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What is a scratch disk?
A scratch disk is a hard disk drive or SSD used for temporary storage while Photoshop is running. Photoshop uses this space to store portions of your documents and their history panel states that don’t fit in the memory or RAM of your machine.
By default, Photoshop uses the hard drive on which the operating system is installed as the primary scratch disk.
How to set your scratch disk preferences
If Photoshop 2019, or earlier, cannot launch because the scratch disk is full, hold down the Cmd + Option keys (macOS) or Ctrl + Alt keys (Windows) during launch to set a new scratch disk.
You can tweak scratch disk settings in the Preferences > Scratch Disks section.
- Choose Edit > Preferences > Scratch Disks (Windows) or Photoshop > Preferences > Scratch Disks (Mac).
- In the Preferences dialog, select or deselect the active check box to enable or disable a scratch disk. To change the scratch disk order, click the arrow buttons.
- Click OK. To apply the changes, restart Photoshop.
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How much scratch disk space do you need?
Minimum free space on a scratch disk should be 6 GB for Photoshop desktop. However, this is the minimum space that Photoshop tries to keep free in the scratch disk, and the available space that Photoshop considers in a scratch disk is the 6 GB subtracted from the current free space in the disk. So, if the free space in your scratch disk is 10 GB, available space that Photoshop will consider in the scratch disk is 10 – 6 = 4 GB, which may/may not be enough for the current operation being performed.
- If you make small changes only, you need a minimum of 10 GB scratch disk space for Photoshop (with default preferences, brushes, patterns, etc). It is recommended to have minimum 20 GB of free space on your OS hard drive while working with Photoshop. Additional free space may be required based on the file type you’re working with.
- If you make large changes to dense pixel layers (that is, using several filters on complex background images or many edits to large smart objects) you could need as many times the size of the original file as there are history states.
Supported drive formats for scratch disks
macOS: macOS extended
Windows: NTFS, exFAT, FAT32
Drives not recommended for scratch disk
- Network drives
- Thumb drives
- Any USB-2 drive
- NTFS formatted drives on macOS
Recommended settings for scratch disks
- For best performance, connect the scratch disks to a compatible port that has the highest bandwidth limit of all the available ports. The bandwidth limits for various ports are as follows:
Thunderbolt = 10GB/sec
eSATA = 600MB/sec
PCIe = 500MB/sec
USB3 = 400MB/sec - To improve performance, set the scratch disk to a defragmented hard disk that has plenty of unused space and fast read/write speeds. If you have more than one hard drive, you can specify additional scratch disks. Photoshop supports up to 64 exabytes of scratch disk space on up to four volumes. (An exabyte equals 1 billion GB.)
- If your startup disk is a hard disk, as opposed to a solid-state disk (SSD), try using a different hard disk for your primary scratch disk. An SSD, on the other hand, performs well as both the primary startup and scratch disk. In fact, using an SSD is probably better than using a separate hard disk as your primary scratch disk.
- Scratch disks should be on a different drive than any large files you are editing.
- Scratch disks should be on a different drive than the one your operating system uses for virtual memory.
- RAID disks/disk arrays are good choices for dedicated scratch disk volumes.
- Defragment drives with scratch disks regularly.
How to adjust scratch disk preferences?
Note:
If Photoshop 2019, or earlier, cannot launch because the scratch disk is full, hold down the Cmd + Option keys (macOS) or Ctrl + Alt keys (Windows) during launch to set a new scratch disk.
You can tweak scratch disk settings in the Preferences > Scratch Disks section.
- Choose Edit > Preferences > Scratch Disks (Windows) or Photoshop > Preferences > Scratch Disks (Mac).
- In the Preferences dialog, select or deselect the active check box to enable or disable a scratch disk. To change the scratch disk order, click the arrow buttons.
- Click OK. To apply the changes, restart Photoshop.
How much scratch disk space do you need?
The scratch space required depends on how you edit and the number of history states in memory.
- If you make small changes only, you need a minimum of 1.5 GB scratch disk space for Photoshop (with default preferences, brushes, patterns, etc.) plus two times the size of all the files you have open at the same time.
- If you make large changes to dense pixel layers (that is, using several filters on complex background images or many edits to large smart objects) you could need as many times the size of the original file as there are history states.
Photoshop always reserves 6 GB of space on boot drives and 1 GB on non-boot drives to avoid causing problems for the operating system by running a drive completely out of space. Having hundreds of patterns or brushes loaded significantly increases the required scratch space for Photoshop to launch.
Recommended settings for scratch disks
- For best performance, connect the scratch disks to a compatible port that has the highest bandwidth limit of all the available ports. The bandwidth limits for various ports are as follows:
Thunderbolt = 10GB/sec
eSATA = 600MB/sec
PCIe = 500MB/sec
USB3 = 400MB/sec - To improve performance, set the scratch disk to a defragmented hard disk that has plenty of unused space and fast read/write speeds. If you have more than one hard drive, you can specify additional scratch disks. Photoshop supports up to 64 exabytes of scratch disk space on up to four volumes. (An exabyte equals 1 billion GB.)
- If your startup disk is a hard disk, as opposed to a solid-state disk (SSD), try using a different hard disk for your primary scratch disk. An SSD, on the other hand, performs well as both the primary startup and scratch disk. In fact, using an SSD is probably better than using a separate hard disk as your primary scratch disk.
- Scratch disks should be on a different drive than any large files you are editing.
- Scratch disks should be on a different drive than the one your operating system uses for virtual memory.
- RAID disks/disk arrays are good choices for dedicated scratch disk volumes.
- Defragment drives with scratch disks regularly.
Drives not recommended for scratch disk
- Network drives
- Thumb drives
- Any USB-2 drive
Troubleshoot ‘scratch disk full’ error
Free up additional disk space
‘Scratch disk full’ often means that the drive (or drives) used for scratch disks are running low or out of available space.
Free up additional hard drive space by deleting unnecessary files from the scratch disk, or by moving your files off the scratch disk to another storage location.
Specify appropriate drives for scratch disk
By default, only the OS drive is selected as Photoshop’s scratch disk. If you have more than one drive or partition, make sure to select the fastest drives with the most free space as your scratch disk(s). You can also resolve a ‘scratch disk full’ condition by selecting additional drives for use as scratch disks. See How to adjust scratch disk preferences?
Reset Photoshop preferences
On rare occasions when Photoshop or the system crashes, Photoshop’s preference file can get corrupted and this can affect Photoshop’s handling of scratch disks. Resetting Photoshop’s preferences and then reconfiguring the scratch disk preferences, can resolve ‘scratch disk full’ errors. See Reset Photoshop preferences.
Disable auto-recovery saving
By default, Photoshop attempts to auto-recover your document in case of an unexpected Photoshop exit such as a crash or computer reboot.
Disabling the Edit (Win) / Photoshop (Mac) > Preferences > File Handling > Automatically Save Recovery Information Every [N Minutes] reduces the size of Photoshop’s temporary file (scratch) at the risk of having no auto-recovery.