Time Machine local snapshots are taking space on the internal drive
· 5 min read
When Time Machine is turned on, macOS takes an hourly snapshot of your data volume and stores it on the internal drive, not on the backup disk. That is deliberate: it means you can restore a file you ruined this morning while the backup drive is sitting in a drawer at home.
It also means the space you thought you freed by deleting a large folder is still being held, because a snapshot from earlier today still refers to it. The snapshots are meant to be reclaimed automatically, and usually are, but on a disk that has been near full for weeks the automatic behavior is not fast enough to be reassuring.
What a local snapshot actually is
An APFS snapshot is a frozen record of the state of the volume at a moment in time. It does not copy your files. It just tells the file system that the blocks belonging to that moment cannot be reused yet.
The consequence is the thing people find confusing: a snapshot costs almost nothing when it is taken and grows as you change things afterwards. Delete 60 GB of video and the snapshot taken an hour earlier now holds 60 GB of blocks that cannot be released. Your disk shows no more free space than it did before. Nothing has gone wrong.
macOS thins these on its own. It keeps them for around a day, and it removes them more aggressively when free space runs low. It also takes one before installing a macOS update, so you can be rolled back if the update fails.
See what you have
Open Terminal.
tmutil listlocalsnapshots /
You will get lines in one of two shapes. com.apple.TimeMachine.2026-09-09-101530.local is an ordinary hourly snapshot, with the date and time in the name. com.apple.os.update- followed by a long hexadecimal string is a snapshot taken around a system update.
For just the dates, in a form the deletion command accepts:
tmutil listlocalsnapshotdates
To see the same thing from the file system’s side, including any volume you did not think to check:
diskutil apfs listSnapshots /System/Volumes/Data
Knowing how many you have does not tell you what they cost, because that depends entirely on how much has changed since each one. There is no command that prints a per-snapshot size honestly. What you can see is the total held back, which shows up as purgeable space in Finder’s Get Info on the disk, and inside System Data in System Settings.
Reclaim the space
Two commands, and the gentler one first.
Thin them. This asks macOS to delete oldest-first until it has recovered roughly the number of bytes you ask for:
sudo tmutil thinlocalsnapshots /System/Volumes/Data 20000000000 4
The number is the amount to reclaim in bytes (20000000000 is about 20 GB). The final value is urgency, from 1 to 4; 4 tells macOS to try hardest. Run it, then check free space again. This is the option to use, because it removes the oldest restore points and keeps the recent ones.
Delete one by date, if you know which:
sudo tmutil deletelocalsnapshots 2026-09-09-101530
Delete all of them for a volume, which you should only do when you are genuinely short and understand what you are giving up:
sudo tmutil deletelocalsnapshots /System/Volumes/Data
After any of these, free space in Finder may take a minute to update, and the Storage pane in System Settings will lag longer than that. Restart if the number bothers you.
Snapshots taken around a system update generally clear themselves once the update has completed and the Mac has restarted a couple of times. If one is still there weeks later, it is safe to remove with the same commands.
Stop them piling up again
Removing snapshots is a repair, not a fix. Three things reduce how much space they hold in the first place.
- Connect the backup disk more often. Once a backup completes, the corresponding local snapshots have done their job and are thinned out. A Mac that has not seen its backup drive since last month is the classic case.
- Exclude folders that churn. System Settings, General, Time Machine, Options, then add to the exclusion list. Exclusions apply to local snapshots too, which is the part people miss. Virtual machine disk images, container images, build folders and simulator data change constantly and are usually rebuildable, so excluding them removes both backup bloat and snapshot bloat. What System Data is on a Mac covers where those folders live.
- Change the backup frequency in the same Options panel. Hourly is the default; daily is a reasonable choice on a machine that is short of space, and Manually stops automatic snapshots entirely.
Turning Time Machine off altogether stops snapshots, and that is the trade you are actually making: disk space now, in exchange for no backup at all. It is almost never the right answer. If you are tempted, get an external drive first.
If you want to see what snapshots are costing you alongside everything else, Crumb reports local snapshots on the internal drive as part of its read-only audit, next to the System Data breakdown, iOS backups and swap, so you can tell in one look whether snapshots are your problem or a distraction from the real one.
When it is not the snapshots
It is easy to blame snapshots for any missing space, because the mechanism is obscure enough to sound plausible.
If tmutil listlocalsnapshots / prints nothing but a header, you have no local snapshots and the space is elsewhere. If it prints two and you are missing 300 GB, they are not the answer either. The Mac says storage is full, but the folders do not add up works through the other places to look, and purgeable space explains the accounting that makes snapshots look larger than they are.
Questions
Will deleting local snapshots delete my Time Machine backups? No. The backups on the external disk are untouched. You are removing the copies held on the internal drive, so you lose the ability to restore recent versions without connecting the backup drive.
Why did the space not come back immediately?
Free space accounting on APFS updates lazily, and the Storage pane in System Settings lags further behind still. Check with df -h /System/Volumes/Data rather than the graph, and restart if you want the figures to settle at once.
Can I stop local snapshots but keep Time Machine backups? Not separately. Snapshots are how Time Machine builds a consistent backup. Setting the frequency to Manually gets close: snapshots are then taken when a backup runs rather than every hour.
Do local snapshots run on a Mac with no backup disk configured? If Time Machine has never been set up, no. If it was set up and the disk is simply absent, yes, and that is precisely the situation where they accumulate.