Safe Testing: How to Try macOS Catalina Before Upgrading

ByThe Answerlode Editorial Team

Testing macOS Catalina on an External Drive

Your approach is solid: cloning your OS and apps drive to an external USB-3 or SSD and upgrading that copy of Catalina lets you test the new system thoroughly without touching your working setup. If something goes wrong or you find incompatible apps, you simply boot back to your internal drive and you’re back where you started.

Why This Method Works

The Mac mini Late 2012 fully supports macOS 10.15 Catalina, so hardware compatibility isn’t a barrier. Your two-drive setup actually makes this easier: your user data lives on a separate SSD, so testing Catalina on a clone of just the OS and apps drive keeps your files completely untouched.

macOS can boot from external drives—hold the Option key at startup to select which drive to boot from. This means you can keep your internal drive as a fallback while you live with Catalina for days on the external clone, then switch back instantly if needed.

Before You Start: Audit with Go64

Running Go64 before any cloning is the right first step. This free tool from St. Clair Software scans your Mac for 32-bit applications, which is crucial because Catalina completely drops 32-bit support. Once Catalina boots, any 32-bit apps simply won’t launch—there’s no workaround during normal operation.

Go64 shows you which apps are 32-bit and links to developer websites, so you can plan upgrades or find alternatives before you commit to Catalina. This is your real test: if you can live without or upgrade your 32-bit software, Catalina is safe for you.

How to Clone Your Drive

You have two main options:

  • Carbon Copy Cloner or SuperDuper!—These paid tools reliably create bootable clones. They copy everything, preserving permissions and making a drive that boots exactly like your original.
  • macOS Disk Utility—Built-in and free. Format your external drive, then use the Restore function to copy your internal OS/apps drive to it.

Whichever tool you choose, the external SSD must be erased first, so make absolutely sure it contains nothing you need. A 250GB or larger external SSD is ideal so you have room for the OS plus your apps after the Catalina upgrade.

Upgrading the External Clone

Once your clone is complete, boot from the external drive (Option key at startup). Download Catalina from the App Store, run the installer, and let it upgrade the external copy of your OS. Any 32-bit apps you identified with Go64 will either prompt you during installation or simply fail to run afterward.

Live with Catalina on the external drive for a few days: launch your everyday apps, test your workflow, check for crashes or slowness. If you hit a showstopper—an essential app that won’t run—just restart and hold Option to boot back to your internal 10.14 drive. No data loss, no damage.

The Real Gotcha

Your mention of apps on the external drive affecting user data is thoughtful, but you’re protected by your separate data SSD. Apps running off the external clone can’t touch your data drive unless you explicitly tell them to. However, be aware that if you ultimately decide to upgrade your internal drive to Catalina, you’ll need to handle the same 32-bit app cleanup—this test just lets you see the impact first.

After Testing

If Catalina works well and you want to upgrade your internal drive, you can use the same cloning tool to copy your updated external drive back to your internal OS drive, or do a fresh Catalina install and use Migration Assistant to move your apps and settings. If Catalina isn’t right for you yet, keep your internal setup as-is and revisit later.

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