How to Make a Slow iMac Faster

iMac running slow

Over time, an iMac (or any Mac computer) can slow down for many reasons.

Cluttered hard drive, loaded login items and launch agents, too many applications running the background, even macOS itself (e.g. latest 10.15 Catalina) can be the possible causes.

Slow iMac performance may be caused by inadequate hardware too, for example, the internal hard drive is aging and under-performing, not enough RAM (random access memory) to process large app requests, etc.

When an iMac slows down, our work productivity tends to decrease because of the emotional consequences. Scientific study shows that frustration caused by a slow computer affects our health, shocking right?

That’s why we put together this article — sharing a list of actionable tips that help speed up an iMac ​and by implementing some of them you can make your iMac fast again.

1. Optimize iMac Startup

If your iMac takes more than 30 seconds to fully boot up and reach the desktop screen, chances are you’re having too many login items, or launch agents (app services that auto-run in the background). In other words, there might be too many third-party apps or services opening up once you press the start button on the back of your iMac. When the list of login items add up, it’s not surprising that your iMac will slow down.

Fortunately, disabling unnecessary login items is an easy task. Simply click on the Apple logo on the top left of the main screen, click System Preferences > User & Groups > Login Items. Here, you can select any items you don’t want and click the minus sign “-” to disable them.

On the other hand, those sneaky “launch agents” may have been added to your startup as well. Unfortunately, it’s not easy to disable them via the above technique because they are often not shown in the Login Items list. But, you can use an app like CleanMyMac to easily locate and remove them.

Simply download CleanMyMac on your iMac, install and open the app. Under “Extensions”, find the “Launch Agents” feature and here you’re able to disable or enable any helper applications or services. By the way, you can manage Login Items there too.

2. Close Apps Running in The Background

For some applications, even if you have clicked the red “x” sign located on the upper left corner, they may be still running in the background. If you have too many such processes running at once, your iMac speed can be significantly affected, worse yet, the whole Mac freezes up to death. And you’ll have to force quit apps or have a hard reboot.

To see what apps and services are consuming lots of system resources (CPU, memory, battery, etc.), use the Activity Monitor app (or iStat Menus) to find them out. Apple has a support article on how to properly use this utility. See this video for more:

3. Clean up iMac Hard Drive

All Macs will run slowly once the startup disk is almost full. Some macOS features or utilities might even malfunction under low storage.

Also, lack of free space is often a cause of more frequent hangs, freezes, and app crashes.

To move more space on your iMac hard drive, your first step is to get an overview of the storage.

To do so, click on the Apple icon, then About This Mac. Under the Storage section, you can see how much space is available on the current disk. Different blocks of color indicate different file types, such as movies, photos, or apps.

Then, clean those unnecessary files such as system junks, unused apps, large old items, etc. Again, CleanMyMac is a time-saver, it helps you determine what specific files are taking up the most space and indicate which are safe for removal or transfer.

Meanwhile, you can also use Gemini 2 to quickly get rid of those duplicate and similar files (especially photos). Both CleanMyMac and Gemini are designed and developed by the same company.

4. Run The Right macOS Version

Depending on the iMac model you are using, you may want to double-check whether the macOS version your iMac runs is the best option. For example, the latest macOS Catalina does not always guarantee better performance, especially it requires at least 4GB of memory and 12.5GB of available storage space, or up to 18.5GB of storage space when upgrading from OS X Yosemite or earlier.

If your the hardware configuration of your iMac is a bit behind, chances are it’ll run slowly after the update. In fact, many iMac users reported the issue.

So, know your iMac and run the right macOS. To check what macOS version your iMac is with, click Apple logo > About This Mac, there you’ll see the information. Then you can choose to upgrade to a newer macOS or downgrade to a lower one.

5. Remove Unwanted Applications and Extensions

How many times have you downloaded an app or browser plugin, but only used it for once and later you totally forgot its existence?

Days and months later, you may surprisingly find that your iMac is filled up with such unneeded apps/extensions. Most of them won’t do any harm except taking some storage, some may run quietly when you start up your Mac or while you surf the Internet via Safari, Chrome, Firefox, etc.

So, it’s always a good idea to remove such unneeded apps and plugins to give your iMac a little bit performance boost.

The easiest way to start with is to go to the Applications folder, drag and drop those unwanted apps to the trash and empty Trash.

To Clean up browser plugins/extensions, open the settings of your browser and you should be able to find the right place to manage those extensions. For example, I’m using Chrome (ver. 64 for Mac), just click the three-dot icon, then More Tools, and find Extensions. There I can see all installed plugins, and choose to delete or disable those unwanted.​

6. Add More RAM

RAM (random access memory) plays an important role in processing app requests. If you are a designer or developer who uses an old iMac for video or photo editing projects, chances are RAM may be the bottleneck.

