APFS snapshots on a Mac: what makes them and what they cost in space

APFS snapshots on a Mac are read-only copies of a whole volume, frozen at one moment and kept on the same disk. Time Machine makes most of them, about once an hour, when it backs up automatically. macOS makes others when it installs an update, and backup apps make their own.

A new snapshot costs almost nothing. It holds space only as the volume changes: every file you delete or overwrite after the snapshot was taken stays on the disk, in the snapshot, until the snapshot goes. That's why space can stay in use after you empty the Trash.

You can see them, and delete most of them, in Disk Utility: choose View › Show APFS Snapshots and select a volume. Time Machine's own snapshots go by themselves after 24 hours, or sooner when space is needed, so most of the time the right move is to leave them.

This post explains what makes each kind of snapshot, how they hold space, how to read Disk Utility's list, and which ones you can remove. If you only want the quick steps for Time Machine, the guide to Time Machine local snapshots has them.

APFS snapshots on a Mac at a glance

Most Macs carry two or three kinds of snapshot at once, made by different owners for different reasons. Here's who makes each one, where it lives and how it goes away.

Snapshot	Made by	Where it lives	How long it stays
Hourly local snapshots	Time Machine	The startup disk's data volume	About 24 hours
Last-backup snapshot	Time Machine	The startup disk's data volume	Until the space is needed
Pre-update snapshot	macOS	The startup disk	Removed by macOS
Sealed system snapshot	macOS	The system volume, Macintosh HD	Until an update replaces it
Backup app snapshots	Apps such as Carbon Copy Cloner	Volumes you turn them on for	The app's own retention settings
Backups on an APFS backup disk	Time Machine	The backup disk, not your Mac	Hourly, daily and weekly, until the disk fills

The first four use your Mac's own disk and need nothing from you beyond turning on Time Machine. Backup app snapshots appear only if you use such an app, and backups on a backup disk use that disk's space, not your Mac's.

What is an APFS snapshot?

Apple's Disk Utility guide describes a snapshot as a read-only copy of its parent volume, taken at a particular moment. A volume can have none, one or many of them.

"Read-only" matters. Nothing can change a snapshot once it's made, not even you. You can restore files from a Time Machine snapshot, and rename or delete a snapshot in Disk Utility, but you can't edit what's inside.

Which Macs have them?

Every Mac whose startup disk uses the Apple File System, APFS. That includes every Mac that runs macOS 26 Tahoe or macOS 27 Golden Gate.

Disks formatted as Mac OS Extended can't hold snapshots. Neither can exFAT drives, so a USB stick never fills with them.

How a snapshot holds space

To understand what snapshots cost, it helps to know how APFS writes files. The short version: it never overwrites data in place while a snapshot still needs the old copy.

Why is making a snapshot so quick?

APFS uses copy-on-write. When a file changes, the new data goes to new blocks on the disk, and the file system updates its records to point there. The old blocks are only freed when nothing points to them any more.

A snapshot is a saved copy of those records, the file system's metadata, at one moment. Making it copies no file data at all, so it takes a moment and a sliver of space. Howard Oakley, who writes about macOS internals at Eclectic Light, describes a new snapshot as very small for exactly this reason.

Why does a snapshot grow?

Because the old blocks now have something pointing to them: the snapshot. Delete a file after a snapshot was taken, and its data stays on the disk. Edit a file, and both the old and new versions take space.

Oakley gives a simple example. Take a snapshot, then delete a 1 GB file and change 2 GB of documents. The snapshot now holds about 3 GB that the live volume no longer uses. Nothing was copied; the snapshot simply kept the blocks from being freed.

Does a snapshot cover the whole volume?

Yes. APFS snapshots always take in a whole volume. There's no way to snapshot one folder, or to leave one folder out.

That has a consequence people rarely expect. Time Machine's Exclude from Backups list keeps items off your backup disk, but it doesn't keep them out of local snapshots. Oakley points out that a snapshot is of a whole volume, so excluded folders still hold space in it when their files change.

What's left out of snapshots?

Files that live on other volumes. macOS keeps swap files on a separate VM volume, so the memory macOS moves to the disk doesn't end up in your snapshots. Oakley notes that otherwise every snapshot would carry large swap files.

The system volume is separate too. Time Machine's hourly snapshots cover the data volume, Macintosh HD – Data, where your files, apps and settings live.

Snapshots and clones are different things

An APFS clone is a copy of a file that shares its blocks with the original until one of them changes. A snapshot shares blocks with the whole live volume. Both mean that deleting one copy can free less space than its size suggests.

