People usually like to leave traces of their presence before they leave a place as a reminder that they were once there, but when you’re selling your preloved Mac or giving it away, leaving traces behind is one of the last things that you would want to do, so making sure that you wipe your Mac clean before turning it over to its new owner is definitely a must.

Forget potentially embarrassing browsing history (Ahem!), your computer hosts plenty of sensitive information — including ones that may have only been briefly referenced in long buried documents that you may not have even bothered to read — that could get you in serious trouble — both financial and otherwise — if they fell into the wrong hands.

You may be feeling secure with the idea that you have already deleted potentially compromising files, but simply dragging them over to the recycle bin and emptying the trash is only going to delete data at a surface level. This means that people with only basic knowledge of computers are not likely to find anything while casually browsing around, but people with more advanced knowledge of how computers work and plenty of time — not to mention handy tools — to dig around can easily recover whatever traces of information may have inadvertently remained after you deleted your files and use it for whatever purposes that may work to their advantage. So, again, it is highly recommended that you wipe your Mac before turning it over to a new owner.

How to Wipe Your Mac

In this tutorial, we will teach you the step-by-step process on how to wipe your Mac. Please keep in mind, though, that once the wipe has been initiated, you can no longer recover your files, so it is very important that you back them up in some other location before you start. Software and other applications can easily be downloaded and reinstalled after wiping your Mac, but other important files like documents, notes, chat or email logs, as well as images, audio files, or videos that you purchased are going to be gone forever, so we strongly recommend that you do not skip the backing up process.

Backing Up Your Files

There are a couple of ways to backup the files on your Mac. The easiest way to do this is by using your Mac’s default backup program, the Time Machine, or if you would prefer to use a different method, you can also store your data in your iCloud, burn your files to a CD or DVD, or copy your files to another storage device.

To use Time Machine to backup your files,

1. Go to the Apple menu.
2. Select System Preferences.
3. Choose the Time Machine icon.
4. Click Select Backup Disk.
5. Select which disk you’d like to use as a Time Machine backup.
6. Check the BackUp Automatically box in order to automatically backup your Mac to your chosen disks.

Sign Out of Your Apple Accounts

If you are going to be turning over your Mac to a new owner, it is also very important that you sign out of all existing Apple accounts on your computer so that neither your or your Mac’s new owner’s activities will be accidentally linked to the other’s accounts.

How to Sign Out of iTunes

1. Open iTunes.
2. From the menu bar at the top of your computer screen or at the top of the iTunes window, choose Account.
3. Go to Authorizations.
4. Click Deauthorize This Computer.
5. When prompted, enter your Apple ID and password.
6. Click Deauthorize.

How to Sign Out of iCloud

1. In System Preferences, click iCloud, and then click the Sign Out button.
2. When you sign out of iCloud, you will be asked whether you want to remove iCloud data from your Mac. If not, just ignore the message.
3. Your iCloud data will remain on any other devices that are using the same Apple ID.

How to Sign out of iMessage

If you’re using OS X Mountain Lion or later, make sure you sign out of iMessage.

1. Go to the Messages app.
2. Choose Preferences.
3. Choose Accounts.
4. Select your iMessage account.
5. Click Sign Out.

Wiping Your Mac

Once you’ve backed up your files and ensured that you have signed out of your Apple accounts, it’s time to finally wipe your Mac.

To do this,

1. Turn on your Mac.
2. Hold the Command and R keys at the same time then wait until the Apple logo appears on the screen.
3. Select Disk Utility in the Utilities window.
4. Click Continue.
5. Select your Startup disk (usually found under the name “Macintosh HD”).
6. Look at the top of the Disk Utility window and click Erase.
7. Select Mac OS Extended (Journaled) from the options that will appear in the popup window.
8. Click Erase.
9. Once you’re done, select Quit Disk Utility from the Disk Utility drop-down menu.

And that’s it.  Your Mac is good as new. You can now go ahead and reinstall the Operating System and whatever extra programs or applications that you may have agreed to install on the computer before you turn it over to its new owner.