macOS 10.15 & 32-bit Apps

For the first time in over about 30 years of owning Apple computer products I DREAD this fall when the Mavericks successor (macOS 10.15?) is released.

I have upgraded from pre OS X through macOS 10.14 and my (yes sluggish) iMac is facing a big change in life (and yes I still, yesterday, used iWeb to update a web site)

A few questions, does anyone have information or informed speculation:

  1. I have MANY 32 bit applicaiotns. Many still used that I haven’t found an update for OR a replacement. Will an UPGRADE to 10.15 remove all the 32 bit files (Apps and associated data / preference) files? Or will they all be put into a folder I can delete? Or will they be trying to run in the background and create even more sluggishness?
    My sense is the answer to the above is NO!

  2. I haven’t done a clean install of a new operating ever. The task seems daunting. I know I will have to do that when I upgrade to 10.15
    Are there prior TidBITS messages OR Take Control books to use for reference?
    I only have one computer but both Clone and TM hard drives. It seems it might be possible but challenging

10.15 is, to me, much more scary than the loss of Rosetta


I certainly don’t believe that any of the data / preference files associated with a 32-bit file will be either removed or moved to a separate folder. We will all need to wait until at least WWDC-19, if not later to learn what will actually happen. My suspicions are that you will simply see a “cannot open” icon on any 32-bit apps you have and 64-bit apps that still have 32-bit processes associated with them will simply not work, either completely or partially. There should not be any sluggish background processes, only crashes or no action at all.

Although a clean install once in a while is normally a good idea, i don’t think it will be required for 10.15, but again we don’t have any real information yet on which to base recommendations.

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You could make a clone before you migrate. Then after migration throw away all apps that cease to work with the new macOS. Instead, create a VM based on your orignal clone. That’s where you go to use old apps. Doc exchange through common folders should be trivial.

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Information about this on Apples support site, also how to find out if your apps are 64 bit. If your app developers don’t update their apps to 64 bit, they will stop working at some future update, which is all this support article says.

Much to my chagrin, we have a number of supported machines which will continue to run versions from El Capitan through High Sierra and even Mojave – and a couple instances of Snow Leopard (Server) – in a VM, just so access to many dated, but impossible/difficult (e.g., Quicktime 7) and bothersome (e.g., iWeb, etc.) to replace apps can continue to live past their best-by dates.

Both Fusion and Parallels make sharing data in common Shared and User folders seamless and painless, so other than needing adequate RAM for the VM and plunking down the bucks for a novice-friendly interface (I feel the open source options are just too ugly for nervous users), they are totally viable.

As stated above, you can clone your existing functioning 32/64-bit macOS installation, and drop it into a VM intact; but I would caution that environment might have a number of background apps and tasks running that would be unnecessary duplicates in a VM, so you’d want to police the Startup and Login items to make sure you’re not running things there you don’t need (e.g, Adobe, Chrome, et al, Updaters; iStat Menus, Memory Clean, etc) inside the VM.

As for clean installs, don’t let the myths lead you down a painful path; it’s *NIX, not Windows; it will only load what you (and your app’s installers) tell it to load, and nothing else; it doesn’t have a Registry filled with dead .dlls and countless conflicts when something dies.

I am literally running the same Mac OS to macOS installation started with the original release (and I believe even from the OS X Public Beta); there are zero measurable, let alone perceivable performance differences between it and a virgin installation of macOS and like applications. It has migrated across several Macs, as has most all the installations in our groups.

With rare exception, when a new Mac is acquired, we simply transfer a clone to the new Mac and keep working with little interruption. The only exception is when a new Mac ships with an as-of-yet-unreleased version of macOS specific to that hardware, which these days, is exceedingly rare.

It’s my belief that people who espouse a regular or periodical fresh installation of macOS and all your apps, and then often a manual migration of data (i.e., not even trusting Migration Assistant), are often coming from the Windows World, where this practice absolutely is beneficial and frequently necessary; that they are perhaps reflecting on days when wiping an HDD and starting clean, rather than just pruning and defragging a disk would meet the same end, and has little impact on today’s SSDs; or that they have so few apps they can do this in just a few hours; or they are natural born tinkerers, who gain great satisfaction working on their computers, rather than with them.

The only thing you might need to be afraid of with your aging Mac is a lack of adequate RAM; I try to push anyone who does anything that pushes RAM (Safari, Photos, Fantastical 2, etc.) or likes to have multiple apps open at once, to run at a bare minimum 8GB starting with macOS Sierra, and preferably 12GB-16GB is you’re going to also run a VM and expect to use both environments simultaneously. You can do it with less, but even with an SSD, it will be horribly, horribly slow.

