Fix Mac not booting after macOS update (The Definite Guide)

By Vivian | Posted to Mac Data Recovery, updated on June 28th, 2020 |

Summary: This post is about how to fix when Mac won't boot after macOS update. If macOS Big Sur or macOS Catalina update makes your Mac not booting up, you'll know why and how to fix it quickly and easily.

Table of contents
1. Why is your Mac not turning on after macOS update?
2. Common boot problems after macOS update
3. What to do if Mac can't turn on after macOS update?
4. How to recover lost data when Mac is not booting after macOS update?
5. How to avoid macOS update failure?

mac wont boot after macOS update

Apple releases macOS and software updates periodically for better user experience. However, it backfires when your Mac won't boot after macOS update. Especially for some Mac newbies, Mac not turning on would drive them crazy.

Hence, this post will walk you through this problem. Then, you'll know what to do when Mac gets stuck on the Apple logo.

All right. Let's begin with why your Mac is not booting up after the macOS update.

Why is the Mac not turning on after macOS update?

Why won't Mac update successfully? It's fair enough to say, most of the time, Mac won't turn on after macOS update because of software incompatibility and bugs.

As we all know, technology inspires new programs and hardware to be released constantly. So, your Mac needs to update to work with most software and hardware. Sometimes, it's an overall macOS update. And sometimes, it's a tiny patch like this.

Mac update is available

In detail, a macOS update could involve those activities.

  • Upgrade certain necessary drivers. Sometimes, it simply installs patches to fix bugs. But sometimes, it will replace the whole driver structure to better use hard drives, keyboard, mouse, microphone, camera, etc.
  • Upgrade the Kernel programs. Such updates will improve the security, accessibility, and management of core data.
  • Redesign or update certain built-in applications. Utilities like Disk Utility, Safari, and Mail come along with the operating system. So, it could be updated for a better user experience.
  • Other updates like operating system structure, file system, user interface, etc.

These updates are usually for a better user experience. Or they are for better supporting most of the latest hardware and software. However, as it is pointed out, the updated macOS can only work "most" of them.

For example, Nvidia GTX 750 Ti can't work with Mac OS X earlier than Yosemite. After such a software update, Mac is not worknig, or the Mac or MacBook gets stuck on a loading bar after update. Once the third-party software and hardware on your Mac won't work with the latest macOS, your Mac won't turn on.

Common boot problems after macOS update

macOS is an improved range of Mac operating systems after Mac OS X. Up to now, there are three macOS systems available: macOS High Sierra, macOS Mojave, and macOS Catalina. Nevertheless, updating to each of them could cause problems.

1. Mac won't turn on after macOS Big Sur update

The newest major release of Mac operating system is macOS 11 Big Sur, which now is in beta version. Up to now, known boot issues of macOS Big Sur Beta include the following, or more.

  • If you updated to macOS Big Sur 11 beta from a previous version of macOS, Software Update might show "Unable to check for updates - Failed to download the documentation for the minor update. Please try again later".
  • You might be unable to install macOS Big Sur 11 beta onto additional volumes.

2. Mac won't boot after macOS Catalina update

Then it comes to macOS Catalina. Even though it should be better than the previous two, (In some aspects, it is.) Catalina update problems like Mac won't boot after macOS update still occur.

macOS 10.15 Catalina

Except for APFS conversion, the macOS Catalina update will automatically divide your hard drive into two volumes. One is the read-only Macintosh HD system volume, and the other is Macintosh HD - Data for saving your files. But if there is not enough free space for an update, your Mac will get stuck on a update loop.Whta's worse, you might see the Mac folder with question mark at startup because macOS Catalina update is not found.

What's more, the 'Full Disk Access' permission might be a lion in the way for some unauthorized applications. For instance, you have a program that requires certain Kernel extensions. But after updating to macOS Catalina, this program can't access the Kernel resource anymore. It doesn't have permission. As a result, your Mac will be frozen at the loading bar because this program keeps asking for resource permission.

3. Mac won't restart after macOS Mojave update

macOS 10.14 Mojave is coming after 10.13 High Sierra. Thus, the same boot problems on macOS High Sierra could also happen to macOS Mojave. As you might know, Apple introduced the System Integrity Protection (SIP) feature since OS X EI Capitan. It was originally introduced to keep system security. But once this feature was disabled previously before you update to macOS Mojave, it could cause boot problems.

macOS Mojave update is available

For example, the Google software update on September 23, 2019, was shipped with a bug. This flaw damages the macOS file system on computers where System Integrity Protection is disabled. Many video professionals reported that their Mac crashed due to this.

So, just think about it, even Google can't avoid such software conflict, how about other third-party software? That's one of the reasons why many users who disabled SIP previously get Mac crashed after installing macOS Mojave.

