iMac Running Slow? Easy, Common Fixes

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imac running slow

iMac Running Slow? Here’s Your Checklist to Fix It!

Editors note: this post was originally published in August 2015 and was updated in 2017 to reflect new reviews and experiences.

Look no further if you’re living through the frustrating experience of operating an iMac running slow— we’ve got you covered!

1. Check your free disk space

Your issues might come in part from a full hard drive—and you encounter a lot of issues with an iMac when your hard drive space gets low.

To check your free disk space,
  • Open Apple icon 
  • Select About this Mac 
  • Select Storage
macbook air running slow
If you’re running low on storage, we recommend downloading CleanMyMac 3 from MacPaw.

CleanMyMac 3 is simple: it rids your MacBook Air of useless junk files, thus giving you more storage space. 
Though there are many software programs out there, CleanMyMac 3 is the most popular among the Mac user community. It won reader’s choice awards from thanks to its ability to fix issues for hundreds of thousands of Mac users around the world. Best of all, you can try it for free and see what you think. 


Save space on your HDD with CleanMyMac 2!

2. Invest in RAM

Another easy way to increase your iMac’s speed is to upgrade your RAM. RAM, or random access memory, provides “space” for your programs to operate. Your computer stores instructions and data in RAM while powered on— and deletes everything stored in RAM once you turn off the computer. Learn more about RAM with our article on Mac RAM and storage.

Go to your Activity Monitor to see how much RAM you’re using during normal use cases. If you’re brushing up against your limit, it might be time for an upgrade

3. Edit your start up items

Your computer starts up certain apps every time you launch. You want this list to be as small as possible. The less work your computer has to do when it starts up, the faster it launches.

imac running slow

Check your list of startup programs.
To see a list of your startup items, go to:
  • Apple Menu
  • Then System Preferences
  • Then Login Items
Trim this list down to the apps that you need almost every time you start your computer. Remove the others from the list. This doesn’t delete the programs, but prevents them for starting at launch.
Some new programs will auto-add themselves to the startup list. Check this list regularly.

4. Carry out soft resets (SMC & PRAM)

Try carrying out a  couple of soft resets: the SMC (System Management Controller) reset and the PRAM reset. These should help speed up your computer.

SMC reset

The SMC in your iMac is a very important controller. It manages functions such as thermal monitoring, power button response, startup of hard drive spin down cycles, and returning to sleep mode. Your SMC getting out of sync can make your iMac slow, leading to several performance issues.

Thankfully, the reset is pretty quick and easy!

  • Shut down your iMac
  • Unplug the power cord from the wall outlet
  • Press and hold your iMac’s power button for 15 seconds
  • Release the power button
  • Reconnect your iMac’s power cord to the wall outlet
  • Wait for 5 seconds
  • Turn on  your iMac

Though a very simple procedure, the SMC reset can do wonders to a slow iMac, even bringing it back to speeds that you only enjoyed when your iMac was brand new.

PRAM reset

PRAM is short for Parameter RAM. This little memory module also, like the SMC, controls a many functions (like startup volume monitoring, speaker volume control, display resolution control, and the all-important tracking of date and time).

Resetting your iMac’s PRAM is another very easy procedure

  • Shut down your iMac
  • Power your iMac back on
  • Immediately press the following combination of keys, before you see the grey startup screen: Command + Option + P + R
  • Press and hold until your iMac restarts
  • Allow your iMac to startup like normal

Please note that you might have to reset your date and timezone data after a PRAM reset. This is perfectly normal and nothing to be alarmed about. All your data and other settings are still intact.

These two resets can be great to fix your issues with a slow iMac, particularly if the performance issues came out of nowhere, without any rational explanation.


CleanMyMac 3 is available for a free download here.


imac running slow

About the Author
Kylie Larson is a content wrangler, helping both small businesses and large organizations get their message up and out. When she's not writing and organizing online, you'll find her walking the dog, with a camera in hand, riding the Chicago blue line, and in the midst of a home renovation project that never ends. Connect with her at
  1. Smiths_L

    wow, had no idea that a full hard disk can slow down my imac….had just 490 mb of free disk space available…

    ran clean my mac and have 4.8 gb of free disk imac’s faster as well…

  2. sophias+85

    Yup…if you have any sort of anti-virus on your iMac, disable or uninstall it as Macs don’t need anti-virus programs. OS X is closed source software which means that it is virus-protected right out of the box, unlike Windows….

  3. Matthew

    This is a really good tip especially to those new to the blogosphere.
    Simple but very accurate information… Thanks for sharing this one.
    A must read post!

  4. JohnnyLever

    Useful pointers here but I think Michelle’s other points about PRAM and SMC resets are much more useful in helping you speed up your Mac.

    Use the site search to find them.

  5. Rita_Fultone

    Isn’t SMC and PRAM reset applicable just for portable Macs like MacBook Air and MacBook Pro?

  6. JohnnyLever

    Nope. SMC and PRAM resets work just as well for iMacs as well.

  7. Rita_Fultone

    What about Intel based iMac?

  8. JohnnyLever

    What do you mean Intel based iMac? Aren’t all iMacs fitted with either a i5 or i7 Intel these days?

