What the SMC does

The SMC is responsible for these and other low-level functions on Intel-based Mac computers:

  • Responding to presses of the power button
  • Responding to the display lid opening and closing on Mac notebooks
  • Battery management
  • Thermal management
  • SMS (Sudden Motion Sensor)
  • Ambient light sensing
  • Keyboard backlighting
  • Status indicator light (SIL) management
  • Battery status indicator lights
  • Selecting an external (instead of internal) video source for some iMac displays

How to know if you need to reset the SMC

These symptoms might mean that an SMC reset is necessary:

  • Your computer's fans run at high speed, even though it isn't under heavy usage and is properly ventilated.
  • The keyboard backlight behaves incorrectly.
  • The status indicator light (SIL), if present, behaves incorrectly.
  • Battery indicator lights, if present, behave incorrectly on Mac notebooks with a non-removable battery.
  • The display backlight doesn't respond correctly to ambient light changes.
  • Your Mac doesn't respond when you press the power button.
  • Your Mac notebook doesn't respond properly when you close or open the lid.
  • Your Mac sleeps or shuts down unexpectedly.
  • The battery doesn't charge properly.
  • The MagSafe power adapter LED, if present, doesn't indicate the correct activity.
  • Your Mac performs unusually slowly, even though its CPU isn't under an abnormally heavy load.
  • A computer that supports target display mode doesn't switch into or out of target display mode as expected, or it switches into or out of target display mode at unexpected times.
  • The illumination around the I/O ports on a Mac Pro (Late 2013) doesn't turn on when you move the computer.

Before you reset the SMC

Try each of these steps in this order before you reset the SMC. Test the issue after each troubleshooting step to see if the issue still occurs.

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

If you're using a Mac notebook that's having power or battery issues, follow these steps:

  1. Unplug the power adapter from your Mac and the electrical outlet for several seconds, then plug it back in.
  2. Shut down your Mac. 
  3. Remove and re-insert the battery, if it's removable.
  4. Restart your Mac.

If the issue still isn't resolved, you might need to reset the SMC using the steps below. 

How to reset the SMC on Mac notebooks

First, determine whether the battery is removable. Most older Mac notebooks have removable batteries. Mac notebooks that have nonremovable batteries include MacBook Pro (Early 2009 and later), all models of MacBook Air, MacBook (Late 2009), and MacBook (Retina, 12-inch, Early 2015 and later). Learn more about Mac notebook batteries.

If the battery is nonremovable:

  1. Shut down your Mac.
  2. Using the built-in keyboard, press Shift-Control-Option on the left side of the keyboard, then press the power button at the same time. Hold these keys and the power button for 10 seconds.
    If you have a MacBook Pro with Touch ID, the Touch ID button is also the power button.
  3. Release all keys.
  4. Press the power button again to turn on your Mac.

If the battery is removable:

  1. Shut down your Mac.
  2. Remove the battery. If you need help removing the battery, contact an Apple Authorized Service Provider or Apple Retail Store.
  3. Press and hold the power button for five seconds.
  4. Reinstall the battery.
  5. Press the power button to turn on your Mac.

How to reset the SMC on Mac desktop computers

Follow these steps for iMac, Mac mini, Mac Pro, and Xserve.

  1. Shut down your Mac.
  2. Unplug the power cord.
  3. Wait 15 seconds.
  4. Plug the power cord back in.
  5. Wait five seconds, then press the power button to turn on your Mac.

For Intel-based Xserve computers that aren't 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.