The difference is who controls them. Clones are ordinary files you can see in Finder. Snapshots appear in no folder, and only Disk Utility, Time Machine and backup apps show them. The post on finding duplicate files explains why deleting a clone frees almost nothing.

What makes APFS snapshots on your Mac

Apple restricts which apps can make snapshots: they need a special permission from Apple. On a typical Mac, that leaves a short list of makers.

Time Machine's local snapshots

When Back Up Automatically is on, Apple says Time Machine saves a snapshot of your startup disk about every hour and keeps each one for 24 hours. It also keeps a snapshot of your last successful backup until space is needed.

These are local snapshots. They let you restore a file from an hour ago even when your backup disk is at home and you aren't. Apple also says Time Machine stores them only on disks that have plenty of free space.

Time Machine makes them only when it's set up. If you never added a backup disk, you won't have hourly snapshots, which is the case on many Macs.

The snapshot before a macOS update

Apple's article on local snapshots says that in macOS High Sierra 10.13 or later, another snapshot is saved before any macOS update is installed. It's a record of your disk from just before the update.

Apple doesn't say how long that snapshot stays. Like Time Machine's, it holds space for files that change after it was taken, and an update changes a lot. That's one reason free space can look low for a while after updating.

The sealed system snapshot

Since macOS Catalina, macOS runs from a separate, read-only system volume called Macintosh HD. macOS Big Sur went further with the signed system volume: a cryptographic seal over every byte of the system.

Apple's security guide says the signed system volume uses APFS snapshots, so if an update can't be completed, the old system version can be restored without reinstalling. In Oakley's account, the installer makes a snapshot of the system volume, seals it, and your Mac starts up from that sealed snapshot.

These snapshots sit on the system volume, with names that begin with com.apple.os.update. On one Mac running macOS 27, checked for this post, the system volume held three of them, and macOS marked none of them as purgeable.

Backup and cloning apps

Apps such as Carbon Copy Cloner can keep their own snapshots, each with its own schedule. Carbon Copy Cloner's documentation says it doesn't turn on snapshots for the startup disk by itself. You have to choose that.

It does take a snapshot of the source when a backup runs, and backs up from that frozen copy. If snapshots aren't turned on for that volume, it removes the snapshot when the backup ends.

Its documentation says it never deletes snapshots that other apps made. Oakley notes that it works the other way too: Time Machine doesn't manage Carbon Copy Cloner's snapshots.

Snapshots on your backup disk

Since macOS Big Sur, Time Machine can back up to an APFS disk, and each backup there is itself a snapshot. Apple says Time Machine keeps hourly backups for the past 24 hours, daily backups for the past month and weekly backups for all previous months, and deletes the oldest when the backup disk is full.

Those take space on the backup disk, not on your Mac, and Time Machine manages them by itself. The post on deleting backups from the backup disk covers the rare times you'd step in.

Can you make a snapshot yourself?

Not from any app macOS includes, other than by letting Time Machine run. Backup apps with Apple's permission can make them for you, on the schedule you set. Disk Utility can show, rename and delete snapshots, but it can't create them.

What APFS snapshots cost in space

There's no simple answer to "how big is this snapshot?", because snapshots share almost everything with each other and with the live volume. What a snapshot costs depends on what changed after it was taken.

What decides how much space a snapshot holds?

Three things. How much you delete or change after it's made. How long it's kept. And how many other snapshots share the same old blocks.

A Mac used for mail and browsing changes little in a day, so its snapshots stay small. A Mac that edits video, runs a virtual machine or builds large projects can change many gigabytes in an hour, and each hourly snapshot holds on to the old versions.

Which files make snapshots grow fastest?

• Large files that change in place, such as virtual machine disks, Docker's disk image and databases. Every change to them leaves old blocks behind in the snapshot.
• Temporary files and caches that apps write and delete in bulk. Oakley names apps that create lots of large temporary files as the main suspects.
• Big deletions. Clearing out 50 GB of old video doesn't free 50 GB while snapshots from before the deletion are still on the disk.
• Downloads you delete soon after. A large installer downloaded, used and deleted within the hour may still sit in that hour's snapshot.

How long does each kind of snapshot stay?

Retention is the other half of the cost: the longer a snapshot stays, the more change it collects. These are the documented defaults.

