Create a backup

Be sure you have an up-to-date backup of your important files and data. Learn how to back up your data in OS X.

Sign out of iTunes

Open iTunes. From the menu bar at the top of your computer screen, choose Store > Deauthorize This Computer. When prompted, enter your Apple ID and password. Then click Deauthorize.

Learn more about deauthorizing your computer using iTunes, including how to deauthorize all the computers you've used with your iTunes account.

Sign out of iCloud

If you use Find My Mac or other iCloud features on your Mac, you should first archive or make copies of your iCloud data. After that, choose Apple Menu > System Preferences, click iCloud, and then deselect the Find My Mac checkbox.

Finally, sign out of iCloud. In System Preferences, click iCloud, and then click the Sign Out button.

When you sign out of iCloud, you're asked whether you want to remove iCloud data from your Mac. Your iCloud data will remain on any other devices that are using the same Apple ID.

Sign out of iMessage

If you're using OS X Mountain Lion or later, sign out of iMessage. In the Messages app, choose Preferences > Accounts. Select your iMessage account, then click Sign Out.

Erase and reinstall OS X

To reformat your hard drive and reinstall OS X, follow these instructions. After you reformat your hard drive and reinstall OS X, the computer restarts to a Welcome screen and asks you to choose a country or region. If you want to leave the Mac in an out-of-box state, don't continue with the setup of your system. Instead, press Command-Q to shut down the Mac. When the new owner turns on the Mac, the Setup Assistant will guide them through the setup process.

If you still have your iOS device

Before you sell or give away your device, you should remove your personal information. You shouldn't manually delete your contacts, calendars, reminders, documents, photo streams, or any other iCloud data while you're signed in to iCloud with your Apple ID. This would delete your content from the iCloud servers and any of your devices signed in to iCloud.

Follow these steps:

1. If you paired an Apple Watch with your iPhone, unpair your Apple Watch.
2. Back up your iOS device.
3. Tap Settings > iCloud. Scroll down and tap Sign Out. In iOS 7 or earlier, tap Delete Account.
4. Tap Sign Out again, then tap Delete from My iPhone and enter your password. 
5. Go back to Settings and tap General > Reset > Erase All Content and Settings. If you turned on Find My iPhone, you might need to enter your Apple ID and password.
6. If asked for your device passcode or Restrictions passcode, enter it. Then tap Erase [device].
7. Contact your carrier for help transferring service to a new owner. If you aren't using a SIM card with your device, you can contact them to get help transferring service to the new owner.

If you no longer have your iOS device

If the steps above weren't completed and you no longer have your device, use these steps:

1. Ask the new owner to erase all content and settings using the above steps.
2. If you're using iCloud and Find My iPhone on the device, sign in to icloud.com/find, select the device, and click Erase. After the device has been erased, click Remove from Account.
3. If you can't follow either of the above steps, change your Apple ID password. This won't remove personal information that's stored on your old device, but it will prevent the new owner from deleting your information from iCloud.
4. If you're switching to a non-Apple phone, deregister iMessage. 
5. If you're using Apple Pay, you can remove your credit or debit cards at iCloud.com. Choose Settings to see which devices are using Apple Pay, then click the device. Next to Apple Pay, click Remove.