Time Machine Local Snapshots Eating Storage? How to Clear Them

What Are Time Machine Local Snapshots?

Most people think of Time Machine as something that only writes to an external drive or a network backup destination. That is only half the story. Since macOS High Sierra introduced the APFS file system, Time Machine also creates local snapshots that live directly on your Mac's internal drive — completely separate from your external backups.

A local snapshot is a point-in-time, read-only capture of your entire startup volume. It exists so that if your external backup disk is not connected, macOS still has a recent recovery point on the internal SSD. If you accidentally delete a file and your Time Machine drive is not plugged in, you can still "Enter Time Machine" and restore it from a local snapshot. macOS takes one roughly every hour while Time Machine is enabled, and additional snapshots before major system events like an OS update.

These snapshots use APFS's copy-on-write mechanism. When a snapshot is created, it does not immediately duplicate your data — it simply records the current state of the file system. Space is only consumed as files change or get deleted afterward, because the old versions of those blocks must be retained so the snapshot stays valid.

Why Local Snapshots Count as "Purgeable" Space

If you have ever opened Apple menu > System Settings > General > Storage (or the older "About This Mac > Storage" screen) and seen a chunk of space labeled Purgeable, local snapshots are very often the reason. Purgeable space is storage that macOS considers reclaimable — data it can and will delete automatically when the system needs the room for something else.

Local snapshots are the textbook example of purgeable data. By design, macOS thins them out automatically: they are normally retained for 24 hours, and older ones are deleted after that window. On top of that, macOS aggressively removes snapshots the moment free space drops below a threshold, so you should almost never run out of disk space purely because of them.

This is why disk-usage numbers can look contradictory. Finder's "Get Info" might show 80 GB used on a 512 GB drive, while a command-line tool like df -h reports far less free space than you expected. The gap is the purgeable local-snapshot data that macOS is holding onto but is willing to release on demand.

How to See Your Local Snapshots with tmutil

The tool for working with Time Machine from the command line is tmutil, which ships with every copy of macOS. To list the local snapshots currently stored on your startup volume, open Terminal (in Applications > Utilities) and run:

tmutil listlocalsnapshots /

The output is a list of snapshot identifiers that look like this:

com.apple.TimeMachine.2026-09-03-091500.local

The long number embedded in each name is a timestamp in YYYY-MM-DD-HHMMSS format, so you can read exactly when each snapshot was taken. If you see several entries spanning the last day, that is completely normal — macOS keeps roughly hourly snapshots for the past 24 hours.

To understand how much space these snapshots and other purgeable data are occupying, you can inspect the volume directly:

diskutil apfs list

Look for the "Capacity In Use By Snapshots" line under your data volume. You can also check overall free versus purgeable space with df -h / and compare it against what Finder reports.

How to Delete Time Machine Local Snapshots

There are two supported approaches: deleting snapshots individually, or asking macOS to thin them in bulk. Quit any heavy backup or disk-imaging tasks before you begin, and make sure your regular external Time Machine backup is up to date if you rely on it.

1. 1
   Open Terminal. Launch it from Applications > Utilities, or press Command + Space and type "Terminal".
2. 2
   List existing snapshots. Run tmutil listlocalsnapshots / to see the timestamps of every snapshot on your startup volume.
3. 3
   Delete one specific snapshot. Use the timestamp portion of the name: tmutil deletelocalsnapshots 2026-09-03-091500. macOS removes that single snapshot and frees the associated purgeable space.
4. 4
   Or thin snapshots in bulk. To let macOS reclaim a target amount of space, run tmutil thinlocalsnapshots / 21474836480 4. The number is bytes to purge (20 GB here) and the final digit is the urgency level (1–4, where 4 is most aggressive).
5. 5
   Verify the space was freed. Run tmutil listlocalsnapshots / again to confirm the snapshots are gone, and check df -h / to see the reclaimed free space.

Deleting local snapshots does not touch your real files and does not affect the full backups stored on your external Time Machine drive. You are only removing the temporary on-device recovery points. The only trade-off is that, until the next hourly snapshot is taken, you have fewer local restore points if your external drive is disconnected.

When Do Local Snapshots Clear Automatically?

In most cases you never have to think about local snapshots because macOS manages them for you. They clear automatically under several conditions:

• After 24 hours. The standard retention window for local snapshots is one day. Snapshots older than that are thinned out during normal Time Machine housekeeping.
• When free space runs low. If your available storage drops below what macOS needs, the system immediately purges snapshots to make room — which is exactly why they are classified as "purgeable."
• When Time Machine is disabled. Turning off Time Machine stops new snapshots from being created and lets existing ones expire.
• Before major operations. macOS may clear or consolidate snapshots ahead of system updates and certain disk operations.

Because of this, manually deleting snapshots is a "right now" tool, not a routine maintenance task. If your storage bar simply looks fuller than expected but you are not actually short on space, the safest move is to do nothing and let macOS reclaim the space when it needs to.

Reclaiming Snapshot and Purgeable Space with TrimyMac

Working with tmutil is powerful but unforgiving — a mistyped timestamp does nothing, and it is easy to lose track of how much space you actually recovered. TrimyMac gives you a clear, visual view of what is consuming your disk, including purgeable data driven by local snapshots, and lets you trigger a cleanup without memorizing commands.

Instead of hopping between Terminal, System Settings, and Finder to reconcile conflicting storage numbers, TrimyMac surfaces the real picture in one place: how much space is genuinely in use, how much is purgeable, and where the biggest reclaimable chunks live. It performs the safe, supported operations under the hood so you get the free space you need without risking your actual data or your external backups.