MacBook Pro 2018: Downgrade Mojave back to High Sierra

[Dovahkiing]

There is no internet recovery on T2-equipped Macs (iMac Pro, 2018 MBP). You have to use another Mac with configurator installed to restore the machine if the recovery partition is messed up. I know, huge pain in the ass. I always loved Internet Recovery.

This is not true.

I have a 2018 MBP, but the Mojave beta on it and subsequently downgraded back to HS for application compatibility reasons. The downgrade was, for me, very simple. I booted into Mojave recovery partition, used Disk Utility to erase the internal drive, then rebooted (with no OS installed). Booting to recover in this circumstance brought me to internet recovery where I was able to install HS as per normal process.

 

[macnewbie2018]

Had a bit of a nightmare downgrading, so I thought I'd share my apparent success story.

After wiping the partition with Mojave on it, I made the mistake of not cold starting while holding command R. This caused the machine to show the circle with a line in it and boot into windows 10 on the bootcamp partition. I didn't realize (if this is the usual behavior) that the key sequences don't always work on a reboot versus a restart. I kept rebooting holding down key sequences and none of them worked.

Once I started from power off (using the fingerprint button on the touch bar to power down and power up) holding command R the machine went to the spinning globe screen. From there it went into macOS recovery and I reinstalled High Sierra on the empty MacOS partition. All went well. After logging in to High Sierra still had to download the recent upgrade for MBP2018. That upgrade also went fine. Now running 10.13.6 build 17g2208.

 

[MewQuest]

I'm trying to downgrade from Mojave back to High Sierra, which is now seemingly impossible. I used my iMac to download High Sierra from the Mac App Store and created a bootable external hard drive to try and reinstall High Sierra. I tried booting from the external HD to begin the install and I get a circle with a cross in it (almost like a stop sign). I've tried the recovery tool and the MacBook Pro ends up just looping thru the recovery process but never installs High Sierra. The only thing I can manage to do is reinstall Mojave. Would it be possible for me to create a time machine backup of my iMac (which is running High Sierra) and launch the recovery tool on my MacBook Pro and restore from the time machine backup? Any suggestions?

Skimmed through the replies so if what I ask has already been answered my bad.

Have you try creating and using a bootable usb containing High Sierra 10.13.6?

You can use any USB-A to C Adapter to use a regular flash drive or you could buy a USB Type C flash drive.


--EDIT: Read Preceding Post--

Had a bit of a nightmare downgrading, so I thought I'd share my apparent success story.

After wiping the partition with Mojave on it, I made the mistake of not cold starting while holding command R. This caused the machine to show the circle with a line in it and boot into windows 10 on the bootcamp partition. I didn't realize (if this is the usual behavior) that the key sequences don't always work on a reboot versus a restart. I kept rebooting holding down key sequences and none of them worked.

Once I started from power off (using the fingerprint button on the touch bar to power down and power up) holding command R the machine went to the spinning globe screen. From there it went into macOS recovery and I reinstalled High Sierra on the empty MacOS partition. All went well. After logging in to High Sierra still had to download the recent upgrade for MBP2018. That upgrade also went fine. Now running 10.13.6 build 17g2208.

Nice sounds good.

 

[geolee11]

I'm also having issues downgrading. Here's what I've attempted to do.

Downgrade using bootable USB created from build 17G2112. Result: Trying to boot the USB ends up returning me to Mojave Recovery instead of High Sierra Recovery. I've disabled the T2 security in recovery to allow booting from external media.

Downgrade using Internet Recovery using both Methods 2 and 3. Result: High Sierra tries to install but the installation either crashes or finishes but reboots back into Internet Recovery because it did not complete the install process. I've attempted this multiple times.

The only thing I can do with Internet Recovery is restore to a Time Machine backup of my Mojave beta. I would like to downgrade because external displays are not working (despite SMC and PRAM/NVRAM resets) and the brightness slider isn't working. For now, my workaround is to install Windows 10 to a BootCamp partition and wait until the next beta is released.

 

[upandown]

There is no internet recovery on T2-equipped Macs (iMac Pro, 2018 MBP). You have to use another Mac with configurator installed to restore the machine if the recovery partition is messed up. I know, huge pain in the ass. I always loved Internet Recovery.

Not true. I personally used internet recovery to clean install HS 10.13.16 on my 2018 13.

 

[randolorian]

This worked for me:

1. Install Mojave
2. Reboot into Internet Recovery
3. Use Disk Utility to wipe disk. Exit app.
4. Run Install High Sierra app

 

[geolee11]

This worked for me:

1. Install Mojave
2. Reboot into Internet Recovery
3. Use Disk Utility to wipe disk. Exit app.
4. Run Install High Sierra app

For step 1, was that a clean install of Mojave with data wiped? I may try that but I’ve repeated these steps so many times that I’m tired of having to restore my Time Machine backup after failed High Sierra installation.

