Mojave on mid 2012 Macbook pro

You are trying to install an update for macOS Mojave while being on macOS High Sierra.

These updates rom Apple Support Downloads cannot only be installed on a mac that is

running an earlier version of macOS Mojave.

To upgrade from macOS High Sierra to macOS Mojave you need to download the full installer app for macOS Mojave

which can only be done through the App Store. Your mac can also upgrade to macOS Catalina 10.15.7.

Follow these instructions.

Open Safari and click on this link, 

How to get old versions of macOS – Apple Support

Go to the Download OS section and click on the OS you want to install.

Before upgrading make a full back up of your Mac.

Check that third party apps you use have updates available for the new OS.

https://roaringapps.com

Check that your printers/ scanners etc have updated drivers and software available for the new OS.

Connect your mac to your router via cable rather than rely on WiFi.

Do not use your mac while it is downloading

and do not use any other devices that share the same internet connection.

If the App Store says ‘Open’ then it is detecting a previous download of the install app

go to the Applications folder locate Install macOS ******.app.

Move it to the Trash, empty the Trash.

Restart, click on the link again, the App Store should say ‘Get' or 'Download'.

If you are considering upgrading to Catalina be warned it does not support 32bit apps.

Your Mac is probably running 32bit apps and these will need to be updated to 64bit apps,

some updates may be free, some may be paid. Use this free app to discover which apps you have

are 32bit, https://www.stclairsoft.com/Go64/ then contact the developers of the software to see

if they are offering 64bit updates.

Yes there you go your High Sierra install is on the older Mac OS Extended (Journaled) file system.

Mojave will only install on APFS formatted disks.

Make a full back up of your mac.

Restart your mac while pressing the Command and R keys.

From the Utilities panel select Disk Utility.

Click on Edit and from the submenu select APFS if it is available.

If this is successful restart normally and then try download ing Mojave again.

Yes it should be able to run Mojave. What version is installed right now ??

The Age of this computer will Govern what newer version of macOS it will Qualify to install. Use About this Mac from the Apple Icon on Desktop - the required Information will be there.

With the above information in-hand - follow this How to get old versions of macOS and verify what version this computer Qualifies to install.  For Best results use Safari to commence the download as Others may not work.

Make Time Machine Backup  is very useful and can be used to Revert to Previous Working macOS

Notation - Mojave is the Last version to support 32 bit applications / extensions and Drivers. Catalina & Big Sur supports only 64 bit and there is no workaround.

Suggest using Go64 to find 32 bit application before attempting the upGrade. Some or many of the Application already installed may required update or upGrades to 64 Bit Versions.

Are there any AntiVirus, Disk Cleaner, Optimizers, Un-installers, etc installed which should be removed as per Developers Instructions. They are useless, unneeded, cause havoc and interfere with the normal operation of the OS and may even Corrupt the OS requiring a Reinstallation

14.7 MB is the wrong size...

macOS Mojave 10.14.6 - Technical Specifications

General Requirements

OS X 10.8 or later

2GB of memory

12.5GB of available storage (OS X El Capitan 10.11.5 or later)*

Some features require an Apple ID; terms apply.

Some features require a compatible Internet service provider; fees may apply.

Mac Hardware Requirements

For details about your Mac model, click the Apple icon at the top left of your screen and choose About This Mac. These Mac models are compatible with macOS Mojave:

MacBook (Early 2015 or newer)

MacBook Air (Mid 2012 or newer)

MacBook Pro (Mid 2012 or newer)

Mac mini (Late 2012 or newer)

iMac (Late 2012 or newer)

iMac Pro (2017)

Mac Pro (Late 2013; Mid 2010 and Mid 2012 models with recommended Metal-capable graphics cards)

Don't use FireFox for these links…

https://itunes.apple.com/us/app/macos-mojave/id1398502828?mt=12

If you get a corrupted message...

Naw, not damaged, it's just that you have an old copy already in Applications, there are 2 cures...

Disconnect from the Internet & set the Date back to 2014, then you can run the Install MacsOS Mohave App in Applications, so expired Certificates are not expired.

Or... trash the Install MacsOS Mojave.app in Applications, empty trash & restart, then a new copy of a more recent version can be downloaded..

That mac can certainly run macOS Mojave.

It may not be installing because your installation of macOS High Sierra

is still formatted as Mac OS Extended (Journaled) and Mojave needs to

be installed on a drive that is formatted as APFS.

Can you do this for us, highlight the icon of your hard drive on the Desktop

and then press Command- i.

The info panel will pop up, can you share a screenshot of it please.

The Link https://support.apple.com/en-us/HT211683 is the Only Way one is going to get the FULL INSTALLER of Mojave. Downloading an update for Mojave is predicated on Mojave Already being installed - which it is not.

Perhaps, at the Apple logo at top left, choose About this Mac, what year does that say?

Judging from last posting by OP - you are right. Drive formatted as HFS Journaled . Needs conversion to APFS - out of my abilities

Yeah you are probably right about that.

I just wonder if it has something to do with the fact that Apple last year changed the

Mojave download page from the usual 6.2GB download to this new 14.7MB pre installer download

which once downloaded and opened will then go ahead and download the full installer app.

(Oh Apple what load of nonsense you get up to sometimes.)

And wonder if that pre installer download checks the macs validity for the install.

First thing before even attempting anything - do A Time Machine Backup right away.

Personally, have not attempted this nor had the need to convert. Proceed with extreme caution.

If in doubt do not proceed

If you upgrade to macOS High Sierra with HFS but later decided to turn to APFS, then you can do the same through Recovery Mode. Restart your Mac and press-hold Command + R to boot into recovery mode. Then, go to Disk Utility << click Edit << click Convert to APFS.

Note: The above processes are non-destructive forms of APFS conversion on your chosen drive which means no data will be lost in converting the drive to APFS from HFS.

Seems like you are trying to update. which is different to an OS upgrade.

Follow link provided from P. Phillips.

Yup was still on this one. May bad and thank you.

Though, would not the download still occur and once the attempt to install to HFS / GUID alert that it can not be installed ?? Genuine question - nothing smart a**ed

When you try to install macO Mojave what happens.