• Time Machine hourly snapshots1 days
• CCC hourly snapshots1 days
• CCC daily snapshots, startup disk3 days
• CCC SafetyNet snapshots, startup disk3 days
• CCC SafetyNet snapshots, other disks7 days
• CCC daily snapshots, other disks30 days

Defaults from Apple's article on Time Machine local snapshots and Carbon Copy Cloner 6's documentation. CCC keeps snapshots on the startup disk only if you turn that on, and also removes the oldest when free space runs low.

Time Machine's last-backup snapshot and macOS's pre-update snapshot have no published retention. Apple says only that Time Machine removes its snapshots as they age or as space is needed.

A worked example

At 9:00 you start a day of video work. Time Machine takes its hourly snapshot. At 9:40 you export a 30 GB file, check it, and delete it at 10:30. The 10:00 snapshot was taken while the file existed, so its 30 GB stays in use.

You empty the Trash. Finder now counts that 30 GB as available, because Apple counts snapshot space as available. Storage settings shows a larger System Data. And around 10:00 the next day, when the snapshot ages out, the space is free in every sense.

Why does deleting one snapshot free so little?

Because most of what it holds is shared with its neighbours. Oakley's advice is to delete older snapshots first, and he warns that deleting a snapshot in the middle frees less space than you might expect.

He also says you won't know how much space you'll get back until you delete them. That's why careful tools measure the free space before and after, instead of trusting an estimate.

How to see APFS snapshots in Disk Utility

Disk Utility has had full support for snapshots since macOS Monterey, and the steps are the same in macOS 26 Tahoe and macOS 27 Golden Gate. Looking is harmless: nothing changes until you click a button. The post on reading Disk Utility for storage covers its other views.

Show the snapshot list

1. Open Disk Utility, in the Utilities folder of your Applications folder.
2. Choose View › Show APFS Snapshots.
3. Select a volume in the sidebar. Its snapshots appear in a table at the bottom of the window.
4. When you're done, choose View › Hide APFS Snapshots.

For Time Machine's snapshots, select your startup disk's data volume, usually Macintosh HD – Data. If you don't see it, choose View › Show All Devices, as Oakley suggests, and look under your internal disk.

Which columns should you turn on?

Click the More pop-up menu, choose Show Columns, and select the ones you want. Apple lists XID, UUID, Date Created, Tidemark, Private Size, Cumulative Size and Kind. You can drag a column heading to move it.

Date Created and Private Size are the useful pair. Oakley describes Private Size as the data only that snapshot references, broadly what deleting it alone would free. Cumulative Size adds every older snapshot, so it's largest for the newest one and overstates what any single deletion frees.

What do the names mean?

Name in Disk Utility	Who made it	What to do
com.apple.TimeMachine. with a date and time	Time Machine	Leave it, or remove it if you need the space now
com.apple.os.update- and a long code	macOS's update process	Leave it to macOS
Starting with a backup app's name or identifier	That backup app	Change its settings in the app
An unfamiliar name	An app with Apple's snapshot permission	Find the app before you delete anything

A Time Machine name tells you when it was taken: the date, then the hour, minutes and seconds. Several in a row, about an hour apart, is normal.

Why is the list empty?

Usually because there's nothing to show. If Time Machine isn't set up, there are no hourly snapshots, and many Macs have none on the data volume. Check that you selected the data volume rather than the system volume or an external disk.

Deleting APFS snapshots

You have three ways to remove snapshots, and one rule above them: let each snapshot's owner remove it if you can. Removing snapshots never touches your current files, but it does remove a way back.

Remove one snapshot in Disk Utility

1. In Disk Utility, choose View › Show APFS Snapshots and select the volume.
2. Select one or more snapshots in the table.
3. Click Delete Snapshot, and confirm.

Start with the oldest. Oakley adds one piece of advice for Time Machine's snapshots: keep the most recent one, because without it the next backup could be a full backup of the whole data volume.

Have Time Machine remove its own

When you need the space now and don't want to pick snapshots one by one, Apple's method is to pause automatic backups.

1. Choose Apple menu › System Settings, click General, then click Time Machine.
2. Click Options, choose Manually from the Backup Frequency menu, and click Done.
3. Wait a few minutes while Time Machine deletes its local snapshots.
4. Set Backup Frequency back to what it was. Time Machine remembers its backup disks.

The steps are the same in macOS 26 Tahoe. In macOS Monterey and earlier, the setting was in System Preferences › Time Machine: deselect Back Up Automatically, or use the Off and On switch, then turn it back on.

Remove a backup app's snapshots in that app

Backup apps keep track of their own snapshots and thin them on their own schedule. The app shows them beside its retention settings, so it's the clearest place to remove them.