Hopefully your iMac already has enough RAM and a good SSD; if not, look to invest there before you worry about moving to Mojave and beyond; if your Mac is too old for those upgrades, either stay put and don’t worry about the latest macOS, or find the money for a new or new-enough used Mac.

Even if you can find replacements for all your current 32 bit apps, the money is likely better spent on hardware upgrades and running your preferred/current apps in a VM. Or not. You’ll have to do that math.

Quoted for emphasis.

I’m running essentially the same install I have been running since OS X Public Beta. I’m pretty sure my HS install is cleaner and better performing than most other installs you’ll find, including those of people who follow the Windows mantra of nuke, install from scratch, and then spend days (to months) migrating stuff back.

Thank you Frederico and Simon

Two thoughtful comments. I will think harder about doing (or not doing) a clean install.
My 16 month old iMac is sluggish (not SSD ) but maybe there are other reasons


If you are running Mojave on a computer with a mechanical hard drive it will be sluggish because the drive has been reformatted to APFS which is awful on mechanical drives. I would have the hard drive replaced with an SSD. Apple won’t do it but most AASP’s will do it for a very reasonable price.

Thanks I didn’t know that Mojave would have changed my internal mechanical hard drive. Sure wasted $$ by buying the 1 TB hard drive model


I am an Apple Consultant and have had to deal with a few of these. I use a local AASP and they replace the mechanical drive with an appropriate sized SSD. I have done a few 21.5" iMacs that way. A 27" costs a bit more because they need to install a thermal sensor and an adaptor for the 2.5" SSD but it is still reasonable to do.

The biggest issue is digging through the Launchd items and such and making sure some ancient printer driver isn’t loading up a “check ink levels and remind them to buy more” or similar nonsense.

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Howard Oakley has created two utilities that will help you figure out what’s 32-bit and what’s not:


… or refuse to “upgrade” to 10.15 so that you can continue to use legacy apps that do the job better than more modern apps (if any are actually available).

In my view the withdrawal of support for 32 bit apps is very short-sighted. It is laughable that an organisation with the resources of Apple could not provide support for 32 bit without noticeably affecting 64 bit performance. I would not be surprised if, following the WWDC, some class actions get underway on this issue.

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That would be a big waste of time, effort and money, IMHO.

Can someone explain to a novice in this area why I can’t ensure I know what apps I’m using are 32 bit (About this Mac, System Report and Applications) and check with the developer to see if they will be going to 64 bit - and if not, find a replacement if needed?

Appreciate the help/advice.


Al Varnell

    May 29

I would not be surprised if, following the WWDC, some class actions get underway on this issue.

That would be a big waste of time, effort and money, IMHO.

Assuming you are currently running High Sierra 10.13.4 or above, the easiest thing to do is to watch for the notification the first time you launch it that “App” is not optimized for your Mac and needs to be updated, as explained in 32-bit app compatibility with macOS High Sierra 10.13.4 and later.

For apps that have already been opened at least once before hold the option-key down, click on the  menu and select Software Information… then look under Software->Legacy Software for a list of those.

Neither of those methods will find each and every 32-bit process on your Mac, but it’s a good start. The most thorough way that I’ve found of locating everything is to use one or both of the utilities Adam proposed earlier: 32-bitCheck & ArchiChect.

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Apple has gone through this sort of transition several times already, first with the move from the classic Mac OS to Mac OS X, and then again with the Rosetta environment that enabled PowerPC applications to run on Intel-based Macs. Each time, the company has telegraphed what was coming years in advance, provided a long transition time, and taken a lot of flak when it finally pulled the plug (in Tiger for Classic and in Snow Leopard for Rosetta).

One aspect of the problem that many people don’t think about is that supporting potentially obsolete software creates a nightmare for testers because the test matrix becomes significantly larger.

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Would this also apply to a 2017 27" iMac with a fusion drive?

Yes. All storage formats are APFS. Fusion performance is adequate based on my own experience. Heavy I/O may be the exception.

Frederico – it sounded simple in your post but … I am trying to install Snow Leopard (10.6) into Fusion but am having no luck. Even added the suggested code line to the vmx file (because I have an i5 processor) and still no joy. I have both install disks (10.6.4) and a disk image of my SL system (10.6.8) that I keep on an external drive. I do not have a server version however. I am new to Fusion, so that may be the problem, too. My last option is to install Fusion on my very old MacBook running El Cap. Can I try that and then add SL there, and later transfer to my new iMac? Suggestions? Thanks!