  9. Nicole David

    Lol. Rita – What are you talking about…Intel based iMac? hehehehe..

    Anyways, the SMC reset procedure is the same in iMacs too.

  10. JohnnyLever

    And so is the PRAM reset procedure.

  11. Nicole David

    Awesome. Gonna try out PRAM reset on my iMac. It is running all right but I guess it won’t hurt to try to get some extra boosts in performance!

  12. JLH

    just bought a new iMac on July 5. It has been slow since being hooked up; even the Apple tech people whom I’ve called about mail issues have noticed how slow it is. So I now have a new modem, which supposedly would’ve helped. It did not. It takes about 2-3 minutes for pages to load. I’m mad and frustrated! I’ve re-started the iMac, and also re-booted the new modem. Still snail’s pace here. I find myself using my iPhone all the time because it is so fast – using cellular for that. My iPad is quite slow too, I purchased a new iPad Air just because the old one was so slow, but the new one isn’t any faster. After spending all this $$, I have slower devices than ever before. Should’ve kept my old PC, even that was faster than the new iMac!

  13. Michelle Smith

    JLH, that’s unfortunate. Were you able to apply some of the fixes suggested here and get your iMac to work like normal again?

  14. Ron

    I tried everything: clearing the caches, resetting the PRAM….etc… Nothing helped.

    Then I went into Preferences, selected my printer driver, right clicked, selected RESET PRINTER SYSTEM. After reselecting (via the + sign)…. ba boom. Fast as expected. Thanks to Apple tech support for inadvertently pointing the way.

  15. Ruby

    Thank you. I was so frustrated because my Imac literally took 10 minutes to start up. I removed Norton Anti-virus, removed Spotify and Dropbox as log in items and did the SMC reset. I know that removing files from my desktop would probably help also but I’m already noticing a big improvement.Thanks so much!

  16. Adrian Cole

    Wow! Thanks so much! My iMac was running slow and had done all except doing the soft resets (SMC and PRAM) – that did the trick and it was like a brand new mac again.

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  25. Bernie

    Great tips. Just done the resets on my 2009 iMac. Doesn’t boot any faster but programs open quicker!

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  27. Suzii

    Echoing Ron’s advice to check the Printers and Scanners preferences — I found a paused job for a printer we haven’t owned for months! Deleted the driver and have picked up speed, though I’ll be exploring the other tips, too.

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  30. raywoodrow

    I just reset PRAM and had a most unexpected result 🙁 I have two installations on my iMac (mid 2011 quad core i5): I have kept my SL install intact for stuff that I like and doesn’t run on later OSes and have since installed new up to Yosemite (clean install). When it restarted after the reset, it started up into SL and when I went into system preferences to check the startup disk setting, my Yosemite volume was not an option even though it was still available as a volume on the desktop of SL.
    When I restarted using the option key, I was able to select the correct volume and continue as normal, fortunately. Unfortunately, it seems that zapping PRAM hasn’t changed anything, it still lags a bit, sometimes a lot 🙁 I have previously done the SMC reset, twice.
    To give some background, I am struggling with the no restart/shutdown/logout issue that seems to be a common problem with Yosemite. I came to this page as a result of my investigations. Except for that problem and the sluggishness of the system, everything else seems to run well.

  31. Benjamin

    Excellent advice, thank you very much (iMac 2013)!!

  32. Michael Giambra

    I was looking at 10-15 minute startup and extremely slow operation. I went through the list and found that nothing really applied to me until I tried the two soft resets. The first one (SMC) gave me a slight improvement, but the second (PRAM) reset was like opening the “Nitro valve.” My iMac is back to increíble speeds again. Thanks a heap for whoever put this article together.

  33. Edwin Ingelaere

    Thank you for the tip! SMC and PRAM reset do the trick! (I am running Sierra 10.12)
    Not sure if SMC gave more result than the PRAM reset, but both combined speed up my iMAC (who became extremely slow the last year).

  34. Lana

    OMG THANK YOU!!! My iMac was slower than molasses and I was at my wit’s end. I rebooted many times and even tried both soft resets. The magic trick was CleanMyMac 3. I gladly paid the fee to clean my iMac and WHOA!! It was well worth it.

  35. Stephen Coulter

    I’ve been away for a month and my iMac has been powered off. It is now incredibly slow – I’ve tried SMC and PRAM. I’ve reinstalled OS. It’s got lots of free hard disk space and I’m running 16 GBof RAM – any suggestions. CleanMyMac is installed but won’t load/run. Any suggestions?

  36. Kylie Larson

    Oh man! Have you checked your wifi settings and run a disk repair (see how here: Contact MacPaw if you can’t get Clean My Mac to work because I think that’d be very helpful!

  37. Sheri Miller

    The PRAM reset worked! I can’t believe it! Thank you so much.

  38. NovemberRainne

    I can’t get the PRAM reset to work – it just takes me into Mac Utilities and asks me if I want to restore a back up from my TimeMachine, reload my operating system etc. I am trying it on a 2014 iMac. Was I not holding the keys down for long enough or have i missed something? Thanks

  39. Kylie Larson

    Was your computer completely shut down? And did you hear the chime when it rebooted? Those things should indicate you’re initiating it correctly.

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