Imac Shuts Down During Boot

These key combinations only apply to Mac computers with an Intel processor, not Mac computers with Apple Silicon.

To use any of these key combinations, press and hold the keys immediately after pressing the power button to turn on your Mac, or after your Mac begins to restart. Keep holding until the described behaviour occurs.

Shuts down at boot: In this scenario, your Mac does turn on, but shuts down by itself during boot. Question mark folder icon: This is likely a hard drive issue. A folder with a question mark on it means that your startup disk is not working or that your device can't find a working operating system on it.

• Command (⌘)-R: Start up from the built-in macOS Recovery system. Or use Option-Command-R or Shift-Option-Command-R to start up from macOS Recovery over the Internet. macOS Recovery installs different versions of macOS, depending on the key combination you use while starting up. If your Mac is using a firmware password, you're prompted to enter the password.
  
• Option (⌥) or Alt: Start up to Startup Manager, which allows you to choose other available startup disks or volumes. If your Mac is using a firmware password, you're prompted to enter the password.
  
• Option-Command-P-R:Reset NVRAM or PRAM. If your Mac is using a firmware password, it ignores this key combination or starts up from macOS Recovery.
• Shift (⇧): Start up in safe mode. Disabled when using a firmware password.
• D: Start up with the Apple Diagnostics utility. Or use Option-Dto start up this utility over the Internet. Disabled when using a firmware password.
• N: Start up from a NetBoot server, if your Mac supports network startup volumes. To use the default boot image on the server, hold down Option-N instead. Disabled when using a firmware password.
• Command-S: Start up in single-user mode. Disabled in macOS Mojave or later, or when using a firmware password.
• T: Start up in target disk mode. Disabled when using a firmware password.
• Command-V: Start up in verbose mode. Disabled when using a firmware password.
• Eject (⏏) or F12 or mouse button or trackpad button: Eject removable media, such as an optical disc. Disabled when using a firmware password.

Imac Shuts Down During Safe Boot

If a key combination doesn't work

If a key combination doesn't work during startup, one of these solutions may help:

• Locate the 'Command', 'Option', 'P', and 'R' keys on your Keyboard. Turn on your Computer, and before the Gray Screen appears, hold down Command-Option-P-R. Keep holding this down till you hear the start up chime 3 times.
• If a key combination doesn't work during startup, one of these solutions may help: Press and hold all of the keys in the combination together, not one at a time. Shut down your Mac. Then press the power button to turn on your Mac. Then press and hold the keys as your Mac starts up.
• Reboot your Mac and hold the T key down when you hear the boot chimes to get to Target Disk mode. Attach your Mac to another one using a FireWire or Thunderbolt cable. Open Disk Utility on your second Mac. Hold the Command key and click both the boot volume and drive device on your first Mac to select them.

• Press and hold all of the keys in the combination together, not one at a time.
• Shut down your Mac. Then press the power button to turn on your Mac. Then press and hold the keys as your Mac starts up.
• Wait a few seconds before pressing the keys, to give your Mac more time to recognise the keyboard as it starts up. Some keyboards have a light that flashes briefly at startup, indicating that the keyboard is recognised and ready for use.
• If you're using a wireless keyboard, plug it into your Mac, if possible. Or use your built-in keyboard or a wired keyboard. If you're using a keyboard made for a PC, such as a keyboard with a Windows logo, try a keyboard made for Mac.
• If you're using Boot Camp to start up from Microsoft Windows, set Startup Disk preferences to start up from macOS instead. Then shut down or restart and try again.

Remember that some key combinations are disabled when your Mac is using a firmware password.

Learn more

• Keyboard shortcuts you can use after your Mac has started up.

This page covers 5 fixes for Mac won't boot or start issue after macOS Big Sur, Catalina, Sierra or older macOS update issue. If you are with this issue, follow to make your Mac computer work now:

macOS has now been updated to 11.0, and many Mac users are trying to upgrade to the newest version. While for most it's a usual pleasurable experience, for some this update had downsides. Some users complain that their Mac computers won't boot after installing new macOS Big Sur/Catalina. When Mac fails, it usually can't boot or start up properly. If you are faced with this situation, the most important thing should be recovering data from the unbootable Mac because:

• Your attempts to fix the Mac not booting issue may write new data on this Mac, which will overwrite the old data and make it irrecoverable.
• Recovering data before the complex fixes can avoid data loss.

EaseUS Mac data recovery software is able to recover data from unbootable Macs after update. It creates a bootable media that enables you to recover data from Mac hard drive (If you only have one Mac). What's more, it recovers data from failed internal Mac hard drive, APFS boot drive, and unmountable APFS boot volume, etc. If you have two Mac devices, take out the hard drive and connect it to the other Mac. Download EaseUS Data Recovery Wizard for Mac on that Mac device, and recover data from the hard drive.

Then, you can read on and Fix the 'Mac won't boot after update' issue after you have successfully got data from the drive.

1. Reset the PRAM / NVRAM

NVRAM refers to special memory sections on your Mac that store data that persists even when the Mac is shut off, such as volume settings and screen resolution. Unraid sync folders. Resetting that data isn't harmful! In some cases, after performing this step, your Mac will restart normally.