4. Mac won't boot after macOS High Sierra update

One of the major updates in macOS High Sierra is the introduction of the Apple File System (APFS). As a part of the upgrade process, the macOS High Sierra installer will automatically convert the SSD to the APFS file system.

APFS cause problems after macOS update

Even though Apple claims that the conversion process is supposed to be risk-free, many Mac users still meet problems. And disk corruption during the update is one of them. In this case, it's sure that the Mac won't restart after update. Mac will stop loading after update for such corruption.

Except for hard drive corruption, hardware or software incompatibility is another major reason. As your computer needs to work with so much hardware and software, the in-between conflict is inevitable. Those incompatibilities could slow your Mac down. They could make your Mac not responsive. Or, the Mac would be stuck on login screen. Also, the Mac could freeze on a black or Mac white screen of death.

What to do if Mac can't turn on after macOS update?

Having discussed why Mac won't boot after macOS update, you may find that it's tricky to hit the point. But don't worry, here are some inspirations so that you can troubleshoot this issue step by step:

  1. Check if the Mac hard drive is corrupted
  2. Check if any program is not compatible with your macOS
  3. Check for a hardware incompatibility

Step 1: Check and repair the Mac hard drive in macOS Recovery mode

If your Mac refuses to boot after the update, you should check the Mac hard drive. Chances are that your MacBook ran out of power and the APFS reformatting process was interrupted. Or the hard drive is corrupted for bad sectors.

In this case, you can try to repair the hard drive with Disk Utility under Recovery Mode. Disk Utility helps Mac boot up in some ways sicne it's the built-in free disk repair tool on your Mac.

If no disk error was found by Disk Utility, then the hard drive should not be responsible for this issue. To find out why you can't turn on your Mac after macOS update, you can try Safe Mode.

Step 2: Boot your Mac into Safe Mode

You may be wondering "why should I do this in Safe Mode?" The reason is that Safe Mode will only launch some basic necessary programs at startup. It’s easier to isolate incompatibility software that makes your Mac unbootable.

Make sense, right? Then let's dive into details on how to do this.

  1. 1. Press and hold the power button until the Mac forcibly shuts down.
  2. 2. To start the Mac up in Safe Mode, restart this Mac with Shift key pressed and held.
  3. 3. Release the key when you see the progress bar.

If you boot into Safe Mode successfully, you'll see Safe Boot at the right top. At least, it indicates that the macOS update is not failed. Then, it should be third-party software incompatibility.

boot into mac safe mode

But to figure out exactly which program makes your Mac unbootable, you need to reboot into Verbose Mode. Verbose mode allows you to see what's happening when macOS is starting up.

You can hold Command + V at startup. Then you'll see a live report when your Mac is booting up. Once you find out the culprit, you can simply uninstall the software in Safe Mode

boot into mac verbose mode

But if you fail to boot into Safe Mode, it means it's a macOS update failure. The system data is damaged or broken. You need to reinsall the macOS in macOS Recovery mode. You can simply boot into macOS Recovery Mode and choose Reinstall macOS. If you don't want to update macOS anymore, you can try your luck with using APFS snapshot to recover your system.

The point is that macOS reinstallation will risk your data on the Mac. Thus, you should first check your backups. Or you can recover data from unbootable Mac first.

Tips: You can prevent APFS conversion with start to install this time if you want to avoid unnecessary problems. But you are not advised to unless you are a Mac command geek.

Step 3: Ask Apple repair store for help

The toughest thing is that your hard drive is fine. And there is no software incompatibility noticed in Verbose Mode. In this case, you should check the hardware inside your Mac.

The reason is that macOS updates are always for better supporting the latest software and hardware. So, the hardware or drivers on your Mac may be too outdated to work with the newer OS.

In this case, you can ask help from the Apple repair store and reset the Mac. If it's the Mac machine itself is too old, you should replace it with a newer Mac model. Or you simply don't allow automatically update the macOS.

How to avoid macOS update failure?

Avoid Mac crash before macOS update

Every time there is a new macOS update available, you'll receive a notification. It asks "Do you want to restart to install these updates now or try tonight?". However, it's not safe to update directly because your Mac could get stuck on update or even lose important files. In case the Mac won’t boot after macOS Big Sur or Catalina update, you surely can do some preparations in advance.

  • Read several reviews from tech enthusiasts to learn problems when a new macOS beta is released.
  • Make sure your Mac model and its hardware work with the updated macOS.
  • Read macOS update instructions carefully when you are up to update your system.
  • Back up your files, photos, documents, etc.
  • Make sure there is enough free disk space for macOS update.
  • Make sure your Mac is connected to power to avoid the black screen of death during macOS update.

So, you'd better do these preparations before you update to any operating system. But if your Mac can't boot up already, you should calm down and follow this guide to fix this issue. If you have any more any feasible solution to enrich this article, kindly drop us a hint at [email protected]