How to find out when macOS was last reinstalled on your Mac

In this tutorial, you’ll learn how to use a simple Terminal command to find out when macOS was last reinstalled on your Mac.

macOS Download

Figuring out how much a Mac has been used is essential when buying a pre-owned computer, especially if the seller no longer possesses the original invoice. While macOS’s System Information application provides some insight into the state of the Mac’s battery, that’s not enough.

Thankfully, you can find out when exactly the owner first completed the initial macOS setup, and that can be quite useful in making an informed purchasing decision. Additionally, checking the warranty status of the Mac will also come in handy.

Find out when macOS was last reinstalled on Mac

1) Launch the Terminal app using Spotlight or from the Utilities folder found inside your Mac’s Applications folder.

2) Type the following line into the Terminal window:

ls -l /var/db/.AppleSetupDone

3) Press Enter to execute the command. Now, you will want to focus on the date listed in the Terminal window, as shown below.

When Mac software was last installed

In my example, you can see I performed a full install of macOS on January 12, 2016.

Important: The listed date is not affected when you install minor macOS updates, nor does it change after you upgrade your Mac to a major new release of the operating system — only a full reinstallation of macOS will change this value.

In other words, if the person you’re buying a pre-owned Mac has never reinstalled macOS on the machine, then this value should give you a good indication as to when precisely they completed the initial setup of the operating system.

As useful as this piece of information is, it’s not entirely actionable without learning additional details about the actual physical condition of the computer you’re purchasing, such as its battery cycle count.

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