When RAM is used up, your iMac has to switch to use disk virtual memory which will ultimately lead to slow iMac performance.

The solution? Consider adding extra memory! If you decide to do so, be sure to check how many GBs your iMac is able to add from this Apple resource page. For example, most 27-inch models, the base memory is 8GB and you can add up to 32GB.

For RAM upgrade options, consider Crucial 16GB Kit (8GBx2) and OWC 32GB for 2017 iMac 27-inch with Retina 5K display.

Also, don’t forget to check out this video before opening your iMac mainframe to install additional RAM.

7. Replace Your iMac Hard Drive with an SSD

For older iMacs, replacing the current hard drive or fusion drive with an SSD (solid-state drive) can significantly improve your Mac’s speed and performance. Similar to adding more RAM, be sure to check which SSDs are compatible with your iMac model.

For iMac SSD options, consider this OWC SSD ​Upgrade Bundle if you’re using a 2012-2015 iMac or OWC Mercury Electra you’re on a 2011 model iMac.

This video shows everything you need to during the process of replacement.

That’s all that we wanted to share out with you. I hope you find this iMac performance troubleshooting guide useful. Let us know which way(s) you find most useful in speeding up your iMac? We’re here to hear from you.

11 thoughts on “How to Make a Slow iMac Faster”

  1. Andreas,
    I have a 2011 iMac I hang onto since it has a cd player/burner and is handy to watch old fashion DVD’s. I have 12GB of memory installed and wonder if I should install a new HD that you mention in this very useful tutorial. BTW, one of the best and most comprehensive I’ve come across so kudos to you.
    This Mac is running very slow and often takes up to a minute to move from one task to another. Would it benefit from a new HD or am I missing something as far as cleaning. In this current Stay At Home I won’t mind an interesting project but I also don’t want to do something unnecessary. I have a version of Clean My Mac which I just checked and it tells me I have 2.77 GB of memory. Do I clean that first? I’m by no means an expert such as yourself and may step right over the obvious, my knowledge of how all the moving parts work is limiting but then there are people such as yourself to reach out to.

    Sincerely,

    Wyatt Easterling

    Reply
  2. I have the an iMac(21.5-inch, Late 2012) WITH A 2.7 GHz Quad-Core intel Core i5.
    What do you think is the best SSD drive and RAM to help improve my iMac and make it run a lot faster.

    Reply
  3. I have a 2011 imac and the quoted max memory is 16gb but I have 20gb as all 4 memory slots are taken 2x8gb and 2x2gb is this in any way harmful?

    Reply
  4. I have just bought a new iMac after loving my last 21in iMac for 10 years. I have a 2020 27in Retina 5k 3.3 6 core i5 and have upgraded to 64gb ram to improve. It come with os Catalina 10.15.6. It has Intego antivirus, and vpn.
    Even after the upgrade it is really, really slow on the internet using Safari.
    My old Mac has 8gb of ram and is lightening compared.
    I am at a miss as to what to do? Do you have any ideas please?

    Reply
  5. Hi! thank you for this information. I have a 27in imac since late 2013 and now the apps are starting to crash and the startup is taking long as well as other things. My current RAM is 8gb and here it says it can be upgraded up to 32gb. So, do you think my performance problem might be indeed regarding the RAM? because I’m considering buying more and also was recommended to replace the disk with a ssd.
    On the other hand, Catalina is supposed to be the last mac os version this model will support, i don’t know if is really convenient to upgrade this iMac’s disks or just get a new iMac, what do you think? I use mostly Adobe products. Would I still be able to use this “fixed” iMac properly even though I won’t be able to upgrade its system not so much later?

    Reply
  6. I have an early 2012 Imac i7 16gb ram and its really slow. Is there any way to upgrade this or does it have to be brought in to a mac store for that to happen

    Reply
  7. I bought an external SSD for my 2017 iMac, found an easy follow along youtube video and it has sped up everything on the Mac. Boot up times from from a couple minutes to around 20 seconds. Opening an app from from around 30 seconds to about 3 seconds. Everything on my mac not runs tremendously faster. It’s sad that my $1,100 machine is so slow but my $80 fix has made it enjoyable to use.

    Reply
    • Sorry for typos. Since I couldn’t edit, here is my cleaner copy. lol
      I bought an external SSD for my 2017 iMac, found an easy to follow Youtube video and it has sped up everything on my Mac. Boot up times went from a couple minutes to around 20 seconds. Opening an app went from around 30 seconds to about 3 seconds. Everything on my mac now runs tremendously fast and as fast as I hoped when I bought it a few years ago. It’s sad that my $1,100 machine is so slow but my $80 fix has made it enjoyable to use. I didn’t want to spend $2k on a machine but also didn’t realize that the 8gb DDR4 drive was so slow. not ideal but the $80 Samsung SSD saved the day.

      Reply

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