iMac slows down after Big Sur installing

Hi, I just bought a new MacBook Air 2020. I got an update notifying me to upgrade the OS to Big Sur. I'm looking for any recent updates on the OS please, as by the looks of this question in forum, Big Sur is a big no no.

Is it worth it, or should I keep Catalina for now, until the next version of OS is released?

same problem with "MacBook Pro (Retina, 13-inch, Late2013)".
ran perfectly fine and snappy until yesterday when I let it do the update.

now boot time is horrible, after logging in it takes forever to show my desktop and even then it isn't done loading because the search cannot even find "sound" (settings) for example, it just does nothing.

cmon Apple, I did give you this one chance on friday and you seem to **** it up already.

iMac slowed down after Big Sur update! yikes. apple fix it asap!!! takes a long time to switch between apps, do usual stuff on the iMac. Mail app has been the worst hit, taking time to load messages and sometimes not even able to download messages! c'mon apple, you can do better.

To reply to some of the questions of the thread:

Yes most of the user having slow down have upgraded from Catalina, but that is exactly what is expected from a mac.
My fusion drive is still properly configured and recognized by the system.
A clean install without time machine is not a solution but rather a workaround: i have many customisation to apps and system i hardly remember how i did them; plus i have one year worth of time machine backup I would like to keep.

Beside that I keep my user profile very clean, I manually purge old files from time to time I honestly cannot believe my settings can be the reason for that slowness. I guess it has more to do with what is in the system folder, but that is out of my control and it is apple duty to keep it clean and lean.

Big sur might be intentionally crippled on intel mac to move users to new Apple Silicon based macs, but i really hope that is not the case. I have been updating my mac yearly since 2015 with new macOs's and Big Sur is the worst update so far in terms of performance drop. I highly suggest against updating to Big Sur: if you're happy with Catalina, keep it or you will be disappointed.

I’m also having issues with MacOS Big Sur. My Macbook Pro 2017 has gotten significantly slower :(

Same here!
iMac 2019 is slow, terrible!!! Like an old Windows PC.
I think "fusion drive" can be the problem. (with MacPro 2019 the system runs ok)
Perform clean install. Same problems!
I hope that the "silicon migration" can't be a nightmare for Apple users!!!

Please Apple, fix the problems!

Same here after update to Big Sur!!! My iMac 2015 takes forever to start up and show the icons on the desktop even there is only few of them. Everything takes forever now. Also it happened few times that it gets frozen and it restarted the system by itself. Can't work like that. Needs to be fixed ASAP.

An update to my earlier post (2015 iMac 27" with fusion drive): The following steps worked for me:

1. Boot with option key down into a Big Sur installer USB flash drive

2. From terminal, execute 'diskutil resetfusion' to wipe, reformat, and rebuild, the built in fusion drive

3. Return to main recovery menu and install Big Sur from the USB flash drive.

No noticeable slow down.

My iMac pro is extremely slow. Clang/llvm build takes from minutes to hours.
CPU utilization is low < 10% with 18 cores. It appears to be blocked by disk or something else.
Launching a clang in a separate terminal while ninja is running takes a minute even without any input!
So disappointed with this update.

Just giving an update, might help some people

I upgraded from Catalina to Big Sur and had the same slowness that everyone here is complaining about. I have a late 2015 iMac with a fusion drive. At the suggestion of Apple support I created a new user with admin rights and started transferring all data from the existing user to the new user. This was a real pain but I think it's easier than doing a complete new install

It's now a month in and I see no issues, my mac is as fast as it always was with the new user. When I try to login with the old user I still have the same slowness. Just for reference I'm a software developer and sometimes have multiple cpu/memory intensive applications open at the same time. Right now I have Eclipse, Intelij, a tomcat instance and a SQL server on docker (don't ask...) running with no issues!

Apple is impressing me with how determined they are that I quit using their products.

I'm astounded that after all these year, they insist on screwing their things up so badly.

So this is the last time I'm going to buy a laptop from them, ever again.

I do not understand how can a laptop from 2016 that worked just fine before Big Sur, to run like a freaking dirty sock!

You sock apple! Reaaaaaally bad!

Not sinking money into your products ever again.

The same problem here. I just recently bought MacBook Pro 13" 2019 1,4 and soon after updated the iOS to Big Sur. Ever since then it started taking too long to start up the computer, and every time it is put on sleep or logged out it takes between 1-2 min to enable me to type in the password or scan my finger print. My old MacBook Air from 2014 seems to work much faster than the new MacBook Pro. I tried cleaning up all the cache memory, closing down all the applications opened before I log out, nothing helped. Seems that the Big Sur is really pain for Mac. Cannot see ay reasonable solution to this. Anyone has any suggestion?

Hi guys

I need to ask the community the following:

For 2 days ago woke up to find that my IMac 2019 intel i9 crashed over the night and both of my external screens stoped working!

I basically started then to Google about the issue both new usb-c adapters changed the cables nothing worked.

That was the time when I decided to call Apple and after talking with them for 2 hours the decision was to upgrade to Big Sur. BIG MISTAKE!!

The machine started lagging got lines on my screen and the external screens are still not working.

Then I decided to erase the HDD and reinstall Big Sur. SECOND BIG MISTAKE!!
It got even worse :(

Then I decided to downgrade to the previous Catalina OS from a bootable USB.
The machine is still lagging and the screens still not working. Then I decided to downgrade to Mojave the OS the machine came with, well still same lagging and screens not working :(

Everytime I did the above solutions I did a clean install

Now any of you amazing ppl can have more to add to my solutions?
I got green light from Apple that Incan send the machine to one of there service place but my problem is that i live really remotes and I will be without a PC for like a month, that is why I am asking you ppl for more brainstorm maybe I can fix the problem without sending the machine to Apple?

what resolves partially the issue of s l o w n e s s is: 1-turn off the imac 2- unplug from the wall 3- wait 15 seconds 4- plug again to AC 5- wait 5 seconds 6- press on. After 2 days on/sleeping, turn off and another day turn on(more than 1 week overload some efi cache with data about internal processes).

Same issue here, on iMac and Macbook Air (both 2017).

Terrible slow after upgraded to Mac OS Big Sur 11.1.

• iMac (Retina 4K, 21.5-inch, 2017)

• Macbook Air (A1466 MMGF2LL/A)

When Apple will fix this?