Not enough storage to install a macOS update

Why it happens

A macOS update needs room for the download and extra working space while it installs, so it asks for more than the download size. Big yearly upgrades need far more room than small fixes. When the disk is nearly full, the installer stops before it starts so nothing gets damaged.

How to fix it

1. Click the Apple menu, choose System Settings, then click General in the sidebar and open Storage. Give the coloured bar a moment to fill in. It shows how much space is free.

   General›Storage

2. Under the bar, look at the recommendations. Store in iCloud and Optimize Storage can free a lot of space quickly. Read what each one does before you turn it on.

3. In the list below, click the info button next to the biggest categories, such as Applications or Documents, and sort by size. Before you delete anything here, know that Storage deletes it straight away, without the Trash, and you can't undo it. Then remove apps you no longer use, old downloads and large videos you've already copied somewhere safe.

   General›Storage›Documents

4. Empty the Trash, because files there still take up space. Control-click the Trash in the Dock and choose Empty Trash. This is permanent, so check nothing important is inside first.

5. Restart your Mac. This clears temporary files and lets macOS release space it was holding on to.

6. Open Software Update again and click Update Now or Upgrade Now. Try to free a little more than the update asks for, so the install has room to work.

   General›Software Update

Still not fixed?

1. Old iPhone and iPad backups can be huge. In Storage, click the info button next to iOS files and delete backups for devices you no longer use. These are deleted straight away, too.

   General›Storage›iOS files

2. A big Photos library is often the largest item. If you use iCloud Photos, open Photos, then Settings, then iCloud, and choose Optimize Mac Storage. Your full library has to fit in your iCloud storage plan.

   Photos›Settings›iCloud›Optimize Mac Storage

3. Move large folders, like video projects or old photo exports, to an external drive. Copy them, check they open from the drive, then delete them from your Mac and empty the Trash.

4. If the download gets going but then stalls, keep the Mac plugged in and on Wi-Fi, restart, and open Software Update again later. Apple's servers can be slow on release days.

5. If Storage shows plenty of free space but the update still says there isn't enough, or System Data keeps growing after a restart, contact Apple Support. They can check the disk and help you install the update another way.