 

[CNMiles]

This worked for me:

1. Install Mojave
2. Reboot into Internet Recovery
3. Use Disk Utility to wipe disk. Exit app.
4. Run Install High Sierra app

There's a step missing here between steps 3 & 4. Once you Exit the Disk Utility App in Internet Recovery Mode, then what? How do you get to step 4? Do you restart on another partition? Where are you running the Install High Sierra App from? I'm stumped.

I tried running it from my Mojave partition, but just keep getting the message that the macOS version is too old.

Help!

 

[CoastalOR]

There's a step missing here between steps 3 & 4. Once you Exit the Disk Utility App in Internet Recovery Mode, then what? How do you get to step 4? Do you restart on another partition? Where are you running the Install High Sierra App from? I'm stumped.

I tried running it from my Mojave partition, but just keep getting the message that the macOS version is too old.
Help!

While in internet recovery exit Disk Utility which should bring you back to the internet recovery macOS Utilities screen. Then select "Reinstall macOS". Since the MBP shipped with High Sierra it should install 10.13.6 for you.
https://support.apple.com/en-us/HT201314

 

[AlexCruzAmsterdam]

IF you want to buy or already bought a MacBook Pro 2018 with Mojave installed on it and want to go back to High Sierra, this is the way to do it:

1. Power on Mac, set it up and create an Admin user account
2. Download High Sierra here (step 4): https://support.apple.com/en-us/HT208969
3. Now High Sierra is installed on your current HD
4. Create external boot media on the Mojave computer (it only works on a computer with Mojave installed). This is how to create the external boot disk: https://support.apple.com/en-us/HT201372
5. Leave your external USB drive in your Macbook
6. Reboot your system and hold Command + R. Utilities Menu --> Startup Security Utility
7. Choose No Security and Allow booting from external media. Quit Startup Security Utility
8. Go to Disk Utility and delete Macintosh HD. Quit Disk Utility.
9. Shut down your MacBook
10. Press start again and hold the ‘option’ key immediately
11. DON’T use your wifi network but press ‘Install High Sierra’, if that doesn’t come up restart the computer, follow step 9 and 10 again
12. Go to Reinstall MacOS. Install High Sierra.
13. Ready

 

[Hobsie]

IF you want to buy or already bought a MacBook Pro 2018 with Mojave installed on it and want to go back to High Sierra, this is the way to do it:

1. Power on Mac, set it up and create an Admin user account
2. Download High Sierra here (step 4): https://support.apple.com/en-us/HT208969
3. Now High Sierra is installed on your current HD
4. Create external boot media on the Mojave computer (it only works on a computer with Mojave installed). This is how to create the external boot disk: https://support.apple.com/en-us/HT201372
5. Leave your external USB drive in your Macbook
6. Reboot your system and hold Command + R. Utilities Menu --> Startup Security Utility
7. Choose No Security and Allow booting from external media. Quit Startup Security Utility
8. Go to Disk Utility and delete Macintosh HD. Quit Disk Utility.
9. Shut down your MacBook
10. Press start again and hold the ‘option’ key immediately
11. DON’T use your wifi network but press ‘Install High Sierra’, if that doesn’t come up restart the computer, follow step 9 and 10 again
12. Go to Reinstall MacOS. Install High Sierra.
13. Ready

Followed these steps and now I'm stuck at internet recovery (with the spinning globe) no matter what I do. Pressing on "install high sierra" just takes me straight to internet recovery. The T2 security settings were disabled before I wiped the hard rive but I can't get back to those utilities anymore either

 

[Hobsie]

Followed these steps and now I'm stuck at internet recovery (with the spinning globe) no matter what I do. Pressing on "install high sierra" just takes me straight to internet recovery. The T2 security settings were disabled before I wiped the hard rive but I can't get back to those utilities anymore either

In case anyone gets stuck in the spinning globe cycle as I did - I was able to get out of it by creating a Mojave USB installer the same way I had made my High Sierra one. For whatever reason that works fine but the High Sierra one doesn't (and I can confirm there's no inherent issue with the High Sierra USB installer as I just now used it on an older MacBook Pro after it failed to work on the 2018 model)

 

[BigBoy2018]

Yeah.

So you looked at... bigger trackpad, super high bandwidth next gen ports, better display, better sound, better graphics, way faster ssd, faster cpu, hardware hevc which would be standard for next decade, an overall better industrial build - all of that. And decided to go with an older product.