In Carbon Copy Cloner, reveal the sidebar and click the volume. The app lists its snapshots and the volume's retention policy, and you can select snapshots and press Delete. Shorten the retention policy there if its snapshots keep taking too much room.

Can you delete the com.apple.os.update snapshots?

Leave them alone. They're part of how macOS starts up and updates, and your Mac runs from one of them. Apple's security guide says that because the system volume uses snapshots, if an update can't be completed, the old system can be restored without reinstalling.

Instructions online that delete them with Terminal commands are ones to skip. If an update seems stuck, install it again through System Settings › General › Software Update, and let macOS manage its own snapshots.

Which removal method fits?

Method	What it removes	Best for
Wait	Time Machine removes its snapshots as they age or as space is needed	Most days
Time Machine settings	All of Time Machine's local snapshots	Making room for an update or a large copy
Disk Utility, one at a time	The snapshots you select	Removing old snapshots while keeping the newest
The backup app	That app's snapshots	Snapshots from Carbon Copy Cloner and similar apps

What do you lose when you delete a snapshot?

The ability to restore files from it. A file you deleted this morning that exists only in a local snapshot is gone for good once that snapshot is. Apple's article is clear that backups on your Time Machine disk aren't affected.

Deletion can't be undone, and it isn't instant. Oakley notes that deleting a snapshot is slower and less predictable than making one, because APFS has to find and free every block nothing else needs.

Snapshots and the numbers macOS shows

The most confusing thing about snapshots isn't the space they hold. It's that every part of macOS reports that space differently.

Is snapshot space purgeable?

Apple says your Mac counts the space used by snapshots as available storage. Its article goes further: you don't need to think about it, because snapshots don't use the space needed to download files, copy files or install software.

In practice, macOS has to remove snapshots to hand that space over, and it doesn't always do it in time. In tests on macOS Tahoe 26.6.2, Oakley saw a 12.89 GB copy to another volume fail while a snapshot held the space, and twice saw macOS not free a snapshot when he expected it to.

Where does each part of macOS count it?

Where you look	How snapshot space appears
Finder	Counted as available
Disk Utility's Info window	Shown as purgeable, apart from free space
Storage settings	Counted inside System Data
Disk Utility's snapshot list	Each snapshot, with its Private Size

So the same 30 GB can be "available" in Finder, "purgeable" in Disk Utility and "System Data" in System Settings › General › Storage, all at once. None of them is wrong; they answer different questions.

The post on removing purgeable space goes through those figures in detail, along with the other kinds of purgeable space, such as iCloud Drive downloads.

Why does System Data drop overnight?

Because hourly snapshots age out a day after they were taken. A large deletion yesterday, held by snapshots, becomes truly free space today. A restart can drop it further by clearing swap, which isn't in snapshots but is in System Data.

Why did a macOS update make space disappear?

Snapshots are part of it. macOS saves a snapshot before installing the update, which holds on to everything the update and the following hours change. The update also builds a new sealed snapshot of the system, and Storage settings needs time to work its figures out again.

Give it a day or two. If free space doesn't come back, check Disk Utility's list for Time Machine snapshots and for apps you forgot were making them. Snapshots aren't the only cause: the post on storage filling up after a macOS update covers the others.

When snapshots become a problem

Most Macs never need any of this. Snapshots become a problem in a few predictable situations, and each has a fix that doesn't involve deleting them over and over.

A large update or copy says there isn't room

Free space is short, and macOS hasn't freed snapshot space quickly enough. Remove Time Machine's local snapshots with the Backup Frequency method, wait a few minutes, then try again. Turn automatic backups back on afterwards.

A backup disk you no longer use

If you stopped using a Time Machine disk but never removed it from Time Machine settings, Time Machine keeps trying to back up, and can keep making local snapshots. Remove the old disk in System Settings › General › Time Machine, or turn automatic backups off, so it stops.

Virtual machines, Docker and big databases

These keep large files that change all day, and every hourly snapshot holds the old blocks. Excluding them from backups doesn't help, since exclusions don't apply to snapshots. Oakley suggests keeping such files on a separate APFS volume that isn't backed up.

A second volume shares the same disk's free space, so it costs nothing to make. In Disk Utility, select your startup volume and click the add volume button in the toolbar. Then add the new volume to Time Machine's Exclude from Backups list.

A backup app keeping too many

If Disk Utility lists dozens of snapshots that aren't Time Machine's, a backup app is probably keeping them on the startup disk. Open that app and shorten its retention on the startup disk, or turn off snapshots for it there.

