Firmware password
Where do I find a firmware password for a Mac I can’t load without one?
MacBook Air
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See Set a firmware password on your Mac
This support document explains how to turn on a firmware password, how to turn off a firmware password, and what to do if you have forgotten the firmware password:
If you can't remember your firmware password, schedule an in-person service appointment with an Apple Store or Apple Authorised Service Provider. Bring your Mac to the appointment, as well as your original receipt or invoice as proof of purchase.