Mac: What is the large “sleepimage” file under /private/var/vm?

Today I tried the hard drive or SSD cleanup tool “GrandPerspective” and I noticed a file that was a few gigabytes in size. It has the name “sleepimage” and is located in the path /private/var/vm.

Everything about the “sleepimage” file on the Mac

  • The sleep image saves the contents of the main memory (RAM) before the Mac goes to sleep
  • When the Mac wakes up, it restores the state from the sleep image
  • There is no point in deleting the sleep image as it will be recreated the next time it hibernates
  • Instead, you should clean up other areas such as unnecessary files, the trash or unused apps to permanently free up storage space
This is where the sleepimage file is located, which saves the state of your Mac's RAM.
This is where the sleepimage file is located, which saves the state of your Mac's RAM.

What is the function of the sleepimage file?

The sleep image is a file that saves the contents of the main memory (RAM) before your Mac goes to sleep.

Hibernation is triggered when the MacBook's battery is almost empty or you start it manually. The entire contents of the volatile RAM are written to the “Sleepimage” file on the hard drive.

This allows the Mac to restore the saved state from the sleep image when it restarts. You can then continue exactly where you left off before the system went to sleep.

The sleep image serves as a backup of the RAM so that no data is lost if the battery runs out. When the system starts, macOS loads the image back into memory.

I discovered the file on my Mac using the GrandPerspective tool.
I discovered the file on my Mac using the GrandPerspective tool.

Why it is pointless to delete the file to save disk space

Some Mac users may delete the sleep image file to save space on the hard drive of their MacBook Pro, MacBook Air, or iMac. At first glance, this seems to make sense, as the file can be several gigabytes in size - depending on the size of your RAM.

However, all this effort is of little use because the Mac will simply recreate the file. The storage space is only released temporarily.

It makes more sense to tidy up other areas to permanently free up hard drive space on your MacBook or iMac. These include deleting files that are no longer needed, emptying the trash or uninstalling unused apps.

I can recommend two tools for this action:

  1. Grand Perspective – free, but not super comfortable
  2. Daisydisk – costs $20, but is fast, looks good and is pleasant to use

Both are useful for locating large files on your Mac and ultimately freeing up space on your MacBook Pro/Air or iMac.

Mac sleep FAQ

How do I tell if my Mac is sleeping or turned off?

When the Mac is in sleep mode, a small status LED often lights up or the Apple logo flashes slowly. If the Mac is turned off, no lights are on.

In what situations should I turn off my Mac instead of putting it to sleep?

You should turn off your Mac if you don't plan on using it for a long time, as this saves power and protects the hardware.

Can updates be installed while Mac is sleeping?

No, updates cannot be installed while in sleep mode as the Mac must be completely turned on.

How long does it take to “wake” a Mac from sleep?

Typically, it only takes a few seconds for a Mac to wake up from sleep, depending on the speed of the hard drive and the amount of RAM content stored.

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