If you are a macOS user who regularly works in programs like Adobe Premiere Pro, Final Cut Pro, and Adobe Photoshop, you’ve probably encountered errors relating to a 'scratch disk.' The most common error is Photoshop’s refusal to open along with the message 'could not initialize Photoshop because the scratch disks are full'.
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Since Mac OS 10.7, Apple has also included a built-in tool to view both free disk space and detailed disk usage that can be accessed through the “About This Mac” window. Here’s how to see it. First, click on the “Apple” menu in the upper-left corner of the screen and select “About This Mac.”. The Info window shows the capacity, available space, and used space, as well as other information. Option 4: About This Mac In recent versions of macOS (Yosemite or later), you can easily check.
If you’ve stumbled on this page because you’ve experienced this issue, you’re in luck: we’re going to show you how to easily resolve your scratch disk problem and, as a bonus, keep your Mac clean and performing at its best.
What is a scratch disk?
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 are using programs like Photoshop or Final Cut Pro, they require a working space called virtual memory or cache memory. This is where temporary project files are stored and accessed.
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 scratch drives.
Scratch disk is your hard drive space used by Photoshop 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 at its disposal.
When working with large images and lots of layers, Photoshop is secretly chewing up your Mac’s space by rapidly creating a mountain of project temp files.
It’s important to note that when you set up Photoshop, you will have the option to assign the scratch disks to the drive of your choice. We highly recommend not using your system drive, unless you have no other alternatives.
Reasons behind “scratch disks are full” error
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 on your Mac. As Photoshop can’t fully close all projects after you quitted it so rapidly, it keeps such files on your machine.
Here are some other reasons that may cause the mentioned message:
- Lack of space in the drive where the scratch disk is located
- The partition of the disk being used by Photoshop is full
- Limited RAM allowed for the Photoshop
What to do when your scratch disks are full?
Mac users receive a 'scratch disk full' message when Photoshop (or any of the other programs) has used up all the space on the hard drive that has been assigned as a scratch disk. This used up space is temporary and separate from your actual project file.
The problem is that Photoshop doesn't always get rid of these temporary files when they aren't needed anymore, which is more like a permanent problem if the user can't find a solution.
So how to clear your scratch disks? Let's find out.
Important takeout: If your HD is full, Photoshop will display scratch disk errors.
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 space on your scratch disk.
To use this tool simply enter Photoshop in Mac and with an image open:
- Click the Edit menu button.
- Hover your mouse over 'purge' to reveal 4 different options.
- Undo, Clipboard, Histories, All. If an item is greyed out, that means it has already been deleted.
- Select the specific item you want to delete or select 'all' to delete all of your caches.
- 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.
A good way to keep Photoshop cache from piling up is running regular disk cleanups. 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:
- Launch CleanMyMac X tool.
- Click System Junk and press Scan.
- Click Review Details to deselect the data you want to keep.
- Hit Clean to clean up junk files.
Just let it do its thing. That way, you’ll never forget to clear Photoshop cache and tons of other system junk on your system.
You can download CleanMyMac X free version and see how it works.
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 it eats up a whole lot: from 60 to 220 GB on average.
Each time you press Command + S some space is wasted away from your Scratch drive. Say, your file weighs 23 mb. Then, 7 temporary editions would increase that size to 161 MB. 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 space again!
2. Delete your temp files
When it comes to wasting space on your scratch disk, the worst culprit is often Photoshop's own temp files. If Photoshop isn't going to get rid of them, I guess you’re going to have to do the job yourself.
To find them you'll need to look for files that begin with 'pst' and then a string of numbers followed by the file extension '.tmp'. Do a search for 'Photoshop Temp' with a space between the two words.
You can just search your scratch drive but to make sure everything is found, rather perform the search on the entire computer. It may take a couple of minutes for the search to complete, so pop into the kitchen for a quick snack while you wait.
When you return, you should have a long list of files. If your work is saved and the program is closed, you can safely delete these files and watch as your scratch disk space is reclaimed.
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. 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.
Take a look at our How to Clean Your Startup Disk (10 Ways). Inside we have lots of practical advice for macOS users who want a clean drive that performs well. Even if your scratch disk isn’t your startup drive, and we hope that is the case, there are many tips to help you spring clean like a pro.
Notice for macOS Sierra (and higher) users:Users of macOS Sierra might be aware that Apple has added new tools to 'help' manage storage space. If you navigate to Apple Menu > About This Mac > Storage tab you will see the new Sierra bar graph.
