December 2019 • Macworld 75before selling a Mac.) Tip: If a seller baulks at
providing a password to you directly for something
that can be typed in while booted into macOS
proper – a perfectly reasonable thing to resist – you
can use a slightly hidden feature for iMessages. In
a chat session with Messages for macOS that has
the blue bubbles showing an iMessage connection,
click the Details button in the upper-right corner,
and then click the overlapping screens icon. Select
Invite to Share My Screen. The seller can then
remotely type the password in as required. (They
may want to and probably should change their
iCloud or other password after that, too.)Were one or more accounts created?
If someone else set up a computer, you don’t
necessarily know what’s running on it. I suggest
erasing the drive and reinstalling macOS via macOS
Recovery. However, if that’s not an option or you’re
not concerned, at least delete all unnecessary
accounts and change the password on the main
account, which must have administrator privileges.If you see this
screen at startup,
you need a
firmware password
from the seller to
unlock the Mac