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

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 has first completed the initial macOS setup and that can be quite useful in making an informed purchasing decision. In this tutorial, you’ll learn how to find out when macOS was last reinstalled on any Mac using a quick Terminal command.

How to find out when macOS was last reinstalled on Mac

1) Launch the Terminal app from the Utilities folder found inside your Mac’s Applications folder, or use Spotlight to launch Terminal.

2) Type the following line into the Terminal window:

ls -l /var/db/.AppleSetupDone

3) Press Enter to execute the command.

You’ll 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 my example, I installed several macOS system updates as well as upgraded my computer to macOS Sierra since January 12 of last year.

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.

To see your Mac’s battery cycle count, choose About This Mac from the Apple menu and click the System Report button on the Overview tab.

MacBook battery cycle count

Now select the Power tab in the lefthand column, underneath the Hardware section.

In the righthand panel, you will find a Mac notebook’s battery cycle count next to Cycle Count, as showed above. macOS installation or reinstallation does not affect the battery cycle count

A low battery cycle count doesn’t necessarily mean that the computer has been rarely used if the owner has used it predominantly while connected to a power source. Additionally, the owner may have replaced their Mac’s battery so that’s another thing to factor in when buying a pre-owned Mac.

At any rate, take the battery cycle count and the date macOS was last reinstalled with a grain of salt and use these values only as a guidance when buying a used Mac.

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