If a flashing question mark appears when you start your Mac

If you see a flashing question mark on your Mac's screen at startup, it means your Mac can't find its system software.

If the question mark appears for only a few seconds

If your Mac displays a flashing question mark for a few moments but then continues to start up, you might need to reselect your startup disk in System Preferences.

  1. Choose System Preferences from the Apple menu (), then click Startup Disk.
  2. Click the icon of the disk you normally use to start up your computer. It's usually named Macintosh HD.
  3. Close the System Preferences window.

Your Mac should now start up without the flashing question mark.

If your Mac doesn't start up

If your Mac starts up to a flashing question mark, but then doesn't continue starting up, try these steps.

  1. Turn off your Mac by pressing and holding the power button for a few seconds.
  2. Press the power button once to turn your Mac back on. Immediately press and hold the Command and R keys on your keyboard to start your Mac from macOS Recovery. Keep these two keys held down until you see an Apple logo or globe. 
  3. If prompted, select a Wi-Fi network to connect to the Internet as part of startup.
  4. After the macOS Utilities window appears, choose Startup Disk from the Apple menu.
  5. Select your startup disk, then click Restart.

If you don't see your startup disk in the Startup Disk window, close the window and try the next sections of this article.

If you don't see your startup disk

If you don't see your startup disk in the Startup Disk window, use these steps to see if your startup disk needs directory repair.

  1. Open Disk Utility from the macOS Utilities window.
  2. In the Disk Utility window, select your startup disk (usually named "Macintosh HD") from the left side of the window.

  3. Click the First Aid tab.
  4. Click the Repair Disk button to verify and repair any issues with your startup disk.
  5. After your disk is successfully repaired, quit Disk Utility. 
  6. Choose Startup Disk from the Apple menu. Select your startup disk, then click Restart. If you still don't see your Startup Disk, try reinstalling macOS on your startup disk.

If you don't see your built-in startup disk in the Disk Utility window, or if Disk Utility indicates there's a hardware issue, your Mac might need repair. Make an appointment with an Apple Genius or an Apple Authorized Service Provider for more help.

If Disk Utility can't repair your startup disk

If Disk Utility finds issues with your startup disk that it can't repair, you might need to reformat it. You should back up any important data on your startup disk before erasing it. Erasing your startup disk deletes everything stored on it, including items in your home folder like your documents and items on your desktop.

If you don't have a recent backup of personal data that's stored on your startup disk, you can use these steps to try to back up your data to an external drive:

  1. Connect an external USB, Thunderbolt, or FireWire drive to your Mac. The drive needs to be the same size or larger than your current startup disk. It also needs to be a drive that you can erase.
  2. Use macOS Recovery to erase the external drive, then install macOS onto the external drive. Make sure that you select the external disk as the one you want to erase. Don't select your built-in startup disk, usually named Macintosh HD.
  3. After installation is finished, your Mac automatically restarts from the external drive. When Setup Assistant appears, select the option to migrate your data from another disk. Choose your built-in startup disk as the source to migrate your data from. 
  4. When migration is done, complete the steps of the setup assistant. After the desktop appears, confirm that your data is present on the external drive.

Now that you've made a backup to an external drive, follow these steps:

  1. Use macOS Recovery to erase your built-in startup disk and reinstall macOS. Select the built-in startup disk as the one you want to erase, not the external drive. When installation is finished, your Mac automatically restarts from your built-in startup disk.
  2. After you erase your startup disk and reinstall macOS, your Mac automatically restarts and setup assistant appears. To copy your personal data back to your startup disk, select the option in the setup assistant to migrate your data from an existing Time Machine backup or other disk. Choose the external drive as the source to migrate your data from.

If you're unable to erase your startup disk or reinstall macOS, your Mac might need repair. Make an appointment with an Apple Genius or an Apple Authorized Service Provider for more help.

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