Erase and reinstall macOS: give your Mac a clean start

Steps

1. 01

   Back up first, and decide which backup you trust

   • Run a Time Machine backup now, so nothing recent is lost
   • Write down roughly when the trouble started — you will want a backup from before that date
   • Collect what you need to sign back in afterwards: your Apple Account password, your Wi-Fi password, licence keys for paid apps, and any two-factor backup codes

   !Careful: Erasing permanently deletes everything on the Mac. Apple's wording: 'Erasing your Mac permanently will delete the files on it.' There is no undo, so do not start until the backup has finished.

   Why?

   After malware or remote access, a backup made once the trouble had started may carry the problem with it. Keep it for your documents and photos, not as something to restore whole.

   Also see: Set up Time Machine properly

2. 02

   Check which route your Mac can take

   • Apple menu›About This Mac, and note the macOS version and whether it lists a Chip (Apple silicon) or a Processor (Intel)
   • Erase All Content and Settings needs macOS Monterey 12 or later, on a Mac with Apple silicon or the Apple T2 Security Chip — use the next step
   • On anything older, or if that option is not there, skip to the Recovery step after it

   Why?

   Apple recommends Erase All Content and Settings wherever it is available: it is quicker, and it leaves macOS itself in place.

3. 03

   Erase All Content and Settings

   Ventura or later

   • macOS Ventura or later:Apple menu›System Settings›General›Transfer or Reset›Erase All Content and Settings

   Monterey

   • macOS Monterey:Apple menu›System Preferences, then choose Erase All Content and Settings from the System Preferences menu in the menu bar

   • Enter your Mac password and your Apple Account password when asked, and follow the prompts
   • Let it restart; reconnect to Wi-Fi, and to a Bluetooth keyboard or mouse if it asks, so the Mac can activate

   ✓You should see: The setup assistant, as on a new Mac.

   Why?

   This removes your data, settings and apps and keeps the installed macOS, so there is nothing to reinstall afterwards. Go straight to the last step.

4. 04

   Or erase from Recovery, then reinstall macOS

   • Apple silicon: shut down, then press and hold the power button until 'Loading startup options' appears,and click Options›Continue
   • Intel: press the power button and immediately hold Command (⌘) and R until an Apple logo or a spinning globe appears
   • Choose Disk Utility and click Continue, select Macintosh HD in the sidebar, and click Erase
   • Keep the name Macintosh HD and the format APFS, then click Erase Volume Group — or Erase, if that button is not shown — and enter your Apple Account details if asked
   • On Apple silicon, follow the on-screen prompts to finish erasing; the Mac restarts
   • Quit Disk Utility, choose Reinstall macOS, click Continue and follow the prompts

   ✓You should see: The setup assistant once the installation finishes.

   !Careful: Keep the Mac plugged in and connected to the internet, and do not close the lid or let it sleep while macOS installs. Apple notes it may restart several times and show a blank screen for a while; leave it alone.

   Why?

   On an Intel Mac, Apple also lists Mac OS Extended (Journaled) as a format; keep whichever Disk Utility offers by default.

   Also see: Fix a Mac that won't start up

5. 05

   Set it up clean, then bring your files back carefully

   • Go through the setup assistant and sign in with your Apple Account; after a compromise, change that password from another device first
   • Install any macOS update that is offered
   • After malware or remote access, we recommend reinstalling apps fresh from the App Store or the maker's own site, and copying back only your documents and photos
   • To restore from Time Machine instead, open Migration Assistant, choose to transfer from a Time Machine backup, pick a backup dated before the trouble started, and tick only the categories you want

   Why?

   In Migration Assistant, an older backup is behind the disclosure arrow next to the one it offers first. A large transfer can take hours and may look as if it has paused.

   Also see: Think someone got into your accounts? Lock them down on Mac · Keep macOS updated the safe way · Move everything to a new Mac with Migration Assistant