Your Mac won’t boot. You remember there’s a magic key combo that fixes things. Was it Command-R? Option-Command-P-R? Let’s end the guessing game.

Most common startup key combinations

Hold these keys immediately after pressing power until you see the described screen:

KeysPurposeWhen to use
⌘ + RRecovery ModeReinstall macOS, restore from Time Machine, disk repair
⌥ + ⌘ + P + RReset NVRAM/PRAMBoot issues, display problems, sound issues
ShiftSafe ModeTroubleshoot startup issues, kernel extensions
⌥ (Option)Startup ManagerChoose boot disk, boot from USB
DApple DiagnosticsHardware testing
⌥ + DInternet DiagnosticsHardware testing via internet
⌘ + SSingle User ModeTerminal-only boot for advanced repairs
⌘ + VVerbose ModeSee detailed boot process messages
TTarget Disk ModeUse Mac as external hard drive

NVRAM/PRAM Reset (most common)

When: Fixes boot issues, display resolution problems, time zone resets, sound issues, kernel panics.

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1. Shut down Mac
2. Press power button
3. IMMEDIATELY press and hold: ⌥ + ⌘ + P + R
4. Keep holding until you hear startup chime TWICE (or see Apple logo appear and disappear twice)
5. Release keys

For Macs with T2 chip: Hold for ~20 seconds, then release.

SMC Reset (System Management Controller)

When: Fan running constantly, battery not charging, power button not responding, sleep/wake issues.

MacBook with removable battery (pre-2009):

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1. Shut down Mac
2. Remove battery
3. Press and hold power button for 5 seconds
4. Reinsert battery and turn on

MacBook with non-removable battery (2009-2017):

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1. Shut down Mac
2. Press Shift + Control + Option (left side) + Power button
3. Hold for 10 seconds
4. Release all keys and turn on normally

MacBook with T2 chip (2018+):

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1. Shut down Mac
2. Press and hold power button for 10 seconds
3. Release, wait a few seconds
4. Press power button to turn on

iMac, Mac Mini, Mac Pro:

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1. Shut down Mac
2. Unplug power cord
3. Wait 15 seconds
4. Plug back in and wait 5 seconds
5. Press power button

Recovery Mode details

⌘ + R - Install latest macOS that was on your Mac ⌥ + ⌘ + R - Upgrade to latest compatible macOS ⇧ + ⌥ + ⌘ + R - Install macOS that came with your Mac

Safe Mode

When: App crashes on startup, kernel extension issues, font problems, login screen problems.

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1. Shut down Mac
2. Press power button
3. IMMEDIATELY press and hold Shift
4. Release when you see login window (gray screen on older Macs)

What Safe Mode does:

  • Verifies and repairs startup disk
  • Loads only essential kernel extensions
  • Disables startup items and login items
  • Deletes font caches, kernel cache

Quick troubleshooting guide

Mac won’t boot:

  1. Try NVRAM reset first (⌥ + ⌘ + P + R)
  2. If that fails, boot to Recovery (⌘ + R) and run Disk Utility

Mac boots but behaves strangely:

  1. Try Safe Mode (Shift)
  2. If works in Safe Mode, problem is likely a startup item or kernel extension

Hardware issues (fans, battery, power):

  1. Reset SMC (see instructions above based on your model)

Need to reinstall macOS:

  1. Boot to Recovery (⌘ + R)
  2. Choose “Reinstall macOS”

Pro tip: For most boot issues, start with NVRAM reset (⌥ + ⌘ + P + R). It’s quick, safe, and fixes 80% of weird boot problems. If that doesn’t work, boot to Recovery Mode (⌘ + R) and run Disk Utility First Aid.