How do I reinstall macOS X that won't boot?

When your Mac won’t boot properly into macOS, reinstalling the operating system is often the best way to get it up and running again. However, this can be tricky if macOS itself is having issues. Here are some steps to try reinstalling macOS when your Mac won’t boot correctly.

Table of Contents

Requirements

Before starting, make sure you have the following:

A Mac computer that won’t boot properly

An external hard drive or USB flash drive with at least 12GB of available storage
A working internet connection
Access to another functional Mac to create a bootable installer

The latest macOS installer from the App Store (or a local copy on another Mac)
Patience and time to troubleshoot if necessary

Step 1: Create a Bootable macOS Installer

The first step is to create a bootable macOS installer on an external drive. This will allow you to boot and install macOS on your non-working Mac.

To create the installer:

Format your external drive (USB stick or hard drive) and give it the name “Untitled”
On a working Mac, download the macOS installer if you don’t already have it

Open the Terminal app and use the createinstallmedia command to make your external drive bootable
Wait for the installer to finish making your external drive bootable

For detailed steps, follow Apple’s support guide on creating a bootable installer drive.

Step 2: Start Up From the Installer Drive

Next, you’ll need to start up your non-working Mac from the installer drive:

Connect the bootable installer drive to your Mac
Turn on your Mac and immediately press and hold the Option key

Select the external installer drive on the Startup Manager screen
Your Mac will boot from the installer drive into macOS Recovery mode

If your Mac is not turning on or not responding to the Option key method, you may need to reset NVRAM and SMC to get it to recognize the bootable installer drive.

Step 3: Erase the Internal Drive

With your Mac booted from the installer drive into Recovery mode, you can erase the internal drive:

Go to Utilities > Disk Utility
Select your internal hard drive in the sidebar

Click Erase at the top
Give the drive a name and select Mac OS Extended format
Click Erase to wipe the drive

This will erase the existing files and partitions on the internal drive and prepare it for a fresh install.

Step 4: Reinstall macOS

With your drive erased, you can now reinstall macOS:

Quit Disk Utility and go back to the macOS Recovery menu

Select Reinstall macOS and click Continue
Follow the onscreen prompts to install the latest macOS
The installation will take some time to finish

Your Mac will reboot a couple times during the installation process. When it’s done, you should see the macOS setup assistant and can configure your new system.

Troubleshooting Tips

Here are some troubleshooting tips if you run into issues during the reinstallation process:

If your Mac won’t start up from the installer drive, reset NVRAM and SMC first

If the installer still won’t boot, try using a different USB port or external drive
If Disk Utility won’t erase your internal drive, run First Aid to check for errors first
Check your internet connection if the installer gets stuck downloading files

If there are still issues after reinstalling macOS, your hard drive may need replacing

Frequently Asked Questions

Why won’t my Mac turn on at all?

If your Mac won’t power on, even after resetting NVRAM and SMC, there could be an issue with the power supply, logic board, or other internal components. You may need to get it serviced by Apple or an authorized repair center.

How can I find my data after reinstalling macOS?

Reinstalling macOS erases all data on the internal drive. However, your files may still be recoverable using data recovery software. Or, if you had a backup, you can restore files from your Time Machine or other backup after reinstalling.

Do I need internet to reinstall macOS?

An internet connection is required to redownload the full macOS installer during the reinstall process. If you don’t have a working internet connection, you’ll need to use a local copy of the installer on a bootable drive.

Can I reinstall an older version of macOS?

Yes, you can install an older version of macOS using a bootable installer drive created from the installer for that OS version. However, Apple does not recommend downgrading and some older versions may no longer get important security updates.

Will reinstalling delete my recovery partition?

The recovery partition is typically deleted and recreated during a macOS reinstallation. This allows your Mac to reboot into recovery mode after the reinstall is complete.

Summary

Reinstalling macOS is an effective way to revive a Mac that won’t boot properly. The key steps are:

Create a bootable macOS installer drive
Boot your Mac from the installer drive

Erase the internal drive in Recovery mode
Reinstall the latest macOS system

Be sure to try resetting NVRAM and SMC first if your Mac won’t boot. Have patience and be prepared to troubleshoot. Back up any needed data first, as the process will erase your drive. With some time and care, reinstalling macOS can get your unresponsive Mac up and running again.

Conclusion

Reinstalling macOS is often an effective solution when your Mac is having critical startup and system issues. While it can take some time and technical steps to complete, the process allows you to wipe your drive and start fresh with the latest macOS version. With a bootable installer drive, recovery mode utilities, and patience for troubleshooting, you can get your Mac back in working order. Just be sure to backup any important data first, as reinstalling macOS will erase your drive. With these steps, you’ll be back up and running on your Mac in no time.

Step	Description
1	Create Bootable Installer Drive
2	Boot to Installer Drive
3	Erase Internal Drive
4	Reinstall macOS

Related Resources

For more help with reinstalling macOS, check out these Apple support articles:

How to reinstall macOS from macOS Recovery

You can also find helpful tutorials and guides from third-party sites:

With the steps outlined here and some help from online resources, you should be able to successfully reinstall macOS and get your Mac running like new again.

How do I reinstall macOS X that won’t boot?