iMac Running Slow? Easy, Common Fixes

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Look no further if you’re living through the frustrating experience of operating a slow iMac computer– we’ve got you covered. Your slow iMac can come from many different things, and there’s a lot you can do to to try and fix your issues.

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

1. Check free disk space

Your issues might come in part from a full hard drive– you can encounter a lot of issues with OS X when your hard drive space gets low. With every update, Apple tweaks its OS X to ideally work on more powerful specs, leaving you a bit in the dust if you have only an old iMac.

Sometimes a full hard drive can lead to crashes and other usability issues. There are some software utilities on the market that could be just what you need– we recommend CleanMyMac 3, an Apple community approved software program that can free up GBs of hard disk space in a matter of minutes, restoring your iMac’s original speeds in no time.

CleanMyMac 3 is available for a free download here.

Besides freeing up hard disk space, CleanMyMac 3 will also clean out your iPhoto folder, removing all duplicate file photos and will even get rid of useless apps that might be slowing down your iMac further, which really helps improve startup times. Using this software is probably the easiest way to fix your issues with a slow iMac.

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 everything stored in RAM is deleted once you turn off the computer. 4GB is somewhat of a minimum for a lot of people, but some users can see performance benefits from using 12 or 16 GB of RAM– it just depends on what you’re doing. People who do a lot of photo or video editing  are more likely to see increased performance with more RAM.

iMac RAM Upgrade

Increase your iMac’s RAM to significantly improve performance.

Now, depending on which model iMac you have, you maybe able to increase RAM from anywhere between 2GB and 32GB. As an example, if you bought your iMac sometime in early 2006, you can increase your RAM by only 2GB. If you bought your iMac in late 2009, you can increase RAM by as much as 16GB. The latest iMacs can accommodate as much as a 32GB RAM upgrade that will give you a tremendous boost in performance speeds.

For a full and precise list of the maximum amount of RAM that your particular iMac can take, please visit this official Apple page on memory upgrades for the iMac.

You might not need more RAM– 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 a list of apps every time you launch it, and these are (unsurprisingly) called startup apps. You want this list to be as small as possible– the less work your computer has to do when it starts up, the more quickly it’ll launch. Furthermore, if you’re not using these programs they’ll be wasting system resources, also making your computer run more slowly.

slow iMac - Startup list fix

Take a look at your startup login list and decide if you want the listed applications to really start up as you start your iMac

Check your list of startup programs by going to Apple Menu –> System Preferences –> Login Items and you’ll be greeted by a list of the programs on your computer. Trim this list down to Keep only the apps that you use the most often– don’t worry about things you won’t need almost every time you start your computer.

Remove the others from the list. You won’t be deleting the programs, but rather simply keeping them from launching unnecessarily when you start the computer.

Sometimes newly installed programs will automatically add themselves to this list– meaning your computer will slow down over time as you add more programs to the hard drive.

4. Carry out soft resets (SMC & PRAM)

Try carrying out a  couple of soft resets called the SMC (System Management Controller) reset and the PRAM reset. These should help return your computer to a state closer to when you first bought it– speeding it up and making it much easier to use.

SMC reset

The SMC in your iMac is a very important controller. It manages many functions like 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 fix 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. Though very small in quantity in terms of memory allocation, this little memory module also, like the SMC, controls a many functions like startup volume monitoring, speaker volume control, display resolution contro,l 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.


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Don’t forget to check Apple’s App store for all your computer productivity needs.

About the Author
Michelle, author at Mach Machines. A tech lover and an insatiable latte drinker. Michelle blogs about improving the personal computing experience.
  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.

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