Time Machine local snapshots are quietly holding 30 GB

15 September 2026

If Time Machine is on and your backup disk isn't plugged in, which for a laptop is most of the time, macOS takes a snapshot of your startup disk every hour and keeps them for about a day, longer if no backup has happened. Each snapshot pins every file that existed at that moment. Delete a 20 GB file and nothing changes until the last snapshot that knew about it is gone.

Where they show up

Nowhere you can click. Storage settings counts them as "System Data"; Finder's Get Info counts them as purgeable. There is no folder to open. On one Mac they were holding 31 GB.

List them

tmutil listlocalsnapshots /

Each line is one snapshot, named by its date, like com.apple.TimeMachine.2026-09-15-201512.local.

Delete them

tmutil deletelocalsnapshots 2026-09-15-201512   # one, by its date
tmutil deletelocalsnapshots /                   # every snapshot on the startup disk

Or ask macOS to thin them until it has freed a given number of bytes (here 30 GB, at the highest urgency):

tmutil thinlocalsnapshots / 30000000000 4

If macOS refuses, prefix the command with sudo.

What you lose

The ability to restore a file to how it was earlier today from the local copy. Your real backups on the Time Machine disk are untouched, and macOS takes a fresh snapshot within the hour. It is supposed to delete these itself when space runs low, and it often doesn't do it in time, which is why "I deleted everything and nothing changed" is such a common story.

Other snapshot makers

Carbon Copy Cloner and macOS updates create snapshots too. They appear in the same list and delete the same way.

In ddeploy

System Data → Time Machine snapshots: count, size, one Purge button.

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