I have a iMac Retina4K from the end of 2015 with 3.1GHz Quad-Core i5 and 8GB DDR3 on 21" with a second monitor attached, and a HDD-disk. macOS is Catalina and I am running Firefox, Adobe InDesign and Adobe Illustrator most of the time. Since I upgraded to Catalina my Mac is soooo slow that starting up in the morning until anything really runs (i.e. I am able to click on an app) takes up to 10 minutes with no applications opened yet.

Opening up Illustrator works in 6 of 10 times, else it just freezes. If opened it does work okay though. Firefox freezes also on a regular basis. I never open up more then 3 applications at the same time, have no widget etc running and I got hundreds of gigabyte diskspace left.

I get it, that this isn't the newest device but shouldn't the OS and some really simple task like opening up a browser be "there" in less then 5 minutes?

My question though is a different one: If I'd set up/reinstall the Mac completely new with Catalina (as I am bound by Creative Cloud to it) should that speed up my described routine or is the current scenario just what I can expect from the combination of that hardware/software combination?

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    Yes, if you've got a hard drive in there, you should check whether it's failing. (Ideally, you should replace it anyway with an SSD, either externally or internally.) If your drive if completely full, too, this may have an effect on speed.
    – benwiggy
    Commented Jun 1, 2021 at 10:44
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    @benwiggy So replacing my current disk (if at all possible) with a SSD could have quite an impact? I do have 300 TB space left, so space isn't the problem I guess..
    – Daiaiai
    Commented Jun 1, 2021 at 10:50
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    I bought my folks one of those late HDD iMacs. 10 mins startup time is not exceptional. They really really need an SSD. btw, I presume you mean 300GB space… no-one has yet been able to manufacture a 300TB drive ;))
    – Tetsujin
    Commented Jun 1, 2021 at 11:20
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    replace the HDD to a SSD
    – BabyBoy
    Commented Jun 1, 2021 at 11:37
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    With a HDD and 8 Go of RAM, it's normal that Catalina be slow and the problem on this Mac Model is difficult add memory and/or replace HDD by SSD. An extern thunderbolt 2 SSD may help you, but it's very difficult to find those enclosures models.
    – user415185
    Commented Jun 1, 2021 at 11:38

1 Answer 1


You can use Activity Monitor (in /Applications/Utilities) to see what processes are taking the most CPU and Memory, and monitor disk input and output. This may help to identify what is causing the slowness.

However, the most likely cause (in the absence of any other info) is the presence of an internal mechanical hard drive, either by itself or as part of a 'Fusion' drive.

Mechanical hard drives are much slower than modern 'solid state' SSDs. If your Mac has to 'swap' memory data to and from the disk, then this will slow things down dramatically. Also, the drive is at the end of its useful lifespan, and may show signs of failing.

While taking an iMac apart to replace the drive may be of moderate difficulty, you would do better to use an external SSD. Old Thunderbolt 2 enclosure are harder to find these days, but even a USB3 SSD will be faster.

Apple continued to install hard drives in iMacs for many years after it was using SSDs in its other Macs. So, in reply to the question 'is this normal for an iMac', the answer is sadly, yes.

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