Apple's latest version of macOS, 10.15 Catalina, is very similar to previous versions of the operating system, but differs significantly under the hood. The biggest change is that Apple pulled out all the code that was used to run older 32-bit apps on Apple's 64-bit operating system in earlier releases. Apple warned us years ago that this change is imminent, and there is no doubt that a 64-bit operating system like Catalina is more efficient than an operating system that runs both 32-bit and 64-bit code. Nevertheless, for many users, Catalina blocks apps that they have been relying on for years. Here's how to run 32-bit apps on an operating system that's not designed for them.
Before you upgrade to Catalina, you need to find out if you are using 32-bit apps that you can not without. The easiest way to do this is to click on the Apple icon in the upper left corner, then click About This Mac, then System Report, and scroll to Software / Programs. It takes a while for your Mac to gather information about your apps. It will then display a list of all apps on your computer. Locate the column titled "64-bit (Intel)" and click the column header. All of your 64-bit apps will show a yes in this column. All 32-bit apps are marked No. You may be surprised at how many 32-bit apps you have. Study this list, and if you find 32-bit applications that you need, you will need to get a 64-bit update or find replacement or you can implement the workarounds below.
The 32-Bit Applications That You Can Find on Your Computer There are usually two types of computers: older Mac apps that have been abandoned by their developers (or whose update is delayed), and apps that are on the Mac Wine software project that allows Mac and Linux computers to run Windows software. ( Wine stands for "Wine is not an emulator", but effectively emulates Windows features, so some, but not all, Windows applications can run on Mac and Linux computers.)
If required Apple may unofficially either run an old Mac on your hand that runs a pre-Catalina version of the OS or that your current Mac partition, so it too with a 32-bit application older macOS version can start as Catalina. Both methods work, but both seem to be uncomfortable and time consuming. However, there are better alternatives.
The simplest way is to buy a copy of Parallels Desktop or VMware Fusion if you do not already have one. These programs were developed primarily for running Windows on a Mac. However, you can also use it to create a virtual machine that runs macOS in a window on your Mac desktop. Parallels is the easiest to use, but VMware Fusion is not far away.
The steps differ depending on whether you are still running macOS Mojave or have already upgraded to Catalina. Let's start with the steps you need to perform if you are still performing Mojave. Each step corresponds to a screen in the slideshow. [1
1. Launch Parallels Desktop
From the File menu, choose New to open the installation wizard. In the Free Systems section, scroll to the right and click Install MacOS 10.14.6 Using the Recovery Partition. (You may see a different version number on your system.) If you have upgraded to Mojave from an earlier operating system version, you might see options for installing this earlier version. Choose the version that makes you feel most comfortable.
2. Create New Virtual Machine
The next page in the wizard is macOS 10.14.6. Click the Install button. Parallels launches the macOS installer and creates a new virtual machine. When that's done, a screen will ask you which language to use to interact with your virtual Mac. Choose your preferred language and continue.
3. Preparing the macOS Mojave Installation
The macOS recovery environment is now opened in the virtual machine. (This is the screen that each Mac displays when you press Cmd-R at startup.) On the macOS Utilities menu, click Reinstall macOS. On the next screen you can install macOS Mojave. Click on Continue. On the License Agreement screen, click Accept, and then click the Accept button on the pop-up menu.
4. Install macOS Mojave on the Virtual Hard Disk
The following screen provides the ability to install Mojave on a hard disk called Macintosh HD. This is not your Mac's hard drive, but a virtual hard disk in the Parallels virtual machine. Click Macintosh HD, and then click Next. Wait while Mojave installs on the virtual disk. This can take more than half an hour.
5. Setting up macOS Mojave
The virtual Mojave displays the same setup screens that are normally displayed when installing an operating system on the Mac.
6. Completing MacOS Mojave installation
When the installation is complete, the default Mojave desktop will be displayed. In the main menu of your current Mac (not in the top-line virtual machine menu), select Actions and then Install Parallels Tools.
7. Install Parallels Tools
Follow the instructions to install the Parallels Tools on your Mojave virtual machine and reboot the virtual machine.
8. Transfer Your 32-Bit Applications
Drag your 32-bit applications from your real Mac into the Mojave virtual system. Double click on it to execute it. If you're running Mojave and not an earlier version, the familiar pop-up warning will show that your 32-bit version is not optimized for macOS and needs to be updated. Ignore the warning.
