Backing Up a MacBook: Time Machine's Local Snapshots, and Why Laptops Are the Hard Case

By Tom Langston · 21 July 2026

macOS
Backup
Time Machine
Apple

TL;DR

Backing up a laptop is genuinely one of the hardest problems in computing. A MacBook is rarely sitting next to its Time Machine drive, yet it is far more likely than a desktop to be dropped, overheated, misplaced, or stolen. Time Machine quietly bridges that gap with local snapshots, saved to your Mac’s own startup drive while you are away from your backup disk. They are a real safety net for recovering a file you just corrupted or deleted, but they are not a true backup: if the drive itself fails or the laptop vanishes, the snapshots go with it.

With Time Machine turned on and no backup drive connected, macOS automatically saves local snapshots to your startup drive (roughly one a day after startup, plus a weekly one).
They store changed files, so you can restore a recent version even with nothing plugged in. In the Time Machine app, snapshots you can restore from show a bright red tick.
They are not a backup. If the drive dies or the laptop is lost or stolen, the snapshots are lost with it.
They self-manage: kept until your drive drops below 20% free, then the oldest are trimmed, and trimmed aggressively below 10% (or under 5 GB).
This is the macOS face of a bigger rule covered in the system rollback guide: a snapshot on the same device is not a backup.

Now for the more technical explanation

Why laptops are the hard case

Time Machine is wonderful for an immobile Mac with plenty of fast external storage always attached. A laptop is the opposite. If your MacBook seldom has its backup drive to hand, it will inevitably go long stretches between proper backups, exactly when you can least afford to.

And laptops are the machines most likely to fail or lose data. They run hotter, which ages their components faster. They take physical and mechanical knocks. And they are all too easily stolen or left behind. If you always had a fat internet connection, iCloud or another cloud backup could be ideal, if relatively costly, but most mobile users rarely have that luxury when it counts.

What local snapshots actually are

Local snapshots are Time Machine’s stopgap for exactly this situation. With Time Machine turned on (in its pane in System Settings, or System Preferences on older macOS), and while you are away from your normal Time Machine drive, macOS automatically writes a local snapshot to your startup drive: one roughly every 24 hours after you start up, plus an additional snapshot each week.

Crucially, these are not full backups. They store only the files that have changed, which is what makes them cheap enough to keep on the same drive you are working from.

Restoring from one

You recover from a local snapshot the same way you always use Time Machine: open the Time Machine app. When you are away from your backup drive, the snapshots you can restore from are marked with a bright red tick. Backups that live only on your full backup drive are shown with dimmed ticks, and their contents appear blank.

So if the current copy of a working document becomes corrupted or is lost, you can step back to a recent version even with no backup disk connected. That is the whole point.

How they manage disk space

Because they sit on your startup drive, local snapshots have to be self-limiting:

Time Machine keeps making them until only 20% of your startup drive is free. It then starts removing the oldest snapshots to reclaim space, exactly as it would thin a full backup.
Removal becomes more aggressive at 10% free or less (or under 5 GB). At that point it may keep only the latest snapshot, and stop creating new ones.

Where to see them

Local snapshots do not appear in Finder’s usual storage figures, which is why the space they occupy can be a surprise. On current macOS you can see them in System Settings → General → Storage (older macOS showed the same under About This Mac → Storage). Apple’s standard colour scheme shows all backups in purple: purple usage on your startup drive is your local snapshots.

The catch, and managing them

Local snapshots are a mixed blessing. If your drive suffers any significant failure, or the laptop is lost altogether, so are the snapshots. They are better than nothing, but on a small SSD you may want to keep them in check.

Here is where current macOS differs sharply from the older advice you will still find online. Since Time Machine moved to APFS snapshots (from macOS High Sierra onward), the old Terminal toggle, sudo tmutil disablelocal and enablelocal, no longer exists, and there is no command that disables local snapshots on their own.

Apple’s supported way to stop them is in Time Machine’s settings, by turning off the automatic backup schedule (which is what creates the local snapshots in the first place):

macOS Ventura and later: open Time Machine settings, click Options, set Backup Frequency to Manually, and click Done.
macOS Monterey and earlier: deselect Back Up Automatically (or use the On/Off switch).

Give it a few minutes and macOS clears the existing local snapshots. Your backup destination stays configured, so you can still run a backup by hand: you have only switched off the automatic schedule that was also making the snapshots. The trade-off is the obvious one, with automatic snapshots off you lose the drive-disconnected, on-device rollback.

What you can do from Terminal with tmutil on current macOS:

Create one now: tmutil localsnapshot (no sudo needed).
List them for your startup volume: tmutil listlocalsnapshots / (or tmutil listlocalsnapshotdates for just the dates).
Delete a specific snapshot: sudo tmutil deletelocalsnapshots <snapshot-date>, using a date from the list above.
Thin them to reclaim space: tmutil thinlocalsnapshots / <bytes-to-free> <urgency>, which asks macOS to purge older snapshots down to the free space you specify.

You will still see the older tmutil snapshot, tmutil listbackups, and tmutil machinedirectory in many guides, but those belong to the pre-APFS world, or refer to the destination backup drive rather than today’s on-disk local snapshots, so prefer the commands above on a modern Mac.

The versions alternative

Recent macOS, and compatible apps, also keep versions of documents you are actively working on. One efficient way to use limited laptop storage is to turn Time Machine’s local snapshots off and lean on saved versions instead, which are captured more frequently, hourly or more often. The trade-off: with local snapshots off, you cannot restore from a proper backup at all until you return and reconnect to your full Time Machine drive.

The bottom line

As at the start: backing up laptops remains one of the trickiest problems in computing. Local snapshots are a genuine, automatic safety net for the file you just broke, but they are not a substitute for a real, off-device backup. Treat them as the belt while a proper Time Machine drive, and ideally an off-site copy, is the braces. If your laptop can be stolen, pair this with full-disk encryption so a thief gets the hardware but not your data.

Written by Tom Langston, IT Infrastructure and Cybersecurity.