DiskSpace AI

Not enough space to update macOS? How to make room safely

In short

Major macOS updates usually need around 25–35 GB free. If Finder says you have room but the update still fails, it's often “purgeable” space and Time Machine snapshots. Start there, then clear what recreates itself (caches, old installers, build data) before touching your own files.

How much space does a macOS update need?

It depends on the version and your Mac, but a major update (for example, from one yearly version to the next) usually asks for 25–35 GB of free space: the download plus room to unpack and install it. Minor updates need much less. Software Update tells you the exact amount when it says there isn't enough space, so write that number down: it's your goal.

Why it fails even though Finder shows free space

Finder counts purgeable space as available: things macOS can delete by itself when it needs to, like local Time Machine snapshots and iCloud files that are already in the cloud. The installer doesn't always wait for macOS to free them, so you can have “40 GB available” and still get the error.

Local Time Machine snapshots are the usual suspect. macOS keeps them for about 24 hours, and they can hold many gigabytes if you recently deleted or changed big files. To see them, open Terminal and run:

tmutil listlocalsnapshots /

The simplest way to free them is to restart your Mac or let Time Machine finish a backup. If you need the space right now, this deletes the local snapshots of your disk (your Time Machine backups on the external drive aren't touched):

sudo tmutil deletelocalsnapshots /

Step 1: the quick wins (nothing you need)

Step 2: what recreates itself (caches and build data)

Many big folders are copies that apps and tools make again when they need them. Deleting them loses nothing:

The catch is knowing which folders are really caches. That's what the folder guide is for: what each one is and whether you can delete it.

Step 3: big things that need a decision

Step 4: move instead of delete

If you still need room, move things instead of deleting them: photos and videos to an external drive, or turn on Store in iCloud in System Settings → General → Storage, so files already in iCloud only download when you open them.

Once the update is installed, the installer deletes itself and you get that space back.

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Folders in this guide

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