Part of: System Data on Mac: what is inside and how to reduce it safely (System Data)
Time Machine local snapshots are short-term copies of how your disk looked at a point in time. They live on your startup disk, they use some space, and macOS removes them on its own when it needs room. Most of the time the right action is to do nothing.
Snapshots are not backups
This is the part that confuses people. A backup is a copy of your files on another disk. A local snapshot is a record on the same disk of what changed, which lets Time Machine restore earlier versions even when the backup disk is not plugged in.
Because it sits on the same disk, a snapshot does not protect you if the disk fails. It is a convenience, not a safety net.
Why they take space
A snapshot only keeps data that changed after it was taken. If you delete a large file after a snapshot, the snapshot still holds that file’s data, so the space does not come back yet. That is one more reason the number can stay the same after you empty the Trash. The Trash guide covers the rest.
macOS treats this space as purgeable and removes old snapshots when a download, an update or an app needs room. Read more in the purgeable space guide.
How to list them
In Terminal, run:
tmutil listlocalsnapshots /Each line is one snapshot on the startup volume. On a Mac without any Time Machine snapshots, the list showed only entries starting with com.apple.os.update-. Those belong to macOS updates and are managed by the system.
To see the dates, you can also run:
tmutil listlocalsnapshotdatesTo see the options Time Machine’s command offers for removing snapshots, run tmutil help and read the entries for local snapshots. We list them here without running the removal on purpose: removing a snapshot cannot be undone, and in most cases there is no need.
When to act
Acting is only worth it when all of these are true:
- you checked the Trash is empty,
- the list shows Time Machine snapshots,
- you still need the space right now,
- and you do not need to restore from those snapshots.
In any other case, leave them, or wait a day. macOS releases them when it needs space. Turning Time Machine off, or backing up to the backup disk, also changes what is kept, but check Apple’s own instructions for your macOS version before relying on that.
Safe, Risky, Never
Safe
- Listing snapshots with
tmutil listlocalsnapshots /. - Leaving them to macOS.
Risky
- Removing Time Machine snapshots yourself. You lose those restore points.
- Removing them just to see the free-space number rise. It will rise, but macOS would have done it anyway.
Never
- Removing
com.apple.os.update-entries or touching system folders by hand. - Treating a snapshot as your only backup.
What breaks
If you remove a snapshot, your current files are not touched. What you lose is the chance to restore an older version from that moment. If that disk was your only copy of something, the real fix is a proper backup on another disk.
How long snapshots stay
Time Machine can create local snapshots regularly while backups are turned on. macOS keeps them for a limited time and removes older ones, and it removes them sooner when space gets tight. We do not state exact intervals here, because Apple can change them between versions. The takeaway is that snapshots are temporary by design.
On a Mac that has never had Time Machine set up, you may still see snapshots whose names start with com.apple.os.update-. Those are created by macOS updates and have nothing to do with your backups.
If your backup disk is not connected
Snapshots are what let you restore an earlier version of a file even when the backup disk is away. If you travel with a laptop, that is useful. It is also why they can grow: while the backup disk is not connected, local snapshots carry more of the history.
Connecting the backup disk and letting a backup finish is the normal way to bring things back to a steady state. Check the Time Machine settings in System Settings to see when the last backup ran.
Why a Time Machine tip may mislead you
Some guides treat “backups” and “snapshots” as one thing and tell you to delete your backups to free disk space. Backups sit on another disk and do not use the space of your startup disk at all. Deleting them would not free a byte there, and it would remove your safety net. Snapshots are the part on your startup disk.
A calm checklist
- Run
tmutil listlocalsnapshots /and read the list. - If you see only
com.apple.os.update-entries, stop. They are not Time Machine. - If you see Time Machine snapshots, check the date of your last backup.
- If you still need space, look first at the Trash and your largest folders. See the System Data guide.
- Only then consider removing snapshots, and read the options in
tmutil helpfirst.
Check what else is large
DiskJoy is our product. Its scan is read-only today: it shows reclaimable space by category and removes nothing. To see what else is large beside snapshots, run the scan.
Frequently asked questions
Do Time Machine local snapshots take up space?
Yes, they use space on your startup disk, but only for data that has changed. macOS counts them as purgeable and releases them when it needs the room.
Are local snapshots the same as backups?
No. A backup is a copy on another disk. A local snapshot lives on the same disk as your files, so it does not protect you if that disk fails.
How do I list Time Machine local snapshots?
Open Terminal and run tmutil listlocalsnapshots / to list snapshots on the startup volume.
Is it safe to delete local snapshots?
It is safe in the sense that your files are not removed, but you lose the ability to restore from those snapshots. Most people can leave them to macOS.