My Mac says the disk is full, but Finder shows free space

Q: Why are there two numbers?

macOS gives apps two answers when they ask about space: Free: space no file is using right now. Available: free space plus purgeable space, which macOS removes on its own when a file needs the room. On the Mac this page was written on, the same disk at the same moment had 154.8 GB free and 368.7 GB available. Finder shows the larger kind of number; an installer that checks free space first may see only the smaller one.

Q: How do I see the real free space?

df -h / diskutil info / | grep "Container Free Space" Both show what is free right now, without purgeable space. df counts in binary units (Gi), so its number looks smaller than Finder's for the same bytes.

Q: What is purgeable space?

Local Time Machine snapshots, kept on the Mac while the backup disk isn't connected. List them with tmutil listlocalsnapshots /. iCloud Drive and Photos files that are also in iCloud, with Optimize Mac Storage on. Some caches macOS knows it can rebuild.

Updated November 3, 2026

An installer or update says there isn't enough space, yet Finder says you have plenty. Both are telling the truth: they are reading different numbers.

The short answer: macOS counts purgeable space (local Time Machine snapshots, iCloud files kept offline, some caches) as available, because it can remove it when needed. Some apps only look at what is free right now. Check the real free space with df -h /; to turn purgeable space into free space, thin the local snapshots and restart.

Why are there two numbers?

macOS gives apps two answers when they ask about space:

Free: space no file is using right now.
Available: free space plus purgeable space, which macOS removes on its own when a file needs the room.

On the Mac this page was written on, the same disk at the same moment had 154.8 GB free and 368.7 GB available. Finder shows the larger kind of number; an installer that checks free space first may see only the smaller one.

How do I see the real free space?

df -h /
diskutil info / | grep "Container Free Space"

Both show what is free right now, without purgeable space. df counts in binary units (Gi), so its number looks smaller than Finder's for the same bytes.

What is purgeable space?

Local Time Machine snapshots, kept on the Mac while the backup disk isn't connected. List them with tmutil listlocalsnapshots /.
iCloud Drive and Photos files that are also in iCloud, with Optimize Mac Storage on.
Some caches macOS knows it can rebuild.

How do I turn purgeable space into free space?

Connect your Time Machine disk and let a backup finish, or remove local snapshots with tmutil thinlocalsnapshots / 999999999999 4.
Restart the Mac: temporary files and swap are cleared.
Run df -h / again. If free space is still too small, remove something you no longer need: System Settings › General › Storage lists the biggest categories.

Why does the installer still say there isn't enough space?

A macOS update needs room for the download and for preparing it, which is more than the download size shown. Make room until the free number from df is comfortably larger, not only the available one.