If you click on 'manage' you will be taken to the new tools. While there are some truly helpful elements, like using Optimized Storage to customize what email attachments download to your Mac, most of the tools just move junk from one place to another place.
Because a lot of these processes are automatic, Sierra users might not be aware of what the OS is doing on their behalf. If it sounds like a good idea to have macOS deciding what files to send to iCloud and what iTunes videos to remove, go for it.
For everyone else, we’d recommend turning off these tools or at least making sure you understand them fully before turning them on.
It can be challenging to check and analyze all contents of your disk space. Luckily, some tools can provide a disk scan and can save up lots of space on your Mac. Apps notarized by Apple is best for this job. CleanMyMac X, the app I talked earlier about, has a Large & Old Files feature, which finds and removes massive files stored on your Mac.
4. Change your scratch disk
If the disk being used is nearly full, change the directory for a more spacious one. Then, restart Photoshop. You can change the Scratch Disk location by pressing Command + Option when launching Photoshop. It can be a hassle but if you keep an eye on the available space on your scratch disk, you can do something when space is becoming limited. It’s also worth noting that problems don't just occur when the drive is completely full, hard drives should ideally never be above 85% capacity. Pass that threshold and problems will be just around the corner.
So, you've identified rapidly depleting free space on your Mac hard drive — now what? Well, it may be a good idea to change your scratch disk to another drive in your system (just 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 Mac OS X scratch disk purposes.
Follow these steps to change your scratch disk in Photoshop:
- Click on the Photoshop menu.
- Go to Preferences and then Scratch Disk.
- Tick the checkbox to select or remove a drive as the scratch disk.
- Click OK.
- Restart Photoshop.
You can change the Scratch Disk location by pressing Command + Option when launching Photoshop
5. Consider buying a new SSD
The scratch disk problem happens because of 2 simple reasons: lack of RAM, and lack of HDD space. Both can be addressed if you buy a Thunderbolt SSD (solid-state drive) to use as your Scratch Disk. By today’s standards, 60 GBs should be enough.
Buy an external SSD to use as a Scratch Disk. 60 GB should be enough.
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 HDD 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.
Loud fans noise is a sign your CPU is overloaded and approaching its carrying capacity.
7. Free up RAM in Terminal
When Photoshop gets paralyzed due to lack of RAM, there is a command you can run in Terminal.
- Open the Terminal app (find it in the Launchpad).
- Paste in:
- 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 out them too.
You can also download CleanMyMac (get free edition here) and use its Free UP RAM command.
- Install the app and click on Maintenance.
- 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. Search for hidden files in your Photoshop folder
Some projects’ leftovers are invisible and yet take up lots of space. There is a shortcut combination to display hidden files in whatever folder you are. So, open your main Photoshop folder and click Command + Shift + Period. Formatting usb stick for mac. If you find any greyed out folders, check their weight.
To see hidden files in any folder, press Command+Shift+Period.
As you see, there are many methods to solve “the scratch disks are full” error. There is also one more way to reorganize data on your Mac and save up some space. Disk defragmentation gathers related items and lets you delete unneeded data as well as leftovers. Note that the latest macOS doesn’t need to be defragmented as Apple has provided it with in-built utilities, which remove fragmented files automatically. So, defragmentation may only work for you if your Mac’s running the OS version earlier than OS X 10.2.
The 'Scratch Disk Is Full' error 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.
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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 does “scratch disks are full” error may appear?
The number one reason for “scratch disks are full” message is the lack of space in the drive where scratch disks are 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” issue?
One of the solutions is to change the scratch disk allocation. You may also need to clear Photoshop cache and remove temporary files.
These might also interest you:
What is taking up space on my Mac?
There comes a time in every computer's life when it is full of files and programs, slowing it down so much that its owner searches for an article such as this in order to cure it of these ailments (before it gets thrown out the window!).
Worry not, you're in the right place. This article will take you through 8 steps which will free up space on your Mac - removing unneeded files and clearing space for the stuff you actually need.
No matter if you're tech savvy or not, anyone can use these tips to breathe new life into their Mac.
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To find out how much space is available on your Mac:
- Open the Apple menu (the Apple icon in the top-left corner of your screen).
- Click 'About this Mac'.
- Click 'Storage'.
This overview will show what categories are taking up the most space, as well as how much space is available on your Mac.
The 8 sections below address the biggest culprits of space-hogging on your Mac and how to clean them up.
