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Question: MacOS Startup Progress Bar Stuck At 100%

My machine is a late 2015 iMac with eight gigs of memory and an Intel I5 running the latest public release of MacOS High Sierra.

I restarted my Mac yesterday evening and found that after about two hours it had still not gotten past the startup screen. The bar remained at 100% full. I left it overnight hoping it would sort itself out, but to my dismay I found this morning that it still hadn't changed. I tried booting into safe mode but that unfortunately still gave the same result. I'm unsure of what to do next, and worry I may lose some potentially unsaved files. I also do not have a Time Machine backup with which to revert to, (most of my files were stored in iCloud thankfully).

iMac, macOS High Sierra (10.13.3)

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Mar 14, 2018 12:16 PM in response to jacob-m-h In response to jacob-m-h

Top 10 Troubleshooting Tips for Mac Startup Problems

Troubleshooting Startup and Login Items

How to Fix a Mac That Stalls on the Gray or Black Screen at Startup

How to abort a macOS installation loop

[A solution provided by user danbeacs. I have edited where needed.]

I noticed a lot of people having trouble with this.


When you've downloaded Mac OS Sierra on your MacBook but either the file is corrupted or you've run out of disk space, it's nearly impossible to get out of the loop by restarting your computer.


When you reboot, a dialogue box saying “Mac OS cannot be installed” may pop up. Click anywhere on the box and the top menubar will appear. Open Disk Utility and select the grayed out Macintosh HD (or whatever you have named your startup disk,) then press “Mount” - this will take a few moments. If you want to hedge your bet, click on Mac OS Sierra and select “First Aid”, to try and repair any issues with it.


Once your startup drive appears as a mounted drive, go back into the top menu, click the Apple Menu and select “Startup Disk.” The Mac’s HDD should appear. Select it, and then you can click “Restart’” on the installation box.


A nightmarish problem with a fairly simple solution. I learned the hard way. I hope this helps.

Mar 14, 2018 12:16 PM

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Mar 14, 2018 1:16 PM in response to Kappy In response to Kappy

I have tried your troubleshooting methods with no luck. I still cannot get past the startup screen with the full progress bar. I also do not get a grey dialogue box saying “MacOS cannot be installed”. I checked Disk Utility via booting into recovery and my main HD is already mounted and appears to be functioning correctly. I believe the issue may have something to do with the latest update, (although I could be wrong) as I have had no issues with High Sierra up until yesterday.

Mar 14, 2018 1:16 PM

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Mar 14, 2018 1:33 PM in response to jacob-m-h In response to jacob-m-h

Did you read through the three links for a solution or just try the last item? If you've been through everything without success, then you will need to try the following:


Install El Capitan or Later from Scratch


If possible backup your files.


  1. Restart the computer. Immediately after the chime hold down the CommandandRkeys until the Apple logo appears. When the Utility Menu appears:
  2. Select Disk Utility from the Utility Menu and click on Continue button.
  3. When Disk Utility loads select the volume (indented entry, usually Macintosh HD) from the Device list.
  4. Click on the Erase icon in Disk Utility's main window. A panel will drop down.
  5. Set the Format type to APFS (SSDs only) or Mac OS Extended (Journaled.)
  6. Click on the Apply button, then wait for the Done button to activate and click on it.
  7. Quit Disk Utility and return to the Utility Menu.
  8. Select Install OS X and click on the Continue button.


This will install the version of OS X you had installed.

Mar 14, 2018 1:33 PM

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Question: MacOS Startup Progress Bar Stuck At 100%