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I really need to run macOS High Sierra 10.13 as my primary OS natively (not via virtualisation etc).

Is it possible to downgrade a 2018 MacBookPro using a USB installer to macOS High Sierra 10.13 ?

Would it have the required drivers etc?

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2018 MacBook Pro originally shipped with macOS High Sierra 10.13.6.

It is possible to downgrade it to run the said release of macOS High Sierra on your MacBook Pro.

You can install macOS High Sierra 10.13.6 by downloading it from the Mac App Store, creating, booting and installing it via a USB installer. Alternatively, you can also use Internet recovery to directly download and install it natively.

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High Sierra can be downloaded from Mojave by selecting Get macOS High Sierra on the Apple website How to upgrade to macOS High Sierra. High Sierra appears in the App Store as shown in the image below.

enter image description here

The download will appear as a software update, as shown in the image below.

When finished downloading, you will get the popup message shown below.

The installer will appear in the Applications folder, as shown in image below.

The instructions for creating the USB installer can be found at the Apple website How to create a bootable installer for macOS. Basically, there are two steps:

  1. Use the Disk Utility application to erase the flash drive. Choose the following options.

  2. Enter the following command in a Terminal application window.

    sudo /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume
    

    Once step 2 completes, you can boot from the USB installer by restarting the Mac and immediately hold down the option key until the Startup Manager icons appear. The USB installer will appear as one of the choices to boot from.

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    You cannot install an older macOS that came with your machine. Verify what was initially installed on the machine. I use mactracker.app – historystamp Apr 12 at 19:31
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    @historystamp: I did verify that all 2018 MacBook Pro models originally came preinstalled with macOS 10.13.6. So, I do not understand your comment. Could you clarify? – David Anderson Apr 12 at 20:30
  • I should have added the note to the original post. Sorry about that. – historystamp Apr 12 at 22:42
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Apple documents the things to check if you ever manage to install or bring an older OS to newer hardware where driver support isn’t complete or even available:

If you don’t have a record of the OS that shipped, you can make a backup, erase the hard drive and then use Internet Recovery to ask for the proper version that shipped with your serial number. Apple does ship newer hardware within the same marketing name from time to time, so contact Apple Support if you need to know the version of the OS that shipped with a specific serial number.

Hold Shift-Option-⌘-R to get the original version (or the closest newer version past what was original if the original is no longer available from Apple content delivery network that powers Internet Recovery.

This is not a downgrade, you erase everything and walk away from an easy migration of a newer backup to a clean installation of an older OS. Many files and apps work well by manually migrating, but the official tool will want to force you to upgrade to the version that made the backup if you ask it to migrate data to an older OS build or version.

  • You make the assumption that the operating system put on the Mac when it is made is the same operating system you get when you remove the new Mac from the box. This is not always true. – David Anderson Apr 13 at 16:31
  • @DavidAnderson I don’t intend to convey that assumption. I hoped to say Apple records the factory version - not that you receive the factory version. In 99.9% or higher cases, this should be irrelevant in practice. Should an edit be made to clarify? – bmike Apr 13 at 16:56
  • My complaint is not with the answer you posted, but rather the content of the first link in your answer. This site gives the impression that version of MacOS that comes with a Mac is the earliest that the Mac was designed to use. This is not necessarily true. In this case, this model Mac was introduced July 12, 2018 with High Sierra 10.13.6 installed. Mojave was not released until Sept. 24, 2018. Yet, if you purchased this model today from a authorized Apple dealer, you should expect Mojave installed. So, at some point, the 2018 MacBook Pros shipped with High Sierra were upgraded to Mojave. – David Anderson Apr 13 at 18:31
  • Got it - Apple didn’t do the job you wanted in the KB. Thanks @DavidAnderson - I was open to changing my post if it could help others. In the old days, we would go in and update, then we would go in and slip in a DVD, then we just let it be outdated. I don’t know of any vendor that updates “new” Macs. I used shipped in my answer - perhaps saying “made” would be more precise than “shipped” – bmike Apr 13 at 18:42

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