Jump straight to:
1. Mac OS Storage Management
The first port of call when making space on your Mac is to see what tools your Mac offers you for such a task.
If your Mac is running macOS Sierra or later, it has great built-in tools for managing files and optimizing storage. To access these tools, click the apple icon in the top-left corner of your screen > About this Mac > Storage > Manage…
As you can see this is also how to check storage on Mac. The tool shows a breakdown of the storage space taken up on your Mac by media such as Apps, Books, Photos and others.
Let's have a look at each tool to see how it can help:
- Store in iCloud: Quickly store files (Documents, Photos and Messages) from your Mac in iCloud. When considering how to clear space on Mac, getting rid of files quickly springs to mind- However, if you need to keep the files, you can just move them to an external hard drive, or into iCloud!
Enabling this option will allow your Mac to automatically save space when it’s needed.
This is great as you’ll be able to access your files on any device using your Apple ID. However, if you have a large number of files, you’ll need to purchase more storage space than your allotted free amount (5GB)- obviously, depending on the amount of space you need, this can quickly become an expensive option.
- Optimize Storage: For those who download and watch lots of movies and TV, this option can save you a lot of space and a lot of time. Enabling this option will allow your Mac to automatically remove such files (which can be HUGE depending on their length and quality) once you have watched them.
Empty Trash Automatically: Similar to the above, enabling this option allows the automatic removal of files, saving you time and space without having to keep on top of it manually. This will remove items in your Trash after 30 days of them being there. Be aware that once files have been removed from your Trash, you will not be able to retrieve them.
Side note: Many points in this article will advise the removal of unwanted files from your Mac. However, these files are not completely removed from your computer until you empty the Trash (the space is not regained until they are removed from Trash). You can manually empty it by clicking the Trash Can icon in your dock, then clicking 'Empty'.
Reduce Clutter: Find large and unused files on your Mac and delete them from your system. You’ll need to delete them manually, but it’s well worth it if you can remove files that you do not use.
Navigate to files that you don't need using the 'Large Files' or 'Downloads' sorters, then hit 'Delete..'. Note that this action will bypass sending the item to Trash, so it's permanent.
If you're finding unwanted files using the 'File Browser' tab, you'll need to right-click > 'Move To Trash'.
2. Find Duplicate Files Mac
The quickest way to free up space on your Mac is to automatically remove files that you don’t need. Without realizing it, you can accumulate gigabytes worth of duplicate files and folders on your computer.
The problem is that it can take so much time to find and delete these duplicates that people do not bother to do it even if they want to.
Luckily, you can use an app like Duplicate Sweeper to do this for you.
Duplicate Sweeper: Easily scan your Mac for duplicate files and photos. You can then select and remove duplicates based on your preferences. In this way you can keep your newest version of files and remove all duplicates with a click of a button.
In the example below, I was able to remove over 6000 files with one-click. This freed up 2.3 GB of space on my MacBook. Imagine manually going through and comparing 6000 files without Duplicate Sweeper.. it would have taken forever!
For more information about Duplicate Sweeper, or to download the free trial:Duplicate Sweeper homepage
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3. Unused Apps- Uninstall Programs on Mac
One of the biggest areas you should consider when looking at how to free up space on Mac is your Apps. Maybe unsurprisingly, apps on your Mac can be some of the largest files on your computer. Removing apps that you don’t use can free up a huge amount of space. Let’s list your apps by their files size:
Open Finder, then open the Applications section. Display the items as a list (using the button with 4 horizontal lines), then click the ‘Size’ header to reorder your applications by size. You can then work down the list and decide which applications you don’t use. Simply drag an application from the list into the Trash Can on your Dock to remove them.
Remember that you’ll need to empty your Trash Can to completely remove the applications from your Mac.
4. Clean up media and downloads
The quality of media like photo and video is constantly improving. Unfortunately, this usually means that the corresponding files are bigger than they used to be.
For this reason, your saved media could be a great place to free up some of that precious storage on your Mac.
Open Finder and look through your Pictures, Movies and Music folders. If there is media there that you don't want, select it and move it to Trash to get rid of later. If you prefer to delete this media from the associated apps like Photos and iMovie, see how to empty their trash.
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It is also recommended to check your Downloads file for unwanted files too.
This folder can receive copious amounts of files downloaded from multiple sources. Many of these files you may have only needed to read or use once.
You can get to your Downloads folder by opening a Finder window and clicking the 'Downloads' header.