• Restart your Mac
• Hold down all of these keys: 'Command', 'Option', 'P' and 'R', and turn on the Mac. (It's the same keys to reset the PRAM).
• Keep holding the keys down until you hear the Mac restart again.

You may see a progress bar on startup. If the progress bar fills up and then the Mac starts up, you're probably good to go. If not, reset SMC. Caught off.

Force Shutdown Windows 10

2. Reset the SMC

In some situations, you may need to reset your Mac's SMC (System Management Controller).

• Shut the Mac down.
• Unplug all cables.
• Wait for a few minutes.
• Plug the cables back in and start up the Mac.

If you've got a Mac desktop, unplug it for 15 seconds and then plug it in and after five seconds press the power button.

3. Boot Mac in Safe Mode

Imac Shuts Down During Boot Up

Safe Mode is a stripped-down version of the Mac operating system that can be useful if you are trying to troubleshoot issues with your Mac.

• Start your Mac, press and hold the 'Shift' key, and make sure your Mac has at least 9 GB of free space.
• When the login window appears to release the shift key and log in. You may be required to log in twice if you have FileVault turned on. Then restart the device.

Imac 2011 Shuts Off While Booting Up

Viewbotting. Wait patiently till Mac computer finish the reboot process.

Mac Shuts Down During Boot

4. Run Disk Utility in Recovery Mode

If your Mac is booting but the operating system isn't loading up, you may have a corrupted drive. Luckily it is possible to fix this in Recovery Mode. In Recovery Mode you can restore from a Time Machine backup, use Disk Utility to verify and repair connected drives, check your internet connection, get help online using Safari, and install or reinstall macOS.

Why Imac Shuts Down By Itself

• Make sure the Mac is off. If it's stuck on a grey, blue or white screen, just hold down Mac's power button for several seconds until it shuts off.
• Hold down the 'Command' and 'R' keys, and power the Mac back up again. Keep pressing 'Cmd' + 'R' while your Mac is booting up.
• Once your Mac starts in Recovery Mode you can have access to 'Utilities'. Click 'Disk Utility', locate the icon for your Mac's drive, and click 'Verify Disk'.

5. Reinstall macOS Big Sur/Catalina/Sierra

The last method to fix macOS Big Sur, Catalina or Sierra fails to boot after update error is to reinstall macOS.

• You can download wanted macOS Big Sur/Catalina/Sierra and create a bootable USB drive to clean install macOS Big Sur/Catalina/Sierra on your computer again.
• You can also boot into Recovery mode (Solution 4), and then click to install the latest OS and follow the onscreen prompts. Our article on resetting a Mac to factory settings has more information on reinstalling macOS.

Imac Shuts Down During Boot

• Command (⌘)-R: Start up from the built-in macOS Recovery system. Or use Option-Command-R or Shift-Option-Command-R to start up from macOS Recovery over the Internet. macOS Recovery installs different versions of macOS, depending on the key combination you use while starting up. If your Mac is using a firmware password, you're prompted to enter the password.
  
• Option (⌥) or Alt: Start up to Startup Manager, which allows you to choose other available startup disks or volumes. If your Mac is using a firmware password, you're prompted to enter the password.
  
• Option-Command-P-R:Reset NVRAM or PRAM. If your Mac is using a firmware password, it ignores this key combination or starts up from macOS Recovery.
• Shift (⇧): Start up in safe mode. Disabled when using a firmware password.
• D: Start up with the Apple Diagnostics utility. Or use Option-Dto start up this utility over the Internet. Disabled when using a firmware password.
• N: Start up from a NetBoot server, if your Mac supports network startup volumes. To use the default boot image on the server, hold down Option-N instead. Disabled when using a firmware password.
• Command-S: Start up in single-user mode. Disabled in macOS Mojave or later, or when using a firmware password.
• T: Start up in target disk mode. Disabled when using a firmware password.
• Command-V: Start up in verbose mode. Disabled when using a firmware password.
• Eject (⏏) or F12 or mouse button or trackpad button: Eject removable media, such as an optical disc. Disabled when using a firmware password.

Imac Shuts Down During Safe Boot

If a key combination doesn't work

If a key combination doesn't work during startup, one of these solutions may help:

• Locate the 'Command', 'Option', 'P', and 'R' keys on your Keyboard. Turn on your Computer, and before the Gray Screen appears, hold down Command-Option-P-R. Keep holding this down till you hear the start up chime 3 times.
• If a key combination doesn't work during startup, one of these solutions may help: Press and hold all of the keys in the combination together, not one at a time. Shut down your Mac. Then press the power button to turn on your Mac. Then press and hold the keys as your Mac starts up.
• Reboot your Mac and hold the T key down when you hear the boot chimes to get to Target Disk mode. Attach your Mac to another one using a FireWire or Thunderbolt cable. Open Disk Utility on your second Mac. Hold the Command key and click both the boot volume and drive device on your first Mac to select them.

