“Time Machine snapshots” sound safe — and they are. But here’s the catch: local snapshots live on your internal disk, not your backup drive. When your backup disk is disconnected or Time Machine is busy, macOS stores snapshots of your system’s state on your SSD, and they stack.

On a Mac whose backup drive has been offline for a while, local snapshots routinely eat 50–100 GB. The weird part: they’re optional, and deleting them is one of the safest cleanups in macOS. Here’s how.

What’s a “local snapshot” exactly?

Time Machine has two jobs:

Back up to your external drive (hourly, daily, weekly retention).
Hold recent local-safe-states on the internal disk so you can “Time Machine back” even when the external drive isn’t attached.

Job #2 is the local snapshot — an APFS snapshot of / stored in the container’s free space. It lets you recover a version of a file from yesterday without the backup drive. Nice feature. Thing is, when the backup drive is gone for a while, macOS keeps waiving the window and snapshots accumulate instead of being trimmed.

How big is yours?

tmutil listlocalsnapshots /

You’ll see lines like com.apple.TimeMachine.<date>-<timestamp>. Count and date of each tell you how deep they’ve grown. To see their total weight:

diskutil apfs listSnapshots /
# or with sudo, the byte-size per snapshot:
sudo du -sh / 2>/dev/null | head -1   # no — better, use the snapshot list:

Honestly the du on your root includes the snapshots but can’t isolate them easily. If tmutil listlocalsnapshots shows 6+ snapshots, they’re the multi-GB chunk hiding in “System Data” or diskfree-anomalies.

Safe to delete? Yes — and here’s the proof

Local snapshots are temporary caching. Apple’s own behavior: macOS aggressively trims them when the disk gets full. They are not your backup. Your actual backup is the external drive’s backups.backupdb — untouched by this cleanup.

So the answer to “is it safe to delete local snapshots?” is a confident yes:

# 1. check what's there
tmutil listlocalsnapshots /

# 2. delete a specific snapshot (from step 1, minus the .local suffix)
tmutil deletelocalsnapshots 2026-09-10-083017

# 3. or delete them all, in a loop, over the exact list from step 1:
tmutil listlocalsnapshots / | awk '{ system("tmutil deletelocalsnapshots "$1) }'

It takes one snapshot name at a time, so the awk loop feeds it each entry from the list. It prunes local snapshots on the internal disk without touching your external backup. Instant, safe, reversible-in-effect (Time Machine will take new snapshots next time it runs).

Why they re-grow and how to slow it

Local snapshots repopulate every time Time Machine runs (while the drive is offline). To keep the internal-disk hog from re-bloating:

Keep the backup drive connected — then local snapshots are rarely needed and short-lived.
Confirm Time Machine has a healthy destination.
Set a sane retention — System Settings → General → Time Machine → your drive → Options → “oldest backups” (you control the backup retention; local snapshots follow the de-facto window).

You can’t disable local snapshots directly (no supported toggle), but keeping the external backup healthy means they stay small.

Where they hide in Settings

If your Storage bar shows a big mysterious block, remember: local snapshots are part of what macOS calls “System Data” (and occasionally the “Other Volumes in Container” APFS bucket). Our explainer on System Data breaks down exactly which System Data subfolders are clearable — snapshots are near the top.

See it, then clear it

Local snapshots are invisible in normal folder listings — you’d never spot them by traversing Finder. The reliable way is tmutil listlocalsnapshots / (terminal), or a disk analyzer that shows APFS snapshots and container volumes.

DiskInsight scans your actual disk — including snapshot weight and hidden directories — and ranks every folder by real bytes. You see exactly what’s “System Data” vs caches vs snapshots, then stage what you want to the Trash. Reversible, reviewable, 100% local, no telemetry.

The 30-second fix

tmutil listlocalsnapshots /
tmutil deletelocalsnapshots /

That’s it. Your internal SSD returns tens of gigabytes, your external Time Machine backups are untouched, and the next backup just rebuilds a healthy small snapshot.

TL;DR: Local snapshots = internal-disk cache, not your backup. Prune them with tmutil listlocalsnapshots / → tmutil deletelocalsnapshots <name> per snapshot, and your free space comes right back.

Get DiskInsight Pro · $9.99 one-time to find the other hidden gigabytes before they find you. Read what System Data really contains next.

Time Machine Local Snapshots Are Eating Your Disk - Free to Delete