Scratch Disks so the fastest drive with room comes first.
Mistakes people make with scratch disks
- Pointing the scratch disk at a second drive that is also nearly full. Two full disks do not help.
- Choosing exFAT for an external drive. Mole says exFAT drives do not show up in Photoshop's list.
- Trusting the Finder free space number before you empty the Trash.
- Deleting Time Machine snapshots without checking whether you need the restore points.
- Keeping very high history states for safety. The file grows faster when Photoshop records more steps.
- Treating one clean-up as permanent. Caches and downloads fill the disk again.
Where Lazur helps with this warning
Lazur is a voice assistant for the Mac, and it lives in the notch. Hold ⌥ ⌘ to ask about anything on screen. Lazur answers out loud. That helps when a warning box is open and you need the next step without digging through menus.
Lazur points, explains, and guides. It does not click buttons, change Photoshop settings, or edit files for you. Ask where the Scratch Disks setting is, and Lazur draws a circle and a label around it. Ask how to purge, and Lazur guides you one click at a time, waiting for each click.
For Adobe's current guidance, ask Lazur to research it. Research runs in Lazur's own Chrome tabs and comes back with a summary and a report. Check Adobe's page yourself before you act on any number in that report.
Privacy and client files
Lazur listens and looks at the screen only while you hold the shortcut. Audio and the screenshot go to AI providers to answer, and they are not stored. Content is never used to train AI models. That still does not decide what your client allows. Check your studio or client agreement before you share screenshots of client work with any tool.
When the fix does not stick
Sometimes the warning returns within a day. Usually a cache or a large download did it. Check the Downloads folder, the Photoshop cache, and the media caches from other Creative Cloud apps. Mole lists Lightroom Classic previews and Premiere Pro and After Effects media cache as common space hogs.
If the disk stays tight, reduce what you open at once. Flatten layers you no longer edit, and crop to the final size before you start a new round of work. Keep finished projects on a drive you own, following your studio's rules for client files.
Use a second drive only if it is APFS or Mac OS Extended (Journaled) and fast. MacPaw recommends an SSD over a hard disk. A slow drive stops the warning but slows every stroke you make.
Faster with Lazur
Where Lazur helps with scratch disk full error on mac
Hold ⌥ ⌘ and say what you want. Lazur sees your Photoshop window. Lazur draws a circle and a label around the button or menu you need.
- 1
Hold ⌥⌘ and talk
- 2
Lazur draws a circle and a label around the button or menu you need.
- 3
You stay in Photoshop. Nothing to copy into a chat window.
More things to say in Photoshop
- “Where is the Scratch Disks setting in Photoshop?”
- “Why did Photoshop say my scratch disks are full?”
- “Walk me through purging the cache, one click at a time.”
- “Find Adobe's current scratch disk guidance and summarize it.”
- “Remind me to empty the Trash on Friday.”
- “Note which drive I picked as the scratch disk today.”
Free for 3 days, then $18/month. Download for Mac
You say“Where are my scratch disk settings in Photoshop?”
Lazur · points at itLazur circles the Scratch Disks area and labels it. You make the change yourself, one field at a time.
What designers say to Lazur for this
Each one is a single hold of ⌥ ⌘.
“Where is the Scratch Disks setting in Photoshop?”
Lazur draws a circle and a label around the setting on your screen, so you can find it and change it yourself.
Points at it
“Why did Photoshop say my scratch disks are full?”
Lazur answers out loud, based on what is on your screen, such as the warning box and the Efficiency readout.
Explains what's on screen
“Walk me through purging the cache, one click at a time.”
Lazur guides you one click at a time and waits for each click, so you decide what gets purged.
Walks you through it
“Find Adobe's current scratch disk guidance and summarize it.”
Research runs in Lazur's own Chrome tabs and returns a summary and a report for you to check.
Researches in the background
“Remind me to empty the Trash on Friday.”
Lazur adds the reminder to Apple Reminders by voice, so the habit shows up on your list.
Handles the small stuff
“Note which drive I picked as the scratch disk today.”
Hold fn and speak. Dictation types clean text at the cursor, in any app, which helps you keep a fix log.
