Resetting NVRAM

  1. Shut down your Mac.
  2. Locate the following keys on the keyboard: Command (⌘), Option, P, and R.
  3. Turn on your Mac.
  4. Press and hold the Command-Option-P-R keys immediately after you hear the startup sound.
  5. Hold these keys until the computer restarts and you hear the startup sound for a second time.
  6. Release the keys.

After resetting NVRAM, you may need to reconfigure settings for speaker volume, screen resolution, startup disk selection, and time zone information.Power related settings can be controlled by the System Management Controller (SMC) on your Mac. If you are experiencing issues with powering on your computer, sleep, wake, charging your Mac notebook battery, or other power-related symptoms, you might need to reset the SMC instead.

Resetting the System Management Controller (SMC)

In some situations you might need to reset your computer's System Management Controller (SMC).

Before resetting the SMC:
You should only do an SMC reset after you've tried all other standard troubleshooting. Try each of the following steps in this order before
you reset the SMC. Test the issue after completing each troubleshooting step to see if the issue still occurs.

  1. Press Command-Option-Escape to force quit any application that is not responding.
  2. Put your Mac to sleep by clicking the Apple () menu and choosing Sleep. Wake the computer after it has gone to sleep.
  3. Restart your Mac by choosing Restart from the Apple menu.
  4. Shut down your Mac by choosing Shut Down from the Apple menu.
  5. If your Mac isn't responding, force the computer to shut down by pressing and holding the power button for 10 seconds. Note that you'll lose any unsaved work in any open applications.

If you're using a Mac notebook and it's having issues related to power or the battery:

  1. Unplug the power adapter from your Mac and from the wall power socket for several seconds.
  2. Shutdown your Mac.
  3. Physically remove and re-insert the battery (if it's removable)
  4. Restart your computer.

If the issue still isn't resolved after following these steps, you might need to reset the SMC.

On Mac notebooks with non-removable battery
Mac notebook computers that have a battery you should not remove include: MacBook Pro (Early 2009) and later, all models of MacBook Air, MacBook (Late 2009), and MacBook (Retina, 12-inch, Early 2015).
To reset the SMC:

  1. Shut down the computer.
  2. Plug in the MagSafe or USB-C power adapter to a power source and to your computer.
  3. On the built-in keyboard, press the (left side) Shift-Control-Option keys and the power button at the same time.
  4. Release all the keys and the power button at the same time.
  5. Press the power button to turn on the computer.

On MagSafe power adapters, the LED might change states or temporarily turn off when you reset the SMC.

On Mac notebooks with removable battery
Older MacBook and MacBook Pro computers have removable batteries. Learn about removing the battery on MacBook and MacBook Pro.
To reset the SMC:

  1. Shut down the computer.
  2. Disconnect the MagSafe power adapter from the computer if it's connected.
  3. Remove the battery.
  4. Press and hold the power button for five seconds.
  5. Release the power button.
  6. Reconnect the battery and MagSafe power adapter.
  7. Press the power button to turn on the computer.

On Mac Pro, iMac, Mac mini, and Xserve
To reset the SMC on Intel-based Mac Pro, iMac, and Mac mini computers, as well as Xserve:

  1. Shut down the computer.
  2. Unplug the power cord.
  3. Wait fifteen seconds.
  4. Attach the power cord.
  5. Wait five seconds, then press the power button to turn on the computer.

For Intel-based Xserve computers that are not responding, you can shut down locally or by using remote commands. You can also shut down by pressing and holding the power button for five seconds.