Reset NVRAM on your Mac
If one or more settings stored in NVRAM aren't working as expected on an Intel-based Mac, resetting NVRAM may help.
Do you need to reset NVRAM?
NVRAM (or PRAM) is a small amount of memory that your Mac uses to store and quickly access certain system settings, such as sound volume, display resolution, startup-disk selection and time zone. These settings vary by Mac and the devices you're using with it.
Normally you can manage these settings in System Preferences, without resetting NVRAM. If one or more settings still aren't working as expected, resetting NVRAM may help. Resetting NVRAM is also the recommended final step before you sell, give away or trade in an Intel-based Mac.
If you have a Mac with Apple silicon
Find out if you have a Mac with Apple silicon
The steps to reset NVRAM don't apply to Mac computers with Apple silicon, and aren't needed on those computers.
If you have an Intel-based Mac
If you're not using a Mac with Apple silicon, you're using an Intel-based Mac.
How to reset NVRAM
Shut down your Mac.
Turn on your Mac, then press and hold these four keys together immediately: Option, Command, P, R.
Release the keys after about 20 seconds, during which your Mac may appear to restart. For example, you may hear a startup sound more than once, or see the Apple logo more than once.
When your Mac has finished starting up, you may need to adjust any system settings that have been reset.
Find out more
If your Mac doesn't seem to recognise Option-Command-P-R during the startup process, consult the guidelines for using startup key combinations.
If you're using a desktop Mac instead of a notebook, and settings such as sound volume or time zone are being reset every time you shut down and unplug your Mac, you may need to get your Mac serviced to replace the small battery that NVRAM uses so you can retain these settings when your Mac is unplugged.