Fix a macOS update that fails with 'installation failed' or 'an error occurred'

Why it happens

Most failed updates come from a download that didn't finish, too little free space, or a brief network hiccup. Something that loads when your Mac starts, such as an add-on or security tool, can also get in the way. Safe mode starts your Mac with only the basics, which often lets the update through.

How to fix it

1. Open System Settings, click General, then Storage, and check how much space is free. Big updates need a lot of room, so delete large files you don't need or empty the Trash if space is tight.

   General›Storage

2. Check your internet works by opening a website. Turn off any VPN for now, and plug a Mac laptop into power.

3. Start in safe mode. On a Mac with Apple silicon, shut down, then press and hold the power button until startup options appear. Select your disk, hold Shift and click Continue in Safe Mode. On an Intel Mac, restart and hold Shift until the login window appears.

4. In safe mode, open General > Software Update and click Update Now. Let it finish, then your Mac restarts normally.

   General›Software Update

5. Still failing? Back up with Time Machine if you can, then reinstall macOS from Recovery. On Apple silicon, shut down, hold the power button until Loading startup options appears, click Options, then Continue. On an Intel Mac, hold Command-R as it starts. Choose Reinstall macOS. Your files and apps stay where they are.

Still not fixed?

1. If Software Update says it can't reach Apple's servers, make sure Set time and date automatically is on in Date & Time, then try again.

   General›Date & Time

2. If the update stops partway with a progress bar that hasn't moved for a few hours, hold the power button to turn off, wait a moment, then start up and try again. Keep the Mac on power the whole time.

3. If your Mac is from work or school, security tools it runs can block updates. Ask the people who manage it.

4. If even Reinstall macOS fails, or your Mac won't start up afterwards, contact Apple Support or an Apple Authorized Service Provider. Repeated install failures can point to a storage problem that needs a repair.