Not enough space to update macOS: how much you need and how to get it

Part of: Mac storage full? Find what is using it and free up space safely (Storage full)

When macOS says there is not enough space to update, the fix is to make more room on the startup disk and try again. First find out how much the update needs, then check what you have, then free the difference with safe steps.

Step 1: find the requirement

Apple publishes the storage requirement for each macOS version on its website, and the update screen in System Settings states how much space it needs. Use those figures, not a rule of thumb, because they change with each release. This guide deliberately gives no fixed number.

An update needs more than its download size. The installer downloads the files, unpacks them, and then installs, and each stage needs room at the same time.

Step 2: check what you have

In Terminal, run:

df -h /System/Volumes/Data

This only reads. The Avail column is your free space. Storage settings (Apple menu > System Settings > General > Storage) shows a similar number, but it can include purgeable space, which macOS releases only when it needs it. If the two numbers differ, trust the lower one when planning an update.

Step 3: make room with safe steps

Work through these and check df again after each one:

1. Empty the Trash after looking inside. The space comes back only then. See why the Trash does not free space until you empty it.
2. Remove old installers and disk images you have already used. See how to delete DMG files.
3. Clear out Downloads. See how to clean up the Downloads folder.
4. Find large files you no longer need. See find large files on a Mac.
5. Move files you want to keep to an external drive, then check that they open before removing the originals.

Safe, Risky, Never

• Safe: the Trash after a look, installers you already used, downloads you have checked, files you have copied elsewhere and tested.
• Risky: old iPhone backups and large files you do not recognise.
• Never: system folders, your Photos library contents, or a folder you cannot name. Deleting the wrong thing is worse than a delayed update.

Step 4: try again

Restart your Mac, then run the update again. A restart gives macOS a chance to release purgeable space. If the update still says there is not enough space, free a little more and retry.

If it still fails

• Check whether local snapshots are holding space: tmutil listlocalsnapshots / lists them, and macOS removes them when it needs room. Mac storage full but no files? explains why this happens.
• Look again at the biggest folders with du -sh ~/* | sort -h.
• Back up before a big update. Having a backup means a problem with the update does not become a problem with your files.

What about the old installer?

After an update, a leftover installer can sit on the disk. Disk images and installers you no longer need are safe to remove, but make sure you do not need them to reinstall.

If you are still short

If you are close, one more safe step and a restart may be enough. If you are far away, the biggest gain can come from moving large personal files, such as old video projects or photo exports, to an external drive. Copy them, check that they open, and only then remove the originals. Do not delete system folders to reach a number. If the update still refuses to start with enough room, look for your macOS version on Apple’s support site. We have not tested every failure case.

Plan the update

Updates go better when you are ready. Make sure your Mac is plugged in. Close apps you do not need, so that nothing is writing to the disk while the installer works. Make a backup of anything you cannot replace, because an update is one of the few moments when a lot of system files change at once.

It also helps to start well before you need the update. If the Mac says it is short on space today, the update will need that room again next time, and the next one after that. Making a comfortable margin once is more useful than scraping together just enough each autumn. Spend a few minutes on the biggest items now and you will save yourself the same search next year.

See where the space is

DiskJoy is our product. It scans the folders you choose and reports allocated bytes, a lower bound that leaves out space shared between files (for example APFS clones). A scan only reads sizes and dates and changes nothing. DiskJoy is pre-alpha and cleanup is not available yet, so you remove things yourself, and it cannot update macOS or free space for the installer on its own. Download DiskJoy for Mac if you want to see where your space is before you start.

Next steps

If your disk is nearly full all the time, read startup disk full: what to do first or the complete guide to freeing up space on a Mac.