A snapshot that won't go away

Occasionally an old snapshot stays long after it should have aged out. Check its name first: com.apple.os.update snapshots belong to macOS and aren't yours to remove. For a Time Machine snapshot, try the Backup Frequency method, then a restart, then Disk Utility.

If Disk Utility can't delete a Time Machine snapshot, run First Aid on the volume, which checks the disk for errors. If that doesn't help, Apple Support can look at it with you.

How APFS snapshots changed across macOS versions

Snapshots arrived with APFS, and almost every version since has added a use for them or a place to see them. When you follow older advice, check which version it was written for.

macOS version	What changed for snapshots
High Sierra 10.13	APFS startup disks; Time Machine's local snapshots become APFS snapshots; a snapshot before each macOS update
Catalina 10.15	macOS moves to a separate read-only system volume, beside Macintosh HD – Data
Big Sur 11	The signed system volume runs from a sealed snapshot; Time Machine can back up to APFS disks
Monterey 12	Disk Utility gets full snapshot support: View › Show APFS Snapshots, sizes and Delete Snapshot
Ventura 13	Time Machine moves to System Settings, with Backup Frequency under Options
Tahoe 26 and Golden Gate 27	The same Time Machine and Disk Utility steps as Ventura

What does older advice get wrong?

Guides written before macOS Ventura tell you to open System Preferences and deselect Back Up Automatically. On macOS 26 and 27, the same thing is Backup Frequency › Manually in Time Machine's options.

Before Monterey, Disk Utility's support for snapshots was limited, so older guides send you to Terminal. Disk Utility now lists them with their dates and sizes, so you can look without typing anything.

Do external drives get snapshots?

Only if something makes them there. Carbon Copy Cloner's documentation says it turns snapshots on by itself for APFS volumes on external disks that you use as a backup source or destination.

Those snapshots use the external disk's space, not your Mac's. To see them, select the external volume in Disk Utility with Show APFS Snapshots turned on.

Mistakes to avoid with snapshots

Snapshots attract more bad advice than most parts of macOS, because the space they hold is hard to see and easy to blame.

Don't turn off Time Machine to save space

Time Machine's snapshots are a feature, not a leak. They're your quickest way back to a file you deleted an hour ago, and macOS removes them on its own. Turning off automatic backups for good to stop them also stops your backups.

Don't treat snapshots as a backup

A local snapshot lives on the same disk as your files. If the disk fails, or the Mac is lost, the snapshots go with it. Carbon Copy Cloner's documentation makes the same point: snapshots aren't a replacement for a backup on separate hardware.

Don't rename snapshots

Disk Utility lets you rename a snapshot, but Apple warns that renaming one may make it unsuitable for its intended purpose. There's nothing to gain from it: a new name frees no space.

Don't paste Terminal commands to clear them

Guides that hand you a command to "clear snapshots" or "free purgeable space" are best closed. Commands that delete things can't be undone, and fake cleanup guides are a known way to spread malware. Every step in this post goes through Disk Utility, System Settings or the app that made the snapshot.

Don't expect deletion to free space instantly

APFS frees a deleted snapshot's blocks in the background, and Storage settings works its figures out slowly. Wait a few minutes, then look at Disk Utility's Info window rather than Storage settings.

How the app does it

Wombit shows what's using your storage, explains every item in plain language, and clears it safely: Trash first, undoable and logged. File names and paths never leave your Mac.

Its space meter shows how much of the available space is purgeable and how many local snapshots there are, so you can see when snapshots hold space. System Data, explained puts local snapshots in their own bucket instead of hiding them in one number.

The Local Snapshots page lists every snapshot: when it was made, which app made it, and whether macOS removes it by itself. Snapshots come from this catalog entry:

• Time Machine local snapshots

  Hourly snapshots of your startup disk that Time Machine keeps on the disk itself, so you can restore files even without your backup disk.

  Managed by macOS · Runs tmutil for Time Machine's own snapshots, through the helper

Local snapshots are Managed by macOS: explained and handled through macOS's own mechanism, never moved to the Trash. When you choose, the app deletes only Time Machine's own snapshots, with Time Machine's own tool, or asks Time Machine to remove as many as it can.

Both need an administrator's name and password, through the helper. Because macOS doesn't say what a snapshot holds, the app measures the available space before and after, and shows the difference. Snapshots made by macOS updates and by other backup apps are listed and explained, and left to their owners.

Seeing your snapshots is free. Removing Time Machine snapshots is PRO: one payment of $4.99 with lifetime access. Every Pro tool's review is free to open, so you see what would go and why before you buy.