About Time Machine local snapshots

Local snapshots help Time Machine restore data even when your Time Machine backup disk isn't available. 

Your Time Machine backup disk might not always be available, so Time Machine also stores some of its backups to your built-in startup drive and other local drives. These backups are called local snapshots.

  • A daily snapshot is saved every 24 hours, beginning from the time you start or restart your computer.
  • A weekly snapshot is saved every week.
  • Starting with macOS High Sierra, an additional snapsnot is saved before installing any macOS update.

How to use local snapshots

When you enter Time Machine, a timeline appears on the right side of the screen. Each dated tick mark in the timeline is a backup, and each backup has a color when you move the pointer over it.

macOS High Sierra, Sierra, El Capitan, or Yosemite:

  • A bright red tick mark is a backup that can be restored now, either from a local snapshot or your backup drive. When your backup drive isn't available, only the local snapshots are bright red.
  • A dimmed red tick mark is a backup that can be restored from your backup drive after that drive becomes available. Until then, the stack of windows on the screen shows a blank window for that backup.

OS X Mavericks or earlier:

  • A gray tick mark is a backup that can be restored now from a local snapshot.
  • A bright pink tick mark is a backup that can be restored now from your backup drive. 
  • A dimmed pink tick mark is a backup that can be restored from your backup drive after that drive becomes available. Until then, the stack of windows on the screen shows a blank window for that backup.

Time Machine window

How local snapshots use storage space

Time Machine in macOS High Sierra stores snapshots on every APFS-formatted, all-flash storage device in your Mac or directly connected to your Mac. Time Machine in earlier macOS versions stores snapshots only on the internal startup disk of Mac notebook computers. 

To make sure that you have storage space when you need it, snapshots are stored only on disks that have plenty of free space. When storage space gets low, snapshots are automatically deleted, starting with the oldest. That's why Finder and Get Info windows don't include local snapshots in their calculations of the storage space available on a disk.

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