It’s like wearing a seatbelt: you are probably fine statistically each time you get in the car if you don’t wear one. If I had to take a guess based on my experience, about one half of hard drives fail before your computer is obsolete.

Seriously, full backups of your entire Mac are not optional.

Click the Options button next to iCloud Drive.As much as I hate to admit it, when it comes to losing data, the question is not “if,” but “when.” If you rely on your Mac for your job, or if your Mac contains valuable information-and whose Mac doesn’t have at least irreplaceable photos?-you must back up regularly or risk data loss.

Select Apple ID in the upper right corner.

If you didn't enable Desktop & Documents Folders syncing in iCloud when you first set up your Mac, you can do so at anytime by following these directions. Here's how to save your Desktop and Documents folder to iCloud Drive: How to add Desktop and Documents Folders to iCloud on Mac Depending on what you have in your Documents folder and what you keep on your desktop, it can take up anywhere from just a few GBs of space to a few dozen GBs of space. If you are nearing your iCloud storage limit at any tier and don't plan on upgrading, it might be better to hold off on using Desktop & Documents Folders in iCloud until you've freed up space in your storage. You can also upgrade your iCloud storage, choosing the package that matches your needs. Even if you don't have very many files or folders on your desktop, the Documents folder is usually where your Mac automatically stores files from third-party apps and programs, and it might be massive.

It does count against your storage and can potentially eat up a lot of it. If you are on Apple's free 5GB iCloud Storage plan and have no intention of upgrading, you probably shouldn't turn on Desktop & Documents Folders syncing in iCloud. You can't choose Desktop OR Documents folders so consider how much space both will use in your iCloud storage.

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