The Credential Rotation Vector
If you suspect someone has observed you typing your password in a public space, or if you are handing your Mac over to a junior colleague for temporary use, you must immediately rotate your primary login credential. The Mac login password is not just a barrier to the desktop; it is the cryptographic master key that unlocks your saved Wi-Fi networks, your Safari keychain passwords, and the FileVault encryption protecting your entire hard drive.
How to Change the Mac Login Password
macOS allows you to rapidly overwrite this cryptographic key directly from the primary System Settings interface, provided you know the current password.
1. Click the Apple Logo in the absolute top-left corner of the screen.
2. Select System Settings from the dropdown menu.
3. In the left-hand sidebar, scroll down and click on Users & Groups.
4. Look at the main pane. Your primary administrator account will be listed at the top. Next to your account name, locate the small, grey button labelled ( i ) or the text that says Change… (depending on your exact macOS version). Click it.
5. A pop-up window will appear.
* Type your Old Password into the first field to authorize the change.
* Type your New Password into the second field.
* Type your New Password again into the third field to verify there were no typographical errors.
6. Crucial Step: You must enter a Password Hint. Do not skip this. If you forget your new password tomorrow, this hint is your only lifeline. Do not make the hint the password itself.
7. Click the blue Change Password button.
The operating system will instantly execute a cascade of cryptographic updates across the kernel, updating your FileVault keys and your login keychain simultaneously. The new password is immediately active.