Types what you say
A plan you can start this week
- Today
Free the startup disk
Open Apple menu > System Settings > General > Storage. Remove large files you no longer need. Empty the Trash, then read the free space again. Check the Efficiency readout on your open file afterward.
- Day 2
Set scratch disks and history
Open Photoshop > Settings > Scratch Disks and confirm the order. Lower the history states in Performance if you rarely need deep undo. Save your work first, then run Edit > Purge if the warning returns.
- Day 3
Test a big file
Open your largest working file and do a normal session. Watch the Efficiency readout as you work. If it drops below 95 percent, note the file size and the drive you were using.
- Weekly
Review Storage and snapshots
Once a week, open the Storage page in System Settings and read what macOS suggests. If you use Time Machine, decide whether local snapshots need clearing before you delete anything.
- Monthly
Move finished projects off the Mac
Move finished client projects to an external drive you own or to cloud storage. Follow your studio's rules for client files. Keep only the active project on the startup disk, so it has room.
- Ongoing
Keep a short fix log
Write down the date, the drive, the free space, and what you cleared. Dictate the note with fn if that is faster. A short log shows which habit actually keeps the warning away.
Questions people ask
Why does Photoshop say scratch disks are full on my Mac?
Photoshop writes overflow to a scratch file when RAM runs out. That file sits on a disk, and on most Macs that disk is Macintosh HD, which also holds apps, photos, and System Data. Free space on that disk, or point scratch at another drive, and the message usually stops.
How much free space does Photoshop need on the scratch disk?
Mole reports that Adobe recommends at least 100 GB free on the primary scratch disk. Other guides quote different figures, so check Adobe's help pages for the current number. MacPaw says 256 GB should be enough for a scratch drive.
Can I use an external drive as a Photoshop scratch disk?
Yes, if it is formatted as APFS or Mac OS Extended (Journaled). An Adobe Community answer, marked correct, says both formats are supported. Mole says exFAT drives do not appear in the list. MacPaw recommends an SSD over a hard disk for speed.
Will Edit > Purge delete my saved files?
Purge clears undo history and cached data, so save your open work before you run it. MacPaw says purge cannot be undone. Pick only the items you can give up, and keep your source files backed up somewhere else.
Why is my free space still low after I empty the Trash?
Apple says Trash space stays unavailable until you empty the Trash. Local Time Machine snapshots can also hold space. One Apple Developer Forums post reported about 660 GB held this way on macOS 12.4. Check your own storage breakdown before you delete anything.
Does iCloud fix the scratch disk warning?
No. iCloud+ moves files off your Mac. It does not change where Photoshop writes its scratch file. Apple lists the 200 GB plan at $2.99 a month and the 2 TB plan at $9.99 a month. Use it to free space for files, then recheck the startup disk.
Should I lower my history states?
Only if the warning keeps coming back. Mole suggests lowering history states from 50 to about 20 to 30 when space is short. Fewer states means less undo, so choose a number you can work with.
Can Lazur fix this for me?
No. Lazur does not click buttons or change Photoshop settings for you. It can point at the Scratch Disks area, explain the warning out loud, and guide you one click at a time, waiting for each click.
Sources
- Apple Support: Free up storage space on Mac · Apple · checked 2026-11-08
- Apple Support Guide: Optimize storage space on your Mac · Apple · checked 2026-11-08
- Apple iCloud+ · Apple · checked 2026-11-08
- BLS Occupational Outlook Handbook: Graphic Designers · U.S. Bureau of Labor Statistics · checked 2026-11-08
- EurekAlert: We are wasting up to 20 percent of our time on computer problems · EurekAlert · checked 2026-11-08
- Adobe Community: What format for external hard drive for Photoshop scratch disk · Adobe Community · checked 2026-11-08
- Mole: How to Fix the Photoshop Scratch Disks Are Full Error on Mac · Mole · checked 2026-11-08
- MacPaw: How to clear scratch disk in Photoshop on Mac · MacPaw · checked 2026-11-08
- Apple Developer Forums: Purgeable User Space Issue and Time Machine Local Snapshots · Apple Developer Forums · checked 2026-11-08
Fix scratch disk full error on mac with Lazur, free for 3 days
Hold a key and ask. Lazur sees your screen, points at the button and talks you through it, in any Mac app. No credit card.