Reset PRAM on Mac

If you’re having trouble with your Mac, resetting the PRAM might help. It is one of the most common troubleshooting techniques on the Mac. This article tells you how to reset the PRAM and also tells you more about what it is.

Reset PRAM

You can reset the PRAM by restarting your Mac and holding down the keyboard combination Command+Option+P+R. These keys need holding down simultaneously immediately after you restart your Mac, while its starting. While holding the keys, you will hear the Mac boot chime again, this is your Mac telling you the reset has been successful. You can now let go of the keys – the reset is complete, your Mac should now start up normally. The keyboard combination will only work if you hold the keys down before the grey screen appears. If it doesn’t work, restart and try it again.

Did you know? Back in the days of really old Macs, this trick used to be called ‘Zapping’ the PRAM!

How do I know if the PRAM has reset?

The PRAM has only been reset if you heard your Mac boot chime twice. Once when you restart, and then again when the reset has been successful. Afterwards you can stop using the key combination and let your Mac start normally.

Does resetting the PRAM work on all Macs?

The PRAM reset works on all Macs, whether they are Intel or PPC based. Resetting the PRAM using the method in this article works on the iMac, MacBook Pro, MacBook Air, Mac mini and Mac Pro. It also works on legacy Macs including the PowerBook G3, G4, PowerMac G3, G4, G5, the PowerMac G4 Cube, iMac G3, G4 and G5. This trick also works for vintage Macs that were based on the 68k processor architecture (but probably not all of them, try it on your old Mac if you have one and let us know).

What is PRAM?

PRAM means Parameter RAM, and it keeps information about your Mac so that it functions to your specifications. Old Macs used to have a “PRAM battery” which was a 3.6V 1/2 AA battery on the logicboard (motherboard). Newer Macs made since 2006 are Intel-based and use an ordinary CMOS battery that is a lithium CR2032 battery. The PRAM stores the following information:

  • Volume for both system startup and speaker
  • Time zone information
  • Mouse and trackpad scaling and speed information (commonly called mouse acceleration)
  • Keyboard repeat rate
  • Kernel Panic information
  • DVD region settings
  • Default system fonts
  • Startup disk
  • Disk caches
  • RAM disks
  • Virtual Memory (commonly called swap)
  • 32-bit addressing
  • Video and display information including monitor depth, refresh rate, screen resolution, and number of colors

The type of information stored in the PRAM means that if you reset it, you’ll need to specify particular settings afterwards, like your mouse tracking speed and time zone (if you don’t use an Internet time zone server).

When do you need to reset PRAM?

You generally only need to reset PRAM when you’re being affected by the above contents stored in the PRAM. It is often recommended as a preliminary check before trying other things when troubleshooting a Mac. If you’re having problems with your Mac, it is worth a try

Resetting the PRAM is different to resetting the SMC.

More Information

Apple provides a support article about resetting the PRAM.