Give the external hard drive a suitable name and select “Mac OS Extended (Journaled)” as the drive’s format and “GUID Partition Map” as the drive’s partition scheme.Select your external hard drive (not just a single partition).Click View and choose the Show all devices option.Launch Disk Utility (located in Applications -> Utilities).Connect the external hard drive to your Mac.Unless you’re 100% sure that your external hard drive is freshly formatted based on the above-described requirements, we recommend you go through the following preparation steps: More specifically, it must be at least 64 GB large (the more storage space you have, the better) and formatted using the GUID partition scheme and the APFS file system (Mac OS Extended is no longer supported) To successfully install macOS on an external drive, the drive you want to use must be suitable for the task ahead. Just being curious and wanting to learn something new and potentially useful is the best reason you can have. Of course, you don’t actually need a good reason to install macOS Monterey on an external drive. 💽 Backup system: It’s essential to back up all important files so that you can recover them in the event of a data loss incident, but you may also want to consider setting up a backup operating system on your external drive so that you can minimize downtime as much as possible.👨‍💻 Separating your work life from your personal life: By having two operating systems, you can elegantly separate your work life from your personal life to avoid embarrassing issues with mixed-up email attachments and other similarly unpleasant problems.🧪 Testing: It’s always a good idea to test if a new version of macOS is compatible with all apps you rely on, and you can do just that by installing macOS on an external SSD or HDD.Here are some situations where this approach can be especially useful:

When you install macOS on an external hard drive, you can get your hands on the latest and greatest features without the risk of making your computer unusable.

At the same time, new versions of macOS always introduce attractive new features, and it’s understandable if you want to try them as soon as possible. It’s not uncommon for users to see their Macs become less stable than a hormonal teenager going through a caffeine crash. Seasoned Apple users know that when a new major version of macOS is released, things do always go smoothly.

When It Makes Sense to Install macOS Monterey on an External Hard Drive If you discover that Monterey is too unstable, incompatible, or otherwise unsatisfactory, you can simply format the external hard drive and use it for other purposes, such as storing backups. By learning how to install macOS on an external hard drive, you can safely test everything macOS 12 Monterey has to offer while preserving your current installation intact.

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