Time Machine or a folder snapshot: which should you use to undo a change?
Both Time Machine and a folder snapshot can bring a folder back. They answer different questions, and picking the wrong one is how people end up with no undo at the moment they need it. This guide compares them on what actually decides it: which moment you can go back to, how long it takes, and what each one protects against. Checked on macOS 27.0.1; Apple’s behavior is from its own documentation, linked below.
The short answer
- You want protection against a lost disk, a stolen Mac or a deletion you notice next week: Time Machine.
- You are about to change a folder and want to undo exactly that change: a snapshot of that folder, taken right before.
- You care about both: use both. They don’t replace each other.
What Time Machine can go back to
Time Machine restores the moments it happened to back up. Apple says it makes hourly backups for the past 24 hours, daily backups for the past month and weekly backups for all previous months. So:
- A change you made 20 minutes ago has, at best, a copy from up to an hour earlier.
- Anything you created and changed inside the same hour may have no earlier version at all.
- After a day, the hourly copies thin out to daily ones.
Time Machine can also keep local snapshots on the Mac’s own disk. Apple’s page on local snapshots says they are made hourly, on APFS disks, and are removed when the Mac needs the space or when they’re older than 24 hours. They exist so you can recover earlier versions when the backup disk isn’t connected.
What Time Machine does well, and a snapshot can’t: the backup lives on another disk. If the Mac’s disk fails, the Mac is lost, or an update goes badly, the backup is still there.
Getting a fresh Time Machine copy before a risky change
If the backup disk is connected, click the Time Machine icon in the menu bar and choose Back Up Now. Apple documents this as the way to start a backup immediately. It backs up the whole Mac, so the time depends on how much has changed since the last one. Once it finishes, you have a restorable moment from right before your change.
To restore later, open the folder that contains the one you want, choose Browse Time Machine Backups from the same menu, pick the moment, select the folder and click Restore. The full steps and the Finder prompt you’ll see are in how to restore a folder to a previous version.
What a folder snapshot is
On APFS, a clone copies a folder without copying its data: both folders share the same blocks until a file changes. We measured this on macOS 27.0.1: a folder with 2,000 small files and a 300 MB file cloned in about 0.2 seconds and used about 1.3 MB of extra space. The how-to is in how to clone a folder on a Mac.
A snapshot made this way:
- records one folder, at the moment you choose,
- takes seconds, whatever the folder’s size, because the time depends mostly on the number of files,
- costs almost nothing until files change,
- lives on the same disk as the folder.
That last point is the catch. If the disk fails, the snapshot goes with it. And it’s only there if you remembered to take it before the change.
Side by side
| Time Machine | Folder snapshot | |
|---|---|---|
| Covers | Whole Mac | One folder |
| Which moments | The ones it backed up (hourly for 24 hours, per Apple) | The one you took, just before the change |
| Needs a disk | Yes, an external or network disk for full backups | No, same disk |
| Speed to create | Minutes if you use Back Up Now, depending on changes | Seconds |
| Extra space | On the backup disk | Almost none until files change |
| Survives a failed Mac disk | Yes | No |
| Restores one folder | Yes, by browsing the backup | Yes |
| Happens on its own | Yes | No, you take it (or an app does) |
Which one for which situation
| You are about to… | Better undo | Why |
|---|---|---|
| Let a script or an AI agent rewrite a project folder | Folder snapshot | You need the state right before the run, and Time Machine’s last copy may be up to an hour old. Git only covers tracked files, see undo Claude Code changes. |
| Bulk-rename or reorganize a folder | Folder snapshot | The undo point only matters for the next few minutes. |
| Update the system or install something big | Time Machine, after Back Up Now | The risk is to the whole Mac, not one folder. |
| Delete things you might want in three weeks | Time Machine | It keeps daily and weekly copies; a snapshot you made today will be gone or forgotten. |
| Worry about the disk dying | Time Machine | Only a backup on another disk helps. |
A snapshot without hand-typed commands
Taking a snapshot by hand with cp -c works. You have to remember to do it, compare the two folders yourself afterwards, and delete old copies. Mulligan automates that part: it saves a folder as an APFS clone in one click or with mulligan save ., shows every file that changed, was removed or was added since, and puts back the whole folder or just the files you pick. Putting back saves the current state first, so you can undo the undo. In our tests on macOS 27.0.1, saving 20,000 files plus a 1 GB file took about two seconds.
It isn’t a backup, for the same reason a hand-made clone isn’t: it’s on the same disk. Keep Time Machine on.
One more option: ask Time Machine for a local snapshot
The tmutil man page lists tmutil localsnapshot, which creates local Time Machine snapshots of the APFS volumes included in the backup. That gives you an on-demand restore point without the backup disk. We haven’t tested restoring from one for this guide, and Apple says local snapshots disappear within 24 hours, so treat it as a short-term safety net.
Questions
Can I make Time Machine back up right before a risky change?
Yes. With the backup disk connected, choose Back Up Now from the Time Machine menu in the menu bar. It backs up the whole Mac, so how long it takes depends on how much has changed.
How long does Time Machine keep local snapshots on the Mac?
Apple says local snapshots are removed when the Mac needs the space or when they are older than 24 hours. They are only made on APFS disks, and the Mac needs plenty of free space.
Is a folder snapshot a replacement for Time Machine?
No. A snapshot made with an APFS clone sits on the same disk as the folder, so it can't protect you from a failed or lost disk. Use it as a quick undo point and keep Time Machine for backups.
Why doesn't Time Machine show the state from five minutes ago?
Time Machine only has the moments it backed up. Apple says it keeps hourly backups for the past 24 hours, so a change made between two backups has no copy of the state just before it.