And you justify your decision by making a point that it has an OS re-install method (internet recovery)? Don't know mate. If you got a good deal with price good for you, otherwise meh!

Good luck with that ‘super fast’ laptop when it thermally throttles, or the keyboard breaks.
Or the connection to the screen starts to fail.

 

[Sovon Halder]

Good luck with that ‘super fast’ laptop when it thermally throttles, or the keyboard breaks.
Or the connection to the screen starts to fail.

Good luck living.

 

[BigBoy2018]

Good luck living.

what does that even mean? lol

P.S. Rumor has it, as you probably are aware, tbat Apple will be introducing a redesigned laptop this year in part to fix some of the glaring flaws of the current models.
In other words a laptop that can (hopefully) leverage its capabilities without throttling, or the keyboard becoming non functional. Only then will I consider buying another apple laptop.

 

[davegoody]

This does not seem to be the case. Just as OP mentioned, the internet recovery option just keeps looping through the install process over and over.

I'm experiencing the exact same issue trying to go back to High Sierra.

It may be the Disk format that's the problem here (apologies if that has already been suggested). HS uses HFS+, Mojave uses HPFS, format the drive in the correct format first.

 

[medeiom1]

Unfortunately, whatever macOS comes with your new Mac, you cannot go to a previous macOS. You can however go back to your original macOS when future macOS are released.

 

[Riwam]

Unfortunately, whatever macOS comes with your new Mac, you cannot go to a previous macOS. You can however go back to your original macOS when future macOS are released.

Would you mind explaining it.
Thanks.

 

[BigBoy2018]

Unfortunately, whatever macOS comes with your new Mac, you cannot go to a previous macOS. You can however go back to your original macOS when future macOS are released.

There is a fine point to make here.

Right now, for instance, if you buy a current model iMac (which was released in June 2017) it will come with Mojave installed. However, all 2017 iMacs orginally came with Sierra 10.12.5 installed .
As a result, you can still downgrade those models to Sierra (or any iteration of mac os between 10.12.5 and the current release) if you want.

>Even though they are currently shipping with 10.14.3 Mojave<

Bottom line, regardless what os is installed when you buy it, your mac can run as old an os as the one that came with it when that model was FIRST released.

 

[medeiom1]

Would you mind explaining it.
Thanks.

I tried so many different methods including cloning a high sierra MacBook to the latest 2019 MacBook and I ended up with a prohibitory symbol. It turns out the latest second generation T2 security chip, prevents downgrading on new MacBook pros. If anyone successfully downgraded, I am all ears!

 

[BigBoy2018]

I tried so many different methods including cloning a high sierra MacBook to the latest 2019 MacBook and I ended up with a prohibitory symbol. It turns out the latest second generation T2 security chip, prevents downgrading on new MacBook pros. If anyone successfully downgraded, I am all ears!

Have you tried creating a 10.13.6 high sierra install usb stick and reformatting and then doing a clean install?

If this is true, that the T2 chip prevents downgrading the OS after you’ve upgraded to a newer OS then thats a seriously f-ed up move by Apple. I frequently put the orginal os that comes with my mac on a spare partition just in case I run into compatability issues with whatever the latest OS is.

 

[medeiom1]

That was my first method with a good USB bootable of HS and no go.. prohibitory symbol. I tried target disk mode from another High Sierra machine, deleted and recreated the volume UUID but failed.

Lastly, I did get a confirmation from a former Apple engineer who agreed on my assessment on the second generation T2 security check. WYSIWYG... What you see is what you get and there’s no going backwards.

 

[BigBoy2018]

That was my first method with a good USB bootable of HS and no go.. prohibitory symbol. I tried target disk mode from another High Sierra machine, deleted and recreated the volume UUID but failed.

Lastly, I did get a confirmation from a former Apple engineer who agreed on my assessment on the second generation T2 security check. WYSIWYG... What you see is what you get and there’s no going backwards.

You can turn off secure boot. Have you done that as well?

 

[medeiom1]

Not to toot my horn here but I am a Mac technician and all T2 security features have been turned off. Bottom line, Apple does not want anyone reverting back to previous macOS on new Macs.

 

[BigBoy2018]

Not to toot my horn here but I am a Mac technician and all T2 security features have been turned off. Bottom line, Apple does not want anyone reverting back to previous macOS on new Macs.

If true, I am stunned. I may start a new thread asking for confirmation on this. Not that I think you’re wrong, but maybe its something wrong with your soecific system?
I’m grasping at straws here, but I am thoroughly aghast if this turns out to be true