Your Mac hasn’t started the upgrade yet.This article is for one very specific issue that usually affects Macs that have been in service for a long time. Sadly upgrades could fail for multiple reasons. Why check? Just because your upgrade failed does not mean that this is the exact issue.What if you booted your failed Mac into safe mode after having the issue?.How do I clear them out before the upgrade? How can I check how many mdworker files my system has before an upgrade.The macOS stuck progress bar issue has many different situations. This would allow the upgrad to finish properly. If you build a fresh system the file counts for spotlight will be very low. This is the reason why the problem could never be reproduced. In some situations users have reported 500,000 – 2,000,000 files!!! Have more than 20,000 files your upgrade could fail. If folders in multiple directories in the location below /private/var/folders/*/*/C/ If you are upgrading from macOS High Sierra, Mojave, or Catalina to Big Sur your upgrade could fail if it matches a very particular condition. I’ll start with a quick summary of the macOS stuck progress bar situation. UPDATE! This issue is fixed in both the Monterey 12.1 and Big Sur 11.6.2 Full installer. In certain situations, the upgrade will fail and then get stuck with a neverending progress bar.

MacOS Big Sur currently has an upgrade issue. MacOS Mojave or Catalina to Big Sur Upgrade Progress Bar Stuck Fix.

Update macos sierra to big sur