9. Upgrading the Operating System
Now you can upgrade to Catalina. After completing the upgrade, start Parallels Desktop and your Mojave virtual machine. (In this screenshot, Mojave runs at night to display the night-time desktop image, but it is the same virtual machine shown on previous screens, in which case a 32-bit app is running, which in Catalina itself runs
10 Wrap It Up
With the 32-bit app running, go to the Parallels main menu and select View / Enter Coherence "The app will appear in a separate window on your Mac desktop, and a second main menu (the virtual Mac menu) will appear under the main menu of your main macOS installation. Catalina is running, but a 32-bit application is running in a window Like any other app window, the virtual machine dock is visible at the foot of the screen, but it's easy to disable the virtual machine's system settings n.  You can now explore the Parallels fine-tuning options for your apps and use the System Settings app in the virtual Moja. When the virtual machine starts, one or more 32-bit apps must start automatically. (Go to the Users & Groups preference pane and then the Login Items tab.)
Another Catalina option
But what if you've already upgraded to Catalina or if you have a new Mac running only Catalina and you can not install Mojave with the recovery partition of your Mac in Parallels. Everything is not lost. You must download the Mojave installer from the Mac App Store and use it to install Mojave in Parallels.
Following the release of Catalina, Apple has no option to download Mojave from the App Store, but it remains available on Apple's servers. If you're looking hard enough on the Apple website, you'll find the web address that opens the App Store page, where you can download the Mojave installer. I did the search so you do not have to. Just visit this Mojave page and the App Store offers the Mojave installer for download. If you want to download and install the previous operating system, visit the High Sierra page.
Select the cloud icon to download the installer. Your Mac will ask you if you really want to download it. Confirm this and wait for it to download to your application folder. Do not let it run! Instead, start Parallels Desktop and open the installation wizard from the File / New menu. Click the middle icon "Install Windows or another operating system from a DVD or image file". The next screen may display the MacOS Mojave installer. If this is not the case, drag the installer into the window and follow the instructions to create and use a Mojave virtual machine, as described in steps 4 through 10 above.
If you're using VMware Fusion, you'll need to use the same procedure, whether you've upgraded to Catalina or not. Launch Fusion, click New on the menu to open "Select installation method". An option to install macOS from the recovery partition appears. Do not try to use it because it will tell you that no recovery partitions were found, even though you know exactly that a recovery partition exists. I asked VMware about this error, and maybe it will be fixed in a future release.
So instead of using the recovery partition, you'll need to download a Mojave or High Sierra installer, as described above, and drag it into the installation window. Follow the instructions to install a virtual machine. When the new virtual machine starts, use the Virtual Machine / Install VMware Tools menu to install VMware Tools. After restarting the virtual machine, drag in your 32-bit apps and run them in the same way as you can run them in Parallels. VMware uses the name Unity for the same option, which Parallels calls Coherence. It runs an app in a virtual machine in a way as if the program is running in a window of your main MacOS installation.
You Can Run Weaker Apps, Too
What if you use a wine-based app to run a Windows game or a Windows app? In almost all cases, the Wine-based app does not run in Catalina. The simplest solution is to install Windows in Parallels Desktop or VMware Fusion and run the app on Windows. This costs money – you have to pay for a copy of Windows – and can be slow and complicated, but is currently the only solution. The most well-known manufacturer of Wine-based software, CodeWeavers, plans to release a Catalina-compatible version, but the job is not easy and it is not clear when the new version will be released.
There is an exception to the rule that Wine-based apps will not run in Catalina: if and only if you run 64-bit Wine, and if and only if your Windows app is a 64-bit app and One that is simple enough to be run under Wine, Wine can run it in a window under Catalina. The most effective way to achieve this is to use the brilliant Wineskin Winery app – an open source project by a programmer using the name doh123 – in the form of an unofficial update from a programmer using the name Gcenx. (The original Wineskin Winery does not run under Catalina.) If there's enough interest in this topic, then we write a guide to guide you here, but there are probably too few 64-bit Windows applications that are usable under Wine's worth it yourself? Interested readers may first look for "Unofficial Wineskin Update," but be prepared to hit your head on the table a few times until you find out.
Apple has not made it easy to run 32-bit apps under Catalina, but it's still possible. If you have found other options, please let us know in the comments section below.