Reset SMC/NVRAM

Every Intel Mac contains two components that manage system configuration: NVRAM and the SMC. NVRAM (non-volatile randomaccess memory) stores settings including startup disk selection, screen resolution, time zone, and sound volume.

The system management controller (SMC) governs the system’s response to the power button (or opening or closing a MacBook display lid), battery and heat management, the ambient light sensor, keyboard backlighting, indicator lights, and external video input on select iMacs.

Resetting NVRAM or the SMC shouldn’t be necessary without good reason, but most experienced Mac users have seen it fix unexplained glitches and it won’t harm your Mac.

To reset NVRAM, power on your Mac and hold Opt+Cmd+P+R immediately, then keep them held until the Mac finishes starting up, sometimes restarting itself again during the process.

To reset the SMC on any desktop Mac except an iMac Pro, shut down the Mac (don’t just put it to sleep), physically disconnect the power cable from the Mac, wait 15 seconds, plug it in again, wait five seconds, then press the power button to start up the Mac.