How to Wipe a Computer Clean of Personal Data

Got an old laptop laying around? By selling it or donating it to someone, you can clear up space in your home, maybe earn a little cash, and extend its useful life, delaying the inevitable one-way trip to the local landfill.

But how do you keep the next owner from accessing photos, financial documents, and other private data once stored on the hard drive?

Short of removing the drive altogether, the best solution is to perform what’s known as a factory reset.

As for why you can’t simply clear out your Downloads folder and log out of your accounts, Matt Ham, owner of the service company Computer Repair Doctor, explains that manually purging files isn’t enough.

“You’re likely to forget things like passwords saved in browsers and personal data in the deleted items folder. Or you can miss deleting some important files altogether,” he says. “Reinstalling your system before sale is a much safer alternative.”

In most cases, wiping a computer with a factory reset will be sufficient to safeguard your personal data. So if you’re handing off your old computer to a friend or sibling, or donating it to a well-known charitable organization, the steps listed below should suffice.

Theoretically, however, a determined hacker may be able to use advanced data recovery software to unearth your old files, even if you’ve performed a factory reset. That’s why Richard Fisco, who oversees electronics testing for Consumer Reports, cautions that some consumers may feel more comfortable removing the hard drive altogether before sending the laptop off to its new home.

“The gold standard in hard drive security consists of using a pointy nail and a few swift swings of a hammer,” he says half-jokingly. “Just make sure you’re wearing safety glasses.”

Of course, you’ll want to back up any important data you may have to another drive, or to the cloud, before you perform a factory reset (or, perhaps, break out the hammer and nails). But once that’s over and done with, and you’ve verified that the data has been safely backed up, actually carrying out a factory reset is simple whether you’re on a Mac, Chromebook, or Windows PC.

Apple Users

Apple last fall introduced computers using its own homegrown M1 processor, also known as Apple silicon. You’ll need to perform different steps to perform a factory reset on one of those (see below) than on a Mac with an Intel processor.

Once again, before you begin, be sure to back up important files and then sign out of iCloud. That can be done in the Apple ID section of the System Preferences app.

You should also copy your keychains to a flash drive. This step isn’t required, but transferring those account names and passwords onto your new machine will save you the hassle of re-entering the WiFi password at the local coffee shop or the login info for online retailers.

To perform a factory reset on Intel-based Macs, hold down the Shift + Option + Command + R keys while starting up your Mac until the Apple logo appears on the screen. This will reinstall the operating system that came with your Mac. Alternatively, you can hold Command + R to reinstall the latest MacOS installed on your Mac or Option + Command + R to upgrade to the latest version of the OS compatible with your computer.

Once you’ve done that, the Utilities window will pop up in the middle of your screen. Open the Disk Utility and erase your built-in hard disk. Make sure to select the disk, not the volume name listed beneath it. Then select MacOS Extended (Journaled) format and quit Disk Utility when the process ends.

To finish the reset, navigate back to the Utilities window and choose Reinstall MacOS (or OSX) to reinstall the original operating system.

After the reinstall, the Mac will begin the setup process. This should look familiar if you’ve set up this computer before. If you’re selling your computer, you can skip setup by pressing Command + Q and let the new owner complete that process.

For M1-based Macs, Apple says you need to make sure you’re running the latest version of MacOS before you get started. You can do that by clicking System Preferences in the Apple Menu in the upper left-hand corner and then clicking Software Update. Once that’s completed, turn off your Mac and then turn it back on while holding down the power button. Eventually a screen will appear featuring a black background and two icons: your hard drive (called Macintosh HD unless you changed it) and Options. Click Options.

At this point, you may be asked to input a username and password. Once that’s done, click Disk Utility > hard drive (again, called Macintosh HD unless you changed the name) in the left sidebar > Erase. You’ll be prompted to enter a new name (consider Macintosh HD, for simplicity’s sake) and Format (which should be APFS).

Now click Erase Volume Group, enter your Apple ID when prompted, and click Erase Mac and Restart. You can then follow the onscreen instructions, which include things like selecting your language and WiFi password.

Windows Users

Before beginning the factory reset process, back up all important files. You might also want to make sure that you have the serial numbers and/or usernames and passwords for any registered apps handy for when you go to reinstall them later.

The process for resetting your PC differs slightly for each version of the operating system. For Windows 10, go to the Start Menu and click on Settings. Then navigate to Update & Security, and find the Recovery menu. Next, select Reset this PC and choose Get Started. Follow the instructions to revert your computer back to when it was first unboxed.

You’ll be asked to choose whether you want to erase data “quickly” or “thoroughly.” Opt to erase data thoroughly. It’ll take a little longer, but it makes it more likely that your data is deleted permanently. While there’s no absolute guarantee the data can’t be retrieved after a reset, this simple step increases your security.

Chromebook Users

Chromebook users have the easiest time wiping their laptops. Unlike Apple and Windows users, they already have most of their files stored online in Google Drive. So there’s little to back up before you begin the process.

To start a factory reset, click on the Launcher. Open Settings and scroll down to the Advanced section. From there, find the Reset Settings, and under Powerwash, click Reset. This will prompt a restart, which will flush away all your personal information.

If you’re ready to sell or donate the computer, don’t log back in—the next person who logs in becomes the Chromebook’s primary user.

About John Paul

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