• Press and hold all of the keys in the combination together, not one at a time.
• Shut down your Mac. Then press the power button to turn on your Mac. Then press and hold the keys as your Mac starts up.
• Wait a few seconds before pressing the keys, to give your Mac more time to recognise the keyboard as it starts up. Some keyboards have a light that flashes briefly at startup, indicating that the keyboard is recognised and ready for use.
• If you're using a wireless keyboard, plug it into your Mac, if possible. Or use your built-in keyboard or a wired keyboard. If you're using a keyboard made for a PC, such as a keyboard with a Windows logo, try a keyboard made for Mac.
• If you're using Boot Camp to start up from Microsoft Windows, set Startup Disk preferences to start up from macOS instead. Then shut down or restart and try again.

Remember that some key combinations are disabled when your Mac is using a firmware password.

Learn more

• Keyboard shortcuts you can use after your Mac has started up.

This page covers 5 fixes for Mac won't boot or start issue after macOS Big Sur, Catalina, Sierra or older macOS update issue. If you are with this issue, follow to make your Mac computer work now:

macOS has now been updated to 11.0, and many Mac users are trying to upgrade to the newest version. While for most it's a usual pleasurable experience, for some this update had downsides. Some users complain that their Mac computers won't boot after installing new macOS Big Sur/Catalina. When Mac fails, it usually can't boot or start up properly. If you are faced with this situation, the most important thing should be recovering data from the unbootable Mac because:

• Your attempts to fix the Mac not booting issue may write new data on this Mac, which will overwrite the old data and make it irrecoverable.
• Recovering data before the complex fixes can avoid data loss.

EaseUS Mac data recovery software is able to recover data from unbootable Macs after update. It creates a bootable media that enables you to recover data from Mac hard drive (If you only have one Mac). What's more, it recovers data from failed internal Mac hard drive, APFS boot drive, and unmountable APFS boot volume, etc. If you have two Mac devices, take out the hard drive and connect it to the other Mac. Download EaseUS Data Recovery Wizard for Mac on that Mac device, and recover data from the hard drive.

Then, you can read on and Fix the 'Mac won't boot after update' issue after you have successfully got data from the drive.

1. Reset the PRAM / NVRAM

NVRAM refers to special memory sections on your Mac that store data that persists even when the Mac is shut off, such as volume settings and screen resolution. Unraid sync folders. Resetting that data isn't harmful! In some cases, after performing this step, your Mac will restart normally.

• Restart your Mac
• Hold down all of these keys: 'Command', 'Option', 'P' and 'R', and turn on the Mac. (It's the same keys to reset the PRAM).
• Keep holding the keys down until you hear the Mac restart again.

You may see a progress bar on startup. If the progress bar fills up and then the Mac starts up, you're probably good to go. If not, reset SMC. Caught off.

Force Shutdown Windows 10

2. Reset the SMC

In some situations, you may need to reset your Mac's SMC (System Management Controller).

• Shut the Mac down.
• Unplug all cables.
• Wait for a few minutes.
• Plug the cables back in and start up the Mac.

If you've got a Mac desktop, unplug it for 15 seconds and then plug it in and after five seconds press the power button.

3. Boot Mac in Safe Mode

Imac Shuts Down During Boot Up

Safe Mode is a stripped-down version of the Mac operating system that can be useful if you are trying to troubleshoot issues with your Mac.

• Start your Mac, press and hold the 'Shift' key, and make sure your Mac has at least 9 GB of free space.
• When the login window appears to release the shift key and log in. You may be required to log in twice if you have FileVault turned on. Then restart the device.

Imac 2011 Shuts Off While Booting Up

Viewbotting. Wait patiently till Mac computer finish the reboot process.

Mac Shuts Down During Boot

4. Run Disk Utility in Recovery Mode

If your Mac is booting but the operating system isn't loading up, you may have a corrupted drive. Luckily it is possible to fix this in Recovery Mode. In Recovery Mode you can restore from a Time Machine backup, use Disk Utility to verify and repair connected drives, check your internet connection, get help online using Safari, and install or reinstall macOS.

Why Imac Shuts Down By Itself

• Make sure the Mac is off. If it's stuck on a grey, blue or white screen, just hold down Mac's power button for several seconds until it shuts off.
• Hold down the 'Command' and 'R' keys, and power the Mac back up again. Keep pressing 'Cmd' + 'R' while your Mac is booting up.
• Once your Mac starts in Recovery Mode you can have access to 'Utilities'. Click 'Disk Utility', locate the icon for your Mac's drive, and click 'Verify Disk'.

5. Reinstall macOS Big Sur/Catalina/Sierra

The last method to fix macOS Big Sur, Catalina or Sierra fails to boot after update error is to reinstall macOS.

• You can download wanted macOS Big Sur/Catalina/Sierra and create a bootable USB drive to clean install macOS Big Sur/Catalina/Sierra on your computer again.
• You can also boot into Recovery mode (Solution 4), and then click to install the latest OS and follow the onscreen prompts. Our article on resetting a Mac to factory settings has more information on reinstalling macOS.

Imac Shuts Down During Boot

If your Mac does not respond after trying these tips, contact Apple Support or a certified Apple Repair Center. It's likely there is a problem with your logic board or other internal hardware.