Again, select whatever files you don't need, then right-click > Move to Trash/Bin.
Extra: Zipped / Archived files
If you receive a zipped file (with the .zip extension), opening it will unzip the file or folder and create the files in a non-zipped form.
This will create files that you can use, but it will not remove the (now unneeded) zip file. If you've already unzipped, you can delete the .zip file.
On the flip side, you can use file archiving to compress files or folders that you don't use regularly.
Say you have a folder of documents that you only need to save for safekeeping; right-click the folder in Finder and click 'Compress [file/folder name]'. This will compress the files and create a .zip file.
Don't forget to delete the original, uncompressed folder in order to save the space!
5. Delete iTunes backups
Depending on the number of files, photos, messages etc that you have stored on your iPhone, iPod or iPad, it’s backup on your Mac can be huge.
Keeping backups of your devices is a good idea. If something was to happen to your device, your data can be restored to it (or another device) using your backup. However, these backup files can be massive, and you may never need them! For this reason, consider backing up your devices to iCloud instead – freeing up space on your Mac.
To set your device to backup to iCloud, go to Settings > (your name) > iCloud > iCloud Backup.
To initiate a backup, connect your device to a power source and also to a Wi-Fi network. Lastly, ensure that your device screen is locked and that you have enough free space in iCloud to store the backup.
How to delete backups on Mac - You can also delete the backups which you already have stored on your Mac. To do this, open iTunes and go to iTunes > Preferences > Devices. If you don’t need the backups in the list, select and delete them!
Find out: where are iTunes backups stored?
Alternatively, if you don’t want to use iCloud for backing up your data, or if you only need certain data from your backups, you could use iBackup Extractor. This handy tool allows you to access and browse your backups, and extract any important photos, messages etc. that you need. You can save this data to your computer, then delete the backup from iTunes as seen above!
6. How to Delete Temporary Files on Mac
Some of the most common questions asked are 'how to clear cache on mac' and 'how to delete cookies on mac'. Well, let's answer those for you!
Temporary and cache are files that are stored locally in order to speed up processes. For example, images from a website that you visited can be cached, so that when you visit the page again, you don’t have to wait to download the images again, they are simply pulled in from the cache. That’s great for processes that you use regularly, but without care, your temporary and cached files can build up and eat away at your Mac’s performance.
Let’s see how to clear cache on mac – Open Finder > Go > hold ‘option’ and click ‘Library’ > Caches. Select and delete any cache files and folders that you don’t need to save space!
7. Taking out the Trash
Deleting files on your Mac usually only moves them to your Trash Can (or Bin).
This is great, because if you 'delete' something by accident, you can restore it to its original location - no harm done.
However, if you are culling files on your Mac to make space, you may wonder why you are not gaining storage after clicking delete.
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To permanently delete files from the Mac, you'll need to empty your Trash Can. To do this, simply click the Trash Can (or Bin) icon in your Dock.
Here, you can review or restore files in your Trash/Bin.
To permanently delete all the files in your bin, click Empty. You'll be asked if you're sure, and to confirm the permanent deletion of the files.
Deleting files from Photos, iMovie and Mail apps..
Generally, you'll be able to use the steps above to permanently delete files. However, some apps have their own way to manage 'deleted' files.
As such, you'll need to empty trash cans in individual apps to ensure that files are fully deleted.
An example of this can be seen in the Photos app:
How To Free Up Disk Space Mac
Click the 'Recently Deleted' header to access the trash in the Photos app.
After 'deleting' photos from the app, the files can remain in this section for up to 40 days before being automatically deleted.
If you are sure you'd like to permanently delete these photos, click 'Delete All' to remove them from your hard drive.
You can use similar steps to empty trash for other apps like iMovie and Mail.
8. Move files into external storage
The majority of the methods above cover how to delete unwanted files to gain space. But what you if want to keep your files?
If you need more space on your Mac, but deleting your files is not an option, you may want to consider investing in external storage.
You can purchase external storage drives pretty cheap nowadays.
The way this works is that you connect your external drive with your Mac via USB cable. The drive then pops up as a Location on your Mac:
You can then drag files from your Mac onto your external drive, or cut/paste them into specific folders on your drive.
These are the most effective steps to make the most of the available space on your Mac in our experience.
There's a lot of information above, but this is not an exhaustive list of everything you can do to clear space on your Mac. We hope that you now have the tools that you need to breathe new life into your Mac or MacBook.
Happy spring cleaning!