How do I log in to Mac OS X if I forgot the administrator password?

Answer: Fortunately, if you forget the password for your admin account in Mac OS X, you can reset the password and regain access to your computer. To reset the admin password, follow these steps:

1. Insert your Mac OS X Installer disc (this is typically the "Disc 1" installer disc that came with your Mac). You can also use a newer Mac OS X Installer disc purchased after your bought your computer.
2. Start up your computer from the Installer disc. To start your Mac from the CD or DVD, hold the "C" key as soon as you hear the startup chime. Keep holding the "C" key until the Apple logo appears on the screen. If you performed this step correctly, you will hear the optical drive spinning as your computer boots up. The boot process may take longer than a normal restart since your computer reads data from an optical disc more slowly than the hard drive.
3. Once the boot process finishes, choose a language if prompted.
4. In Mac OS X 10.6 or later: Select Utilities → Password Reset.
   In Mac OS X 10.5 or 10.4: Select Utilities → Reset Password.
   In Mac OS X 10.3: Select Installer → Reset Password.
   
5. Select your primary Mac OS X startup disk (named "Macintosh HD" by default).
6. Select your administrator account from the drop-down list. (Don't select the "root" user, since this is a different account).
7. Enter a new password and reenter it in the next field.
8. Click the "Save" button.
9. Close the Reset Password window.
10. Quit the Installer (Mac OS X Installer → Quit).
11. Click "Restart" when prompted.

When you restart your computer, you should be able to log in using your administrator account and the new password you selected.

Important: Anyone can reset a Mac's admin password using a startup disc. Therefore, it is possible for someone else to gain access to your files even if you have password-protected your user account. To fully secure your files, you can use Mac OS X's "FileVault" feature, which is available in the Security System Preference. However, if you turn on FileVault and forget the FileVault password, you will not be able to recover your files.

Published: December 3